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diff --git a/doc/rfc/rfc6830.txt b/doc/rfc/rfc6830.txt new file mode 100644 index 0000000..127017d --- /dev/null +++ b/doc/rfc/rfc6830.txt @@ -0,0 +1,4203 @@ + + + + + + +Internet Engineering Task Force (IETF) D. Farinacci +Request for Comments: 6830 Cisco Systems +Category: Experimental V. Fuller +ISSN: 2070-1721 + D. Meyer + D. Lewis + Cisco Systems + January 2013 + + + The Locator/ID Separation Protocol (LISP) + +Abstract + + This document describes a network-layer-based protocol that enables + separation of IP addresses into two new numbering spaces: Endpoint + Identifiers (EIDs) and Routing Locators (RLOCs). No changes are + required to either host protocol stacks or to the "core" of the + Internet infrastructure. The Locator/ID Separation Protocol (LISP) + can be incrementally deployed, without a "flag day", and offers + Traffic Engineering, multihoming, and mobility benefits to early + adopters, even when there are relatively few LISP-capable sites. + + Design and development of LISP was largely motivated by the problem + statement produced by the October 2006 IAB Routing and Addressing + Workshop. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for examination, experimental implementation, and + evaluation. + + This document defines an Experimental Protocol for the Internet + community. This document is a product of the Internet Engineering + Task Force (IETF). It represents the consensus of the IETF + community. It has received public review and has been approved for + publication by the Internet Engineering Steering Group (IESG). Not + all documents approved by the IESG are a candidate for any level of + Internet Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc6830. + + + + + + + +Farinacci, et al. Experimental [Page 1] + +RFC 6830 LISP January 2013 + + +Copyright Notice + + Copyright (c) 2013 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction ....................................................3 + 2. Requirements Notation ...........................................5 + 3. Definition of Terms .............................................5 + 4. Basic Overview .................................................10 + 4.1. Packet Flow Sequence ......................................13 + 5. LISP Encapsulation Details .....................................15 + 5.1. LISP IPv4-in-IPv4 Header Format ...........................16 + 5.2. LISP IPv6-in-IPv6 Header Format ...........................17 + 5.3. Tunnel Header Field Descriptions ..........................18 + 5.4. Dealing with Large Encapsulated Packets ...................22 + 5.4.1. A Stateless Solution to MTU Handling ...............22 + 5.4.2. A Stateful Solution to MTU Handling ................23 + 5.5. Using Virtualization and Segmentation with LISP ...........24 + 6. EID-to-RLOC Mapping ............................................25 + 6.1. LISP IPv4 and IPv6 Control-Plane Packet Formats ...........25 + 6.1.1. LISP Packet Type Allocations .......................27 + 6.1.2. Map-Request Message Format .........................27 + 6.1.3. EID-to-RLOC UDP Map-Request Message ................30 + 6.1.4. Map-Reply Message Format ...........................31 + 6.1.5. EID-to-RLOC UDP Map-Reply Message ..................35 + 6.1.6. Map-Register Message Format ........................37 + 6.1.7. Map-Notify Message Format ..........................39 + 6.1.8. Encapsulated Control Message Format ................41 + 6.2. Routing Locator Selection .................................42 + 6.3. Routing Locator Reachability ..............................44 + 6.3.1. Echo Nonce Algorithm ...............................46 + 6.3.2. RLOC-Probing Algorithm .............................48 + 6.4. EID Reachability within a LISP Site .......................49 + 6.5. Routing Locator Hashing ...................................49 + + + + + +Farinacci, et al. Experimental [Page 2] + +RFC 6830 LISP January 2013 + + + 6.6. Changing the Contents of EID-to-RLOC Mappings .............50 + 6.6.1. Clock Sweep ........................................51 + 6.6.2. Solicit-Map-Request (SMR) ..........................52 + 6.6.3. Database Map-Versioning ............................53 + 7. Router Performance Considerations ..............................54 + 8. Deployment Scenarios ...........................................55 + 8.1. First-Hop/Last-Hop Tunnel Routers .........................56 + 8.2. Border/Edge Tunnel Routers ................................56 + 8.3. ISP Provider Edge (PE) Tunnel Routers .....................57 + 8.4. LISP Functionality with Conventional NATs .................58 + 8.5. Packets Egressing a LISP Site .............................58 + 9. Traceroute Considerations ......................................58 + 9.1. IPv6 Traceroute ...........................................59 + 9.2. IPv4 Traceroute ...........................................60 + 9.3. Traceroute Using Mixed Locators ...........................60 + 10. Mobility Considerations .......................................61 + 10.1. Site Mobility ............................................61 + 10.2. Slow Endpoint Mobility ...................................61 + 10.3. Fast Endpoint Mobility ...................................61 + 10.4. Fast Network Mobility ....................................63 + 10.5. LISP Mobile Node Mobility ................................64 + 11. Multicast Considerations ......................................64 + 12. Security Considerations .......................................65 + 13. Network Management Considerations .............................67 + 14. IANA Considerations ...........................................67 + 14.1. LISP ACT and Flag Fields .................................67 + 14.2. LISP Address Type Codes ..................................68 + 14.3. LISP UDP Port Numbers ....................................68 + 14.4. LISP Key ID Numbers ......................................68 + 15. Known Open Issues and Areas of Future Work ....................68 + 16. References ....................................................70 + 16.1. Normative References .....................................70 + 16.2. Informative References ...................................71 + Appendix A. Acknowledgments .......................................74 + +1. Introduction + + This document describes the Locator/Identifier Separation Protocol + (LISP), which provides a set of functions for routers to exchange + information used to map from Endpoint Identifiers (EIDs) that are not + globally routable to routable Routing Locators (RLOCs). It also + defines a mechanism for these LISP routers to encapsulate IP packets + addressed with EIDs for transmission across a network infrastructure + that uses RLOCs for routing and forwarding. + + + + + + + +Farinacci, et al. Experimental [Page 3] + +RFC 6830 LISP January 2013 + + + Creation of LISP was initially motivated by discussions during the + IAB-sponsored Routing and Addressing Workshop held in Amsterdam in + October 2006 (see [RFC4984]). A key conclusion of the workshop was + that the Internet routing and addressing system was not scaling well + in the face of the explosive growth of new sites; one reason for this + poor scaling is the increasing number of multihomed sites and other + sites that cannot be addressed as part of topology-based or provider- + based aggregated prefixes. Additional work that more completely + describes the problem statement may be found in [RADIR]. + + A basic observation, made many years ago in early networking research + such as that documented in [CHIAPPA] and [RFC4984], is that using a + single address field for both identifying a device and for + determining where it is topologically located in the network requires + optimization along two conflicting axes: for routing to be efficient, + the address must be assigned topologically; for collections of + devices to be easily and effectively managed, without the need for + renumbering in response to topological change (such as that caused by + adding or removing attachment points to the network or by mobility + events), the address must explicitly not be tied to the topology. + + The approach that LISP takes to solving the routing scalability + problem is to replace IP addresses with two new types of numbers: + Routing Locators (RLOCs), which are topologically assigned to network + attachment points (and are therefore amenable to aggregation) and + used for routing and forwarding of packets through the network; and + Endpoint Identifiers (EIDs), which are assigned independently from + the network topology, are used for numbering devices, and are + aggregated along administrative boundaries. LISP then defines + functions for mapping between the two numbering spaces and for + encapsulating traffic originated by devices using non-routable EIDs + for transport across a network infrastructure that routes and + forwards using RLOCs. Both RLOCs and EIDs are syntactically + identical to IP addresses; it is the semantics of how they are used + that differs. + + This document describes the protocol that implements these functions. + The database that stores the mappings between EIDs and RLOCs is + explicitly a separate "module" to facilitate experimentation with a + variety of approaches. One database design that is being developed + for experimentation as part of the LISP working group work is + [RFC6836]. Others that have been described include [CONS], [EMACS], + and [RFC6837]. Finally, [RFC6833] documents a general-purpose + service interface for accessing a mapping database; this interface is + intended to make the mapping database modular so that different + approaches can be tried without the need to modify installed LISP- + capable devices in LISP sites. + + + + +Farinacci, et al. Experimental [Page 4] + +RFC 6830 LISP January 2013 + + + This experimental specification has areas that require additional + experience and measurement. It is NOT RECOMMENDED for deployment + beyond experimental situations. Results of experimentation may lead + to modifications and enhancements of protocol mechanisms defined in + this document. See Section 15 for specific, known issues that are in + need of further work during development, implementation, and + experimentation. + + An examination of the implications of LISP on Internet traffic, + applications, routers, and security is for future study. This + analysis will explain what role LISP can play in scalable routing and + will also look at scalability and levels of state required for + encapsulation, decapsulation, liveness, and so on. + +2. Requirements Notation + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. + +3. Definition of Terms + + Provider-Independent (PI) Addresses: PI addresses are an address + block assigned from a pool where blocks are not associated with + any particular location in the network (e.g., from a particular + service provider) and are therefore not topologically aggregatable + in the routing system. + + Provider-Assigned (PA) Addresses: PA addresses are an address block + assigned to a site by each service provider to which a site + connects. Typically, each block is a sub-block of a service + provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and + is aggregated into the larger block before being advertised into + the global Internet. Traditionally, IP multihoming has been + implemented by each multihomed site acquiring its own globally + visible prefix. LISP uses only topologically assigned and + aggregatable address blocks for RLOCs, eliminating this + demonstrably non-scalable practice. + + Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 + [RFC2460] address of an Egress Tunnel Router (ETR). An RLOC is + the output of an EID-to-RLOC mapping lookup. An EID maps to one + or more RLOCs. Typically, RLOCs are numbered from topologically + aggregatable blocks that are assigned to a site at each point to + which it attaches to the global Internet; where the topology is + defined by the connectivity of provider networks, RLOCs can be + thought of as PA addresses. Multiple RLOCs can be assigned to the + same ETR device or to multiple ETR devices at a site. + + + +Farinacci, et al. Experimental [Page 5] + +RFC 6830 LISP January 2013 + + + Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for + IPv6) value used in the source and destination address fields of + the first (most inner) LISP header of a packet. The host obtains + a destination EID the same way it obtains a destination address + today, for example, through a Domain Name System (DNS) [RFC1034] + lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. + The source EID is obtained via existing mechanisms used to set a + host's "local" IP address. An EID used on the public Internet + must have the same properties as any other IP address used in that + manner; this means, among other things, that it must be globally + unique. An EID is allocated to a host from an EID-Prefix block + associated with the site where the host is located. An EID can be + used by a host to refer to other hosts. EIDs MUST NOT be used as + LISP RLOCs. Note that EID blocks MAY be assigned in a + hierarchical manner, independent of the network topology, to + facilitate scaling of the mapping database. In addition, an EID + block assigned to a site may have site-local structure + (subnetting) for routing within the site; this structure is not + visible to the global routing system. In theory, the bit string + that represents an EID for one device can represent an RLOC for a + different device. As the architecture is realized, if a given bit + string is both an RLOC and an EID, it must refer to the same + entity in both cases. When used in discussions with other + Locator/ID separation proposals, a LISP EID will be called an + "LEID". Throughout this document, any references to "EID" refer + to an LEID. + + EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are + allocated to a site by an address allocation authority. + EID-Prefixes are associated with a set of RLOC addresses that make + up a "database mapping". EID-Prefix allocations can be broken up + into smaller blocks when an RLOC set is to be associated with the + larger EID-Prefix block. A globally routed address block (whether + PI or PA) is not inherently an EID-Prefix. A globally routed + address block MAY be used by its assignee as an EID block. The + converse is not supported. That is, a site that receives an + explicitly allocated EID-Prefix may not use that EID-Prefix as a + globally routed prefix. This would require coordination and + cooperation with the entities managing the mapping infrastructure. + Once this has been done, that block could be removed from the + globally routed IP system, if other suitable transition and access + mechanisms are in place. Discussion of such transition and access + mechanisms can be found in [RFC6832] and [LISP-DEPLOY]. + + + + + + + + +Farinacci, et al. Experimental [Page 6] + +RFC 6830 LISP January 2013 + + + End-system: An end-system is an IPv4 or IPv6 device that originates + packets with a single IPv4 or IPv6 header. The end-system + supplies an EID value for the destination address field of the IP + header when communicating globally (i.e., outside of its routing + domain). An end-system can be a host computer, a switch or router + device, or any network appliance. + + Ingress Tunnel Router (ITR): An ITR is a router that resides in a + LISP site. Packets sent by sources inside of the LISP site to + destinations outside of the site are candidates for encapsulation + by the ITR. The ITR treats the IP destination address as an EID + and performs an EID-to-RLOC mapping lookup. The router then + prepends an "outer" IP header with one of its globally routable + RLOCs in the source address field and the result of the mapping + lookup in the destination address field. Note that this + destination RLOC MAY be an intermediate, proxy device that has + better knowledge of the EID-to-RLOC mapping closer to the + destination EID. In general, an ITR receives IP packets from site + end-systems on one side and sends LISP-encapsulated IP packets + toward the Internet on the other side. + + Specifically, when a service provider prepends a LISP header for + Traffic Engineering purposes, the router that does this is also + regarded as an ITR. The outer RLOC the ISP ITR uses can be based + on the outer destination address (the originating ITR's supplied + RLOC) or the inner destination address (the originating host's + supplied EID). + + TE-ITR: A TE-ITR is an ITR that is deployed in a service provider + network that prepends an additional LISP header for Traffic + Engineering purposes. + + Egress Tunnel Router (ETR): An ETR is a router that accepts an IP + packet where the destination address in the "outer" IP header is + one of its own RLOCs. The router strips the "outer" header and + forwards the packet based on the next IP header found. In + general, an ETR receives LISP-encapsulated IP packets from the + Internet on one side and sends decapsulated IP packets to site + end-systems on the other side. ETR functionality does not have to + be limited to a router device. A server host can be the endpoint + of a LISP tunnel as well. + + TE-ETR: A TE-ETR is an ETR that is deployed in a service provider + network that strips an outer LISP header for Traffic Engineering + purposes. + + + + + + +Farinacci, et al. Experimental [Page 7] + +RFC 6830 LISP January 2013 + + + xTR: An xTR is a reference to an ITR or ETR when direction of data + flow is not part of the context description. "xTR" refers to the + router that is the tunnel endpoint and is used synonymously with + the term "Tunnel Router". For example, "An xTR can be located at + the Customer Edge (CE) router" indicates both ITR and ETR + functionality at the CE router. + + LISP Router: A LISP router is a router that performs the functions + of any or all of the following: ITR, ETR, Proxy-ITR (PITR), or + Proxy-ETR (PETR). + + EID-to-RLOC Cache: The EID-to-RLOC Cache is a short-lived, + on-demand table in an ITR that stores, tracks, and is responsible + for timing out and otherwise validating EID-to-RLOC mappings. + This cache is distinct from the full "database" of EID-to-RLOC + mappings; it is dynamic, local to the ITR(s), and relatively + small, while the database is distributed, relatively static, and + much more global in scope. + + EID-to-RLOC Database: The EID-to-RLOC Database is a global + distributed database that contains all known EID-Prefix-to-RLOC + mappings. Each potential ETR typically contains a small piece of + the database: the EID-to-RLOC mappings for the EID-Prefixes + "behind" the router. These map to one of the router's own + globally visible IP addresses. The same database mapping entries + MUST be configured on all ETRs for a given site. In a steady + state, the EID-Prefixes for the site and the Locator-Set for each + EID-Prefix MUST be the same on all ETRs. Procedures to enforce + and/or verify this are outside the scope of this document. Note + that there MAY be transient conditions when the EID-Prefix for the + site and Locator-Set for each EID-Prefix may not be the same on + all ETRs. This has no negative implications, since a partial set + of Locators can be used. + + Recursive Tunneling: Recursive Tunneling occurs when a packet has + more than one LISP IP header. Additional layers of tunneling MAY + be employed to implement Traffic Engineering or other re-routing + as needed. When this is done, an additional "outer" LISP header + is added, and the original RLOCs are preserved in the "inner" + header. Any references to tunnels in this specification refer to + dynamic encapsulating tunnels; they are never statically + configured. + + Re-encapsulating Tunnels: Re-encapsulating Tunneling occurs when an + ETR removes a LISP header, then acts as an ITR to prepend another + LISP header. Doing this allows a packet to be re-routed by the + re-encapsulating router without adding the overhead of additional + tunnel headers. Any references to tunnels in this specification + + + +Farinacci, et al. Experimental [Page 8] + +RFC 6830 LISP January 2013 + + + refer to dynamic encapsulating tunnels; they are never statically + configured. When using multiple mapping database systems, care + must be taken to not create re-encapsulation loops through + misconfiguration. + + LISP Header: LISP header is a term used in this document to refer + to the outer IPv4 or IPv6 header, a UDP header, and a LISP- + specific 8-octet header that follow the UDP header and that an ITR + prepends or an ETR strips. + + Address Family Identifier (AFI): AFI is a term used to describe an + address encoding in a packet. An address family currently + pertains to an IPv4 or IPv6 address. See [AFI] and [RFC3232] for + details. An AFI value of 0 used in this specification indicates + an unspecified encoded address where the length of the address is + 0 octets following the 16-bit AFI value of 0. + + Negative Mapping Entry: A negative mapping entry, also known as a + negative cache entry, is an EID-to-RLOC entry where an EID-Prefix + is advertised or stored with no RLOCs. That is, the Locator-Set + for the EID-to-RLOC entry is empty or has an encoded Locator count + of 0. This type of entry could be used to describe a prefix from + a non-LISP site, which is explicitly not in the mapping database. + There are a set of well-defined actions that are encoded in a + Negative Map-Reply (Section 6.1.5). + + Data-Probe: A Data-Probe is a LISP-encapsulated data packet where + the inner-header destination address equals the outer-header + destination address used to trigger a Map-Reply by a decapsulating + ETR. In addition, the original packet is decapsulated and + delivered to the destination host if the destination EID is in the + EID-Prefix range configured on the ETR. Otherwise, the packet is + discarded. A Data-Probe is used in some of the mapping database + designs to "probe" or request a Map-Reply from an ETR; in other + cases, Map-Requests are used. See each mapping database design + for details. When using Data-Probes, by sending Map-Requests on + the underlying routing system, EID-Prefixes must be advertised. + However, this is discouraged if the core is to scale by having + less EID-Prefixes stored in the core router's routing tables. + + Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A + PITR acts like an ITR but does so on behalf of non-LISP sites that + send packets to destinations at LISP sites. + + Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A + PETR acts like an ETR but does so on behalf of LISP sites that + send packets to destinations at non-LISP sites. + + + + +Farinacci, et al. Experimental [Page 9] + +RFC 6830 LISP January 2013 + + + Route-returnability: Route-returnability is an assumption that the + underlying routing system will deliver packets to the destination. + When combined with a nonce that is provided by a sender and + returned by a receiver, this limits off-path data insertion. A + route-returnability check is verified when a message is sent with + a nonce, another message is returned with the same nonce, and the + destination of the original message appears as the source of the + returned message. + + LISP site: LISP site is a set of routers in an edge network that are + under a single technical administration. LISP routers that reside + in the edge network are the demarcation points to separate the + edge network from the core network. + + Client-side: Client-side is a term used in this document to indicate + a connection initiation attempt by an EID. The ITR(s) at the LISP + site are the first to get involved in obtaining database Map-Cache + entries by sending Map-Request messages. + + Server-side: Server-side is a term used in this document to indicate + that a connection initiation attempt is being accepted for a + destination EID. The ETR(s) at the destination LISP site are the + first to send Map-Replies to the source site initiating the + connection. The ETR(s) at this destination site can obtain + mappings by gleaning information from Map-Requests, Data-Probes, + or encapsulated packets. + + Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the + LISP header. They are used by ITRs to inform ETRs about the up/ + down status of all ETRs at the local site. These bits are used as + a hint to convey up/down router status and not path reachability + status. The LSBs can be verified by use of one of the Locator + reachability algorithms described in Section 6.3. + + Anycast Address: Anycast Address is a term used in this document to + refer to the same IPv4 or IPv6 address configured and used on + multiple systems at the same time. An EID or RLOC can be an + anycast address in each of their own address spaces. + +4. Basic Overview + + One key concept of LISP is that end-systems (hosts) operate the same + way they do today. The IP addresses that hosts use for tracking + sockets and connections, and for sending and receiving packets, do + not change. In LISP terminology, these IP addresses are called + Endpoint Identifiers (EIDs). + + + + + +Farinacci, et al. Experimental [Page 10] + +RFC 6830 LISP January 2013 + + + Routers continue to forward packets based on IP destination + addresses. When a packet is LISP encapsulated, these addresses are + referred to as Routing Locators (RLOCs). Most routers along a path + between two hosts will not change; they continue to perform routing/ + forwarding lookups on the destination addresses. For routers between + the source host and the ITR as well as routers from the ETR to the + destination host, the destination address is an EID. For the routers + between the ITR and the ETR, the destination address is an RLOC. + + Another key LISP concept is the "Tunnel Router". A Tunnel Router + prepends LISP headers on host-originated packets and strips them + prior to final delivery to their destination. The IP addresses in + this "outer header" are RLOCs. During end-to-end packet exchange + between two Internet hosts, an ITR prepends a new LISP header to each + packet, and an ETR strips the new header. The ITR performs + EID-to-RLOC lookups to determine the routing path to the ETR, which + has the RLOC as one of its IP addresses. + + Some basic rules governing LISP are: + + o End-systems (hosts) only send to addresses that are EIDs. They + don't know that addresses are EIDs versus RLOCs but assume that + packets get to their intended destinations. In a system where + LISP is deployed, LISP routers intercept EID-addressed packets and + assist in delivering them across the network core where EIDs + cannot be routed. The procedure a host uses to send IP packets + does not change. + + o EIDs are always IP addresses assigned to hosts. + + o LISP routers mostly deal with Routing Locator addresses. See + details in Section 4.1 to clarify what is meant by "mostly". + + o RLOCs are always IP addresses assigned to routers, preferably + topologically oriented addresses from provider CIDR (Classless + Inter-Domain Routing) blocks. + + o When a router originates packets, it may use as a source address + either an EID or RLOC. When acting as a host (e.g., when + terminating a transport session such as Secure SHell (SSH), + TELNET, or the Simple Network Management Protocol (SNMP)), it may + use an EID that is explicitly assigned for that purpose. An EID + that identifies the router as a host MUST NOT be used as an RLOC; + an EID is only routable within the scope of a site. A typical BGP + configuration might demonstrate this "hybrid" EID/RLOC usage where + a router could use its "host-like" EID to terminate iBGP sessions + to other routers in a site while at the same time using RLOCs to + terminate eBGP sessions to routers outside the site. + + + +Farinacci, et al. Experimental [Page 11] + +RFC 6830 LISP January 2013 + + + o Packets with EIDs in them are not expected to be delivered + end-to-end in the absence of an EID-to-RLOC mapping operation. + They are expected to be used locally for intra-site communication + or to be encapsulated for inter-site communication. + + o EID-Prefixes are likely to be hierarchically assigned in a manner + that is optimized for administrative convenience and to facilitate + scaling of the EID-to-RLOC mapping database. The hierarchy is + based on an address allocation hierarchy that is independent of + the network topology. + + o EIDs may also be structured (subnetted) in a manner suitable for + local routing within an Autonomous System (AS). + + An additional LISP header MAY be prepended to packets by a TE-ITR + when re-routing of the path for a packet is desired. A potential + use-case for this would be an ISP router that needs to perform + Traffic Engineering for packets flowing through its network. In such + a situation, termed "Recursive Tunneling", an ISP transit acts as an + additional ITR, and the RLOC it uses for the new prepended header + would be either a TE-ETR within the ISP (along an intra-ISP traffic + engineered path) or a TE-ETR within another ISP (an inter-ISP traffic + engineered path, where an agreement to build such a path exists). + + In order to avoid excessive packet overhead as well as possible + encapsulation loops, this document mandates that a maximum of two + LISP headers can be prepended to a packet. For initial LISP + deployments, it is assumed that two headers is sufficient, where the + first prepended header is used at a site for Location/Identity + separation and the second prepended header is used inside a service + provider for Traffic Engineering purposes. + + Tunnel Routers can be placed fairly flexibly in a multi-AS topology. + For example, the ITR for a particular end-to-end packet exchange + might be the first-hop or default router within a site for the source + host. Similarly, the ETR might be the last-hop router directly + connected to the destination host. Another example, perhaps for a + VPN service outsourced to an ISP by a site, the ITR could be the + site's border router at the service provider attachment point. + Mixing and matching of site-operated, ISP-operated, and other Tunnel + Routers is allowed for maximum flexibility. See Section 8 for more + details. + + + + + + + + + +Farinacci, et al. Experimental [Page 12] + +RFC 6830 LISP January 2013 + + +4.1. Packet Flow Sequence + + This section provides an example of the unicast packet flow with the + following conditions: + + o Source host "host1.abc.example.com" is sending a packet to + "host2.xyz.example.com", exactly what host1 would do if the site + was not using LISP. + + o Each site is multihomed, so each Tunnel Router has an address + (RLOC) assigned from the service provider address block for each + provider to which that particular Tunnel Router is attached. + + o The ITR(s) and ETR(s) are directly connected to the source and + destination, respectively, but the source and destination can be + located anywhere in the LISP site. + + o Map-Requests can be sent on the underlying routing system + topology, to a mapping database system, or directly over an + Alternative Logical Topology [RFC6836]. A Map-Request is sent for + an external destination when the destination is not found in the + forwarding table or matches a default route. + + o Map-Replies are sent on the underlying routing system topology. + + Client host1.abc.example.com wants to communicate with server + host2.xyz.example.com: + + 1. host1.abc.example.com wants to open a TCP connection to + host2.xyz.example.com. It does a DNS lookup on + host2.xyz.example.com. An A/AAAA record is returned. This + address is the destination EID. The locally assigned address of + host1.abc.example.com is used as the source EID. An IPv4 or IPv6 + packet is built and forwarded through the LISP site as a normal + IP packet until it reaches a LISP ITR. + + 2. The LISP ITR must be able to map the destination EID to an RLOC + of one of the ETRs at the destination site. The specific method + used to do this is not described in this example. See [RFC6836] + or [CONS] for possible solutions. + + 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be + rate-limited. + + + + + + + + +Farinacci, et al. Experimental [Page 13] + +RFC 6830 LISP January 2013 + + + 4. When an alternate mapping system is not in use, the Map-Request + packet is routed through the underlying routing system. + Otherwise, the Map-Request packet is routed on an alternate + logical topology, for example, the [RFC6836] database mapping + system. In either case, when the Map-Request arrives at one of + the ETRs at the destination site, it will process the packet as a + control message. + + 5. The ETR looks at the destination EID of the Map-Request and + matches it against the prefixes in the ETR's configured + EID-to-RLOC mapping database. This is the list of EID-Prefixes + the ETR is supporting for the site it resides in. If there is no + match, the Map-Request is dropped. Otherwise, a LISP Map-Reply + is returned to the ITR. + + 6. The ITR receives the Map-Reply message, parses the message (to + check for format validity), and stores the mapping information + from the packet. This information is stored in the ITR's + EID-to-RLOC mapping cache. Note that the map-cache is an + on-demand cache. An ITR will manage its map-cache in such a way + that optimizes for its resource constraints. + + 7. Subsequent packets from host1.abc.example.com to + host2.xyz.example.com will have a LISP header prepended by the + ITR using the appropriate RLOC as the LISP header destination + address learned from the ETR. Note that the packet MAY be sent + to a different ETR than the one that returned the Map-Reply due + to the source site's hashing policy or the destination site's + Locator-Set policy. + + 8. The ETR receives these packets directly (since the destination + address is one of its assigned IP addresses), checks the validity + of the addresses, strips the LISP header, and forwards packets to + the attached destination host. + + In order to defer the need for a mapping lookup in the reverse + direction, an ETR MAY create a cache entry that maps the source EID + (inner-header source IP address) to the source RLOC (outer-header + source IP address) in a received LISP packet. Such a cache entry is + termed a "gleaned" mapping and only contains a single RLOC for the + EID in question. More complete information about additional RLOCs + SHOULD be verified by sending a LISP Map-Request for that EID. Both + the ITR and the ETR may also influence the decision the other makes + in selecting an RLOC. See Section 6 for more details. + + + + + + + +Farinacci, et al. Experimental [Page 14] + +RFC 6830 LISP January 2013 + + +5. LISP Encapsulation Details + + Since additional tunnel headers are prepended, the packet becomes + larger and can exceed the MTU of any link traversed from the ITR to + the ETR. It is RECOMMENDED in IPv4 that packets do not get + fragmented as they are encapsulated by the ITR. Instead, the packet + is dropped and an ICMP Too Big message is returned to the source. + + This specification RECOMMENDS that implementations provide support + for one of the proposed fragmentation and reassembly schemes. Two + existing schemes are detailed in Section 5.4. + + Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP + architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner + header is in IPv4 packet format and the outer header is in IPv6 + packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header + is in IPv6 packet format and the outer header is in IPv4 packet + format). The next sub-sections illustrate packet formats for the + homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 + combinations MUST be supported. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 15] + +RFC 6830 LISP January 2013 + + +5.1. LISP IPv4-in-IPv4 Header Format + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / |Version| IHL |Type of Service| Total Length | + / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Identification |Flags| Fragment Offset | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + OH | Time to Live | Protocol = 17 | Header Checksum | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Source Routing Locator | + \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | Destination Routing Locator | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port = xxxx | Dest Port = 4341 | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + L |N|L|E|V|I|flags| Nonce/Map-Version | + I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + S / | Instance ID/Locator-Status-Bits | + P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / |Version| IHL |Type of Service| Total Length | + / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Identification |Flags| Fragment Offset | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + IH | Time to Live | Protocol | Header Checksum | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Source EID | + \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | Destination EID | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + IHL = IP-Header-Length + + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 16] + +RFC 6830 LISP January 2013 + + +5.2. LISP IPv6-in-IPv6 Header Format + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / |Version| Traffic Class | Flow Label | + / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Payload Length | Next Header=17| Hop Limit | + v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + O + + + u | | + t + Source Routing Locator + + e | | + r + + + | | + H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + d | | + r + + + | | + ^ + Destination Routing Locator + + | | | + \ + + + \ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port = xxxx | Dest Port = 4341 | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + L |N|L|E|V|I|flags| Nonce/Map-Version | + I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + S / | Instance ID/Locator-Status-Bits | + P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / |Version| Traffic Class | Flow Label | + / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Payload Length | Next Header | Hop Limit | + v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 17] + +RFC 6830 LISP January 2013 + + + | | + I + + + n | | + n + Source EID + + e | | + r + + + | | + H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + d | | + r + + + | | + ^ + Destination EID + + \ | | + \ + + + \ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +5.3. Tunnel Header Field Descriptions + + Inner Header (IH): The inner header is the header on the datagram + received from the originating host. The source and destination IP + addresses are EIDs [RFC0791] [RFC2460]. + + Outer Header: (OH) The outer header is a new header prepended by an + ITR. The address fields contain RLOCs obtained from the ingress + router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" + from [RFC0768]. The setting of the Don't Fragment (DF) bit + 'Flags' field is according to rules listed in Sections 5.4.1 and + 5.4.2. + + UDP Header: The UDP header contains an ITR selected source port when + encapsulating a packet. See Section 6.5 for details on the hash + algorithm used to select a source port based on the 5-tuple of the + inner header. The destination port MUST be set to the well-known + IANA-assigned port value 4341. + + UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero + by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation + [UDP-TUNNELS] [UDP-ZERO]. When a packet with a zero UDP checksum + is received by an ETR, the ETR MUST accept the packet for + decapsulation. When an ITR transmits a non-zero value for the UDP + checksum, it MUST send a correctly computed value in this field. + When an ETR receives a packet with a non-zero UDP checksum, it MAY + choose to verify the checksum value. If it chooses to perform + such verification, and the verification fails, the packet MUST be + silently dropped. If the ETR chooses not to perform the + verification, or performs the verification successfully, the + packet MUST be accepted for decapsulation. The handling of UDP + + + +Farinacci, et al. Experimental [Page 18] + +RFC 6830 LISP January 2013 + + + checksums for all tunneling protocols, including LISP, is under + active discussion within the IETF. When that discussion + concludes, any necessary changes will be made to align LISP with + the outcome of the broader discussion. + + UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated + packet to be the sum of the inner-header IPv4 Total Length plus + the UDP and LISP header lengths. For an IPv6-encapsulated packet, + the 'UDP Length' field is the sum of the inner-header IPv6 Payload + Length, the size of the IPv6 header (40 octets), and the size of + the UDP and LISP headers. + + N: The N-bit is the nonce-present bit. When this bit is set to 1, + the low-order 24 bits of the first 32 bits of the LISP header + contain a Nonce. See Section 6.3.1 for details. Both N- and + V-bits MUST NOT be set in the same packet. If they are, a + decapsulating ETR MUST treat the 'Nonce/Map-Version' field as + having a Nonce value present. + + L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When + this bit is set to 1, the Locator-Status-Bits in the second + 32 bits of the LISP header are in use. + + x 1 x x 0 x x x + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |N|L|E|V|I|flags| Nonce/Map-Version | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Locator-Status-Bits | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored + and has no meaning when the N-bit is set to 0. When the N-bit is + set to 1 and this bit is set to 1, an ITR is requesting that the + nonce value in the 'Nonce' field be echoed back in LISP- + encapsulated packets when the ITR is also an ETR. See + Section 6.3.1 for details. + + V: The V-bit is the Map-Version present bit. When this bit is set to + 1, the N-bit MUST be 0. Refer to Section 6.6.3 for more details. + This bit indicates that the LISP header is encoded in this + case as: + + 0 x 0 1 x x x x + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Instance ID/Locator-Status-Bits | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + +Farinacci, et al. Experimental [Page 19] + +RFC 6830 LISP January 2013 + + + I: The I-bit is the Instance ID bit. See Section 5.5 for more + details. When this bit is set to 1, the 'Locator-Status-Bits' + field is reduced to 8 bits and the high-order 24 bits are used as + an Instance ID. If the L-bit is set to 0, then the low-order + 8 bits are transmitted as zero and ignored on receipt. The format + of the LISP header would look like this: + + x x x x 1 x x x + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |N|L|E|V|I|flags| Nonce/Map-Version | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Instance ID | LSBs | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + flags: The 'flags' field is a 3-bit field reserved for future flag + use. It MUST be set to 0 on transmit and MUST be ignored on + receipt. + + LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is + randomly generated by an ITR when the N-bit is set to 1. Nonce + generation algorithms are an implementation matter but are + required to generate different nonces when sending to different + destinations. However, the same nonce can be used for a period of + time to the same destination. The nonce is also used when the + E-bit is set to request the nonce value to be echoed by the other + side when packets are returned. When the E-bit is clear but the + N-bit is set, a remote ITR is either echoing a previously + requested echo-nonce or providing a random nonce. See + Section 6.3.1 for more details. + + LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the + 'Locator-Status-Bits' field in the LISP header is set by an ITR to + indicate to an ETR the up/down status of the Locators in the + source site. Each RLOC in a Map-Reply is assigned an ordinal + value from 0 to n-1 (when there are n RLOCs in a mapping entry). + The Locator-Status-Bits are numbered from 0 to n-1 from the least + significant bit of the field. The field is 32 bits when the I-bit + is set to 0 and is 8 bits when the I-bit is set to 1. When a + Locator-Status-Bit is set to 1, the ITR is indicating to the ETR + that the RLOC associated with the bit ordinal has up status. See + Section 6.3 for details on how an ITR can determine the status of + the ETRs at the same site. When a site has multiple EID-Prefixes + that result in multiple mappings (where each could have a + different Locator-Set), the Locator-Status-Bits setting in an + encapsulated packet MUST reflect the mapping for the EID-Prefix + that the inner-header source EID address matches. If the LSB for + an anycast Locator is set to 1, then there is at least one RLOC + with that address, and the ETR is considered 'up'. + + + +Farinacci, et al. Experimental [Page 20] + +RFC 6830 LISP January 2013 + + + When doing ITR/PITR encapsulation: + + o The outer-header 'Time to Live' field (or 'Hop Limit' field, in + the case of IPv6) SHOULD be copied from the inner-header 'Time to + Live' field. + + o The outer-header 'Type of Service' field (or the 'Traffic Class' + field, in the case of IPv6) SHOULD be copied from the inner-header + 'Type of Service' field (with one exception; see below). + + When doing ETR/PETR decapsulation: + + o The inner-header 'Time to Live' field (or 'Hop Limit' field, in + the case of IPv6) SHOULD be copied from the outer-header 'Time to + Live' field, when the Time to Live value of the outer header is + less than the Time to Live value of the inner header. Failing to + perform this check can cause the Time to Live of the inner header + to increment across encapsulation/decapsulation cycles. This + check is also performed when doing initial encapsulation, when a + packet comes to an ITR or PITR destined for a LISP site. + + o The inner-header 'Type of Service' field (or the 'Traffic Class' + field, in the case of IPv6) SHOULD be copied from the outer-header + 'Type of Service' field (with one exception; see below). + + Note that if an ETR/PETR is also an ITR/PITR and chooses to + re-encapsulate after decapsulating, the net effect of this is that + the new outer header will carry the same Time to Live as the old + outer header minus 1. + + Copying the Time to Live (TTL) serves two purposes: first, it + preserves the distance the host intended the packet to travel; + second, and more importantly, it provides for suppression of looping + packets in the event there is a loop of concatenated tunnels due to + misconfiguration. See Section 9.3 for TTL exception handling for + traceroute packets. + + The Explicit Congestion Notification ('ECN') field occupies bits 6 + and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic + Class' field [RFC3168]. The 'ECN' field requires special treatment + in order to avoid discarding indications of congestion [RFC3168]. + ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner + header to the outer header. Re-encapsulation MUST copy the 2-bit + 'ECN' field from the stripped outer header to the new outer header. + If the 'ECN' field contains a congestion indication codepoint (the + value is '11', the Congestion Experienced (CE) codepoint), then ETR + decapsulation MUST copy the 2-bit 'ECN' field from the stripped outer + header to the surviving inner header that is used to forward the + + + +Farinacci, et al. Experimental [Page 21] + +RFC 6830 LISP January 2013 + + + packet beyond the ETR. These requirements preserve CE indications + when a packet that uses ECN traverses a LISP tunnel and becomes + marked with a CE indication due to congestion between the tunnel + endpoints. + +5.4. Dealing with Large Encapsulated Packets + + This section proposes two mechanisms to deal with packets that exceed + the path MTU between the ITR and ETR. + + It is left to the implementor to decide if the stateless or stateful + mechanism should be implemented. Both or neither can be used, since + it is a local decision in the ITR regarding how to deal with MTU + issues, and sites can interoperate with differing mechanisms. + + Both stateless and stateful mechanisms also apply to Re-encapsulating + and Recursive Tunneling, so any actions below referring to an ITR + also apply to a TE-ITR. + +5.4.1. A Stateless Solution to MTU Handling + + An ITR stateless solution to handle MTU issues is described as + follows: + + 1. Define H to be the size, in octets, of the outer header an ITR + prepends to a packet. This includes the UDP and LISP header + lengths. + + 2. Define L to be the size, in octets, of the maximum-sized packet + an ITR can send to an ETR without the need for the ITR or any + intermediate routers to fragment the packet. + + 3. Define an architectural constant S for the maximum size of a + packet, in octets, an ITR must receive so the effective MTU can + be met. That is, S = L - H. + + When an ITR receives a packet from a site-facing interface and adds H + octets worth of encapsulation to yield a packet size greater than L + octets, it resolves the MTU issue by first splitting the original + packet into 2 equal-sized fragments. A LISP header is then prepended + to each fragment. The size of the encapsulated fragments is then + (S/2 + H), which is less than the ITR's estimate of the path MTU + between the ITR and its correspondent ETR. + + When an ETR receives encapsulated fragments, it treats them as two + individually encapsulated packets. It strips the LISP headers and + then forwards each fragment to the destination host of the + destination site. The two fragments are reassembled at the + + + +Farinacci, et al. Experimental [Page 22] + +RFC 6830 LISP January 2013 + + + destination host into the single IP datagram that was originated by + the source host. Note that reassembly can happen at the ETR if the + encapsulated packet was fragmented at or after the ITR. + + This behavior is performed by the ITR when the source host originates + a packet with the 'DF' field of the IP header set to 0. When the + 'DF' field of the IP header is set to 1, or the packet is an IPv6 + packet originated by the source host, the ITR will drop the packet + when the size is greater than L and send an ICMP Too Big message to + the source with a value of S, where S is (L - H). + + When the outer-header encapsulation uses an IPv4 header, an + implementation SHOULD set the DF bit to 1 so ETR fragment reassembly + can be avoided. An implementation MAY set the DF bit in such headers + to 0 if it has good reason to believe there are unresolvable path MTU + issues between the sending ITR and the receiving ETR. + + This specification RECOMMENDS that L be defined as 1500. + +5.4.2. A Stateful Solution to MTU Handling + + An ITR stateful solution to handle MTU issues is described as follows + and was first introduced in [OPENLISP]: + + 1. The ITR will keep state of the effective MTU for each Locator per + Map-Cache entry. The effective MTU is what the core network can + deliver along the path between the ITR and ETR. + + 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet + with the DF bit set to 1, exceeds what the core network can + deliver, one of the intermediate routers on the path will send an + ICMP Too Big message to the ITR. The ITR will parse the ICMP + message to determine which Locator is affected by the effective + MTU change and then record the new effective MTU value in the + Map-Cache entry. + + 3. When a packet is received by the ITR from a source inside of the + site and the size of the packet is greater than the effective MTU + stored with the Map-Cache entry associated with the destination + EID the packet is for, the ITR will send an ICMP Too Big message + back to the source. The packet size advertised by the ITR in the + ICMP Too Big message is the effective MTU minus the LISP + encapsulation length. + + Even though this mechanism is stateful, it has advantages over the + stateless IP fragmentation mechanism, by not involving the + destination host with reassembly of ITR fragmented packets. + + + + +Farinacci, et al. Experimental [Page 23] + +RFC 6830 LISP January 2013 + + +5.5. Using Virtualization and Segmentation with LISP + + When multiple organizations inside of a LISP site are using private + addresses [RFC1918] as EID-Prefixes, their address spaces MUST remain + segregated due to possible address duplication. An Instance ID in + the address encoding can aid in making the entire AFI-based address + unique. See IANA Considerations (Section 14.2) for details on + possible address encodings. + + An Instance ID can be carried in a LISP-encapsulated packet. An ITR + that prepends a LISP header will copy a 24-bit value used by the LISP + router to uniquely identify the address space. The value is copied + to the 'Instance ID' field of the LISP header, and the I-bit is set + to 1. + + When an ETR decapsulates a packet, the Instance ID from the LISP + header is used as a table identifier to locate the forwarding table + to use for the inner destination EID lookup. + + For example, an 802.1Q VLAN tag or VPN identifier could be used as a + 24-bit Instance ID. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 24] + +RFC 6830 LISP January 2013 + + +6. EID-to-RLOC Mapping + +6.1. LISP IPv4 and IPv6 Control-Plane Packet Formats + + The following UDP packet formats are used by the LISP control plane. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Version| IHL |Type of Service| Total Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Identification |Flags| Fragment Offset | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Time to Live | Protocol = 17 | Header Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Source Routing Locator | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Destination Routing Locator | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port | Dest Port | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + | LISP Message | + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + + + + + + + + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 25] + +RFC 6830 LISP January 2013 + + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Version| Traffic Class | Flow Label | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Payload Length | Next Header=17| Hop Limit | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + + + + | | + + Source Routing Locator + + | | + + + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + + + + | | + + Destination Routing Locator + + | | + + + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port | Dest Port | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | + | LISP Message | + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + The LISP UDP-based messages are the Map-Request and Map-Reply + messages. When a UDP Map-Request is sent, the UDP source port is + chosen by the sender and the destination UDP port number is set to + 4342. When a UDP Map-Reply is sent, the source UDP port number is + set to 4342 and the destination UDP port number is copied from the + source port of either the Map-Request or the invoking data packet. + Implementations MUST be prepared to accept packets when either the + source port or destination UDP port is set to 4342 due to NATs + changing port number values. + + The 'UDP Length' field will reflect the length of the UDP header and + the LISP Message payload. + + + + + + + +Farinacci, et al. Experimental [Page 26] + +RFC 6830 LISP January 2013 + + + The UDP checksum is computed and set to non-zero for Map-Request, + Map-Reply, Map-Register, and Encapsulated Control Message (ECM) + control messages. It MUST be checked on receipt, and if the checksum + fails, the packet MUST be dropped. + + The format of control messages includes the UDP header so the + checksum and length fields can be used to protect and delimit message + boundaries. + +6.1.1. LISP Packet Type Allocations + + This section will be the authoritative source for allocating LISP + Type values and for defining LISP control message formats. Current + allocations are: + + Reserved: 0 b'0000' + LISP Map-Request: 1 b'0001' + LISP Map-Reply: 2 b'0010' + LISP Map-Register: 3 b'0011' + LISP Map-Notify: 4 b'0100' + LISP Encapsulated Control Message: 8 b'1000' + +6.1.2. Map-Request Message Format + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Type=1 |A|M|P|S|p|s| Reserved | IRC | Record Count | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Nonce . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | . . . Nonce | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Source-EID-AFI | Source EID Address ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | ITR-RLOC-AFI n | ITR-RLOC Address n ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Reserved | EID mask-len | EID-Prefix-AFI | + Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | EID-Prefix ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Map-Reply Record ... | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + + +Farinacci, et al. Experimental [Page 27] + +RFC 6830 LISP January 2013 + + + Packet field descriptions: + + Type: 1 (Map-Request) + + A: This is an authoritative bit, which is set to 0 for UDP-based + Map-Requests sent by an ITR. It is set to 1 when an ITR wants the + destination site to return the Map-Reply rather than the mapping + database system. + + M: This is the map-data-present bit. When set, it indicates that a + Map-Reply Record segment is included in the Map-Request. + + P: This is the probe-bit, which indicates that a Map-Request SHOULD + be treated as a Locator reachability probe. The receiver SHOULD + respond with a Map-Reply with the probe-bit set, indicating that + the Map-Reply is a Locator reachability probe reply, with the + nonce copied from the Map-Request. See Section 6.3.2 for more + details. + + S: This is the Solicit-Map-Request (SMR) bit. See Section 6.6.2 for + details. + + p: This is the PITR bit. This bit is set to 1 when a PITR sends a + Map-Request. + + s: This is the SMR-invoked bit. This bit is set to 1 when an xTR is + sending a Map-Request in response to a received SMR-based + Map-Request. + + Reserved: This field MUST be set to 0 on transmit and MUST be + ignored on receipt. + + IRC: This 5-bit field is the ITR-RLOC Count, which encodes the + additional number of ('ITR-RLOC-AFI', 'ITR-RLOC Address') fields + present in this message. At least one (ITR-RLOC-AFI, + ITR-RLOC-Address) pair MUST be encoded. Multiple 'ITR-RLOC + Address' fields are used, so a Map-Replier can select which + destination address to use for a Map-Reply. The IRC value ranges + from 0 to 31. For a value of 0, there is 1 ITR-RLOC address + encoded; for a value of 1, there are 2 ITR-RLOC addresses encoded, + and so on up to 31, which encodes a total of 32 ITR-RLOC + addresses. + + Record Count: This is the number of records in this Map-Request + message. A record is comprised of the portion of the packet that + is labeled 'Rec' above and occurs the number of times equal to + Record Count. For this version of the protocol, a receiver MUST + accept and process Map-Requests that contain one or more records, + + + +Farinacci, et al. Experimental [Page 28] + +RFC 6830 LISP January 2013 + + + but a sender MUST only send Map-Requests containing one record. + Support for requesting multiple EIDs in a single Map-Request + message will be specified in a future version of the protocol. + + Nonce: This is an 8-octet random value created by the sender of the + Map-Request. This nonce will be returned in the Map-Reply. The + security of the LISP mapping protocol critically depends on the + strength of the nonce in the Map-Request message. The nonce + SHOULD be generated by a properly seeded pseudo-random (or strong + random) source. See [RFC4086] for advice on generating security- + sensitive random data. + + Source-EID-AFI: This is the address family of the 'Source EID + Address' field. + + Source EID Address: This is the EID of the source host that + originated the packet that caused the Map-Request. When + Map-Requests are used for refreshing a Map-Cache entry or for + RLOC-Probing, an AFI value 0 is used and this field is of zero + length. + + ITR-RLOC-AFI: This is the address family of the 'ITR-RLOC Address' + field that follows this field. + + ITR-RLOC Address: This is used to give the ETR the option of + selecting the destination address from any address family for the + Map-Reply message. This address MUST be a routable RLOC address + of the sender of the Map-Request message. + + EID mask-len: This is the mask length for the EID-Prefix. + + EID-Prefix-AFI: This is the address family of the EID-Prefix + according to [AFI]. + + EID-Prefix: This prefix is 4 octets for an IPv4 address family and + 16 octets for an IPv6 address family. When a Map-Request is sent + by an ITR because a data packet is received for a destination + where there is no mapping entry, the EID-Prefix is set to the + destination IP address of the data packet, and the 'EID mask-len' + is set to 32 or 128 for IPv4 or IPv6, respectively. When an xTR + wants to query a site about the status of a mapping it already has + cached, the EID-Prefix used in the Map-Request has the same mask + length as the EID-Prefix returned from the site when it sent a + Map-Reply message. + + + + + + + +Farinacci, et al. Experimental [Page 29] + +RFC 6830 LISP January 2013 + + + Map-Reply Record: When the M-bit is set, this field is the size of a + single "Record" in the Map-Reply format. This Map-Reply record + contains the EID-to-RLOC mapping entry associated with the Source + EID. This allows the ETR that will receive this Map-Request to + cache the data if it chooses to do so. + +6.1.3. EID-to-RLOC UDP Map-Request Message + + A Map-Request is sent from an ITR when it needs a mapping for an EID, + wants to test an RLOC for reachability, or wants to refresh a mapping + before TTL expiration. For the initial case, the destination IP + address used for the Map-Request is the data packet's destination + address (i.e., the destination EID) that had a mapping cache lookup + failure. For the latter two cases, the destination IP address used + for the Map-Request is one of the RLOC addresses from the Locator-Set + of the Map-Cache entry. The source address is either an IPv4 or IPv6 + RLOC address, depending on whether the Map-Request is using an IPv4 + or IPv6 header, respectively. In all cases, the UDP source port + number for the Map-Request message is a 16-bit value selected by the + ITR/PITR, and the UDP destination port number is set to the well- + known destination port number 4342. A successful Map-Reply, which is + one that has a nonce that matches an outstanding Map-Request nonce, + will update the cached set of RLOCs associated with the EID-Prefix + range. + + One or more Map-Request ('ITR-RLOC-AFI', 'ITR-RLOC-Address') fields + MUST be filled in by the ITR. The number of fields (minus 1) encoded + MUST be placed in the 'IRC' field. The ITR MAY include all locally + configured Locators in this list or just provide one locator address + from each address family it supports. If the ITR erroneously + provides no ITR-RLOC addresses, the Map-Replier MUST drop the + Map-Request. + + Map-Requests can also be LISP encapsulated using UDP destination + port 4342 with a LISP Type value set to "Encapsulated Control + Message", when sent from an ITR to a Map-Resolver. Likewise, + Map-Requests are LISP encapsulated the same way from a Map-Server to + an ETR. Details on Encapsulated Map-Requests and Map-Resolvers can + be found in [RFC6833]. + + Map-Requests MUST be rate-limited. It is RECOMMENDED that a + Map-Request for the same EID-Prefix be sent no more than once per + second. + + An ITR that is configured with mapping database information (i.e., it + is also an ETR) MAY optionally include those mappings in a + Map-Request. When an ETR configured to accept and verify such + "piggybacked" mapping data receives such a Map-Request and it does + + + +Farinacci, et al. Experimental [Page 30] + +RFC 6830 LISP January 2013 + + + not have this mapping in the map-cache, it MAY originate a "verifying + Map-Request", addressed to the map-requesting ITR and the ETR MAY add + a Map-Cache entry. If the ETR has a Map-Cache entry that matches the + "piggybacked" EID and the RLOC is in the Locator-Set for the entry, + then it may send the "verifying Map-Request" directly to the + originating Map-Request source. If the RLOC is not in the + Locator-Set, then the ETR MUST send the "verifying Map-Request" to + the "piggybacked" EID. Doing this forces the "verifying Map-Request" + to go through the mapping database system to reach the authoritative + source of information about that EID, guarding against RLOC-spoofing + in the "piggybacked" mapping data. + +6.1.4. Map-Reply Message Format + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Type=2 |P|E|S| Reserved | Record Count | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Nonce . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | . . . Nonce | + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Record TTL | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + R | Locator Count | EID mask-len | ACT |A| Reserved | + e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + c | Rsvd | Map-Version Number | EID-Prefix-AFI | + o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + r | EID-Prefix | + d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | /| Priority | Weight | M Priority | M Weight | + | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | o | Unused Flags |L|p|R| Loc-AFI | + | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | \| Locator | + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 31] + +RFC 6830 LISP January 2013 + + + Packet field descriptions: + + Type: 2 (Map-Reply) + + P: This is the probe-bit, which indicates that the Map-Reply is in + response to a Locator reachability probe Map-Request. The 'Nonce' + field MUST contain a copy of the nonce value from the original + Map-Request. See Section 6.3.2 for more details. + + E: This bit indicates that the ETR that sends this Map-Reply message + is advertising that the site is enabled for the Echo-Nonce Locator + reachability algorithm. See Section 6.3.1 for more details. + + S: This is the Security bit. When set to 1, the following + authentication information will be appended to the end of the + Map-Reply. The detailed format of the Authentication Data Content + is for further study. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | AD Type | Authentication Data Content . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Reserved: This field MUST be set to 0 on transmit and MUST be + ignored on receipt. + + Record Count: This is the number of records in this reply message. + A record is comprised of that portion of the packet labeled + 'Record' above and occurs the number of times equal to Record + Count. + + Nonce: This is a 24-bit value set in a Data-Probe packet, or a + 64-bit value from the Map-Request is echoed in this 'Nonce' field + of the Map-Reply. When a 24-bit value is supplied, it resides in + the low-order 64 bits of the 'Nonce' field. + + Record TTL: This is the time in minutes the recipient of the + Map-Reply will store the mapping. If the TTL is 0, the entry + SHOULD be removed from the cache immediately. If the value is + 0xffffffff, the recipient can decide locally how long to store the + mapping. + + Locator Count: This is the number of Locator entries. A Locator + entry comprises what is labeled above as 'Loc'. The Locator count + can be 0, indicating that there are no Locators for the + EID-Prefix. + + + + +Farinacci, et al. Experimental [Page 32] + +RFC 6830 LISP January 2013 + + + EID mask-len: This is the mask length for the EID-Prefix. + + ACT: This 3-bit field describes Negative Map-Reply actions. In any + other message type, these bits are set to 0 and ignored on + receipt. These bits are used only when the 'Locator Count' field + is set to 0. The action bits are encoded only in Map-Reply + messages. The actions defined are used by an ITR or PITR when a + destination EID matches a negative Map-Cache entry. Unassigned + values should cause a Map-Cache entry to be created, and when + packets match this negative cache entry, they will be dropped. + The current assigned values are: + + (0) No-Action: The map-cache is kept alive, and no packet + encapsulation occurs. + + (1) Natively-Forward: The packet is not encapsulated or dropped + but natively forwarded. + + (2) Send-Map-Request: The packet invokes sending a Map-Request. + + (3) Drop: A packet that matches this map-cache entry is dropped. + An ICMP Destination Unreachable message SHOULD be sent. + + A: The Authoritative bit, when sent, is always set to 1 by an ETR. + When a Map-Server is proxy Map-Replying [RFC6833] for a LISP site, + the Authoritative bit is set to 0. This indicates to requesting + ITRs that the Map-Reply was not originated by a LISP node managed + at the site that owns the EID-Prefix. + + Map-Version Number: When this 12-bit value is non-zero, the + Map-Reply sender is informing the ITR what the version number is + for the EID record contained in the Map-Reply. The ETR can + allocate this number internally but MUST coordinate this value + with other ETRs for the site. When this value is 0, there is no + versioning information conveyed. The Map-Version Number can be + included in Map-Request and Map-Register messages. See + Section 6.6.3 for more details. + + EID-Prefix-AFI: Address family of the EID-Prefix according to [AFI]. + + EID-Prefix: This prefix is 4 octets for an IPv4 address family and + 16 octets for an IPv6 address family. + + Priority: Each RLOC is assigned a unicast Priority. Lower values + are more preferable. When multiple RLOCs have the same Priority, + they MAY be used in a load-split fashion. A value of 255 means + the RLOC MUST NOT be used for unicast forwarding. + + + + +Farinacci, et al. Experimental [Page 33] + +RFC 6830 LISP January 2013 + + + Weight: When priorities are the same for multiple RLOCs, the Weight + indicates how to balance unicast traffic between them. Weight is + encoded as a relative weight of total unicast packets that match + the mapping entry. For example, if there are 4 Locators in a + Locator-Set, where the Weights assigned are 30, 20, 20, and 10, + the first Locator will get 37.5% of the traffic, the 2nd and 3rd + Locators will get 25% of the traffic, and the 4th Locator will get + 12.5% of the traffic. If all Weights for a Locator-Set are equal, + the receiver of the Map-Reply will decide how to load-split the + traffic. See Section 6.5 for a suggested hash algorithm to + distribute the load across Locators with the same Priority and + equal Weight values. + + M Priority: Each RLOC is assigned a multicast Priority used by an + ETR in a receiver multicast site to select an ITR in a source + multicast site for building multicast distribution trees. A value + of 255 means the RLOC MUST NOT be used for joining a multicast + distribution tree. For more details, see [RFC6831]. + + M Weight: When priorities are the same for multiple RLOCs, the + Weight indicates how to balance building multicast distribution + trees across multiple ITRs. The Weight is encoded as a relative + weight (similar to the unicast Weights) of the total number of + trees built to the source site identified by the EID-Prefix. If + all Weights for a Locator-Set are equal, the receiver of the + Map-Reply will decide how to distribute multicast state across + ITRs. For more details, see [RFC6831]. + + Unused Flags: These are set to 0 when sending and ignored on + receipt. + + L: When this bit is set, the Locator is flagged as a local Locator to + the ETR that is sending the Map-Reply. When a Map-Server is doing + proxy Map-Replying [RFC6833] for a LISP site, the L-bit is set to + 0 for all Locators in this Locator-Set. + + p: When this bit is set, an ETR informs the RLOC-Probing ITR that the + locator address for which this bit is set is the one being + RLOC-probed and MAY be different from the source address of the + Map-Reply. An ITR that RLOC-probes a particular Locator MUST use + this Locator for retrieving the data structure used to store the + fact that the Locator is reachable. The p-bit is set for a single + Locator in the same Locator-Set. If an implementation sets more + than one p-bit erroneously, the receiver of the Map-Reply MUST + select the first Locator. The p-bit MUST NOT be set for + Locator-Set records sent in Map-Request and Map-Register messages. + + + + + +Farinacci, et al. Experimental [Page 34] + +RFC 6830 LISP January 2013 + + + R: This is set when the sender of a Map-Reply has a route to the + Locator in the Locator data record. This receiver may find this + useful to know if the Locator is up but not necessarily reachable + from the receiver's point of view. See also Section 6.4 for + another way the R-bit may be used. + + Locator: This is an IPv4 or IPv6 address (as encoded by the + 'Loc-AFI' field) assigned to an ETR. Note that the destination + RLOC address MAY be an anycast address. A source RLOC can be an + anycast address as well. The source or destination RLOC MUST NOT + be the broadcast address (255.255.255.255 or any subnet broadcast + address known to the router) and MUST NOT be a link-local + multicast address. The source RLOC MUST NOT be a multicast + address. The destination RLOC SHOULD be a multicast address if it + is being mapped from a multicast destination EID. + +6.1.5. EID-to-RLOC UDP Map-Reply Message + + A Map-Reply returns an EID-Prefix with a prefix length that is less + than or equal to the EID being requested. The EID being requested is + either from the destination field of an IP header of a Data-Probe or + the EID record of a Map-Request. The RLOCs in the Map-Reply are + globally routable IP addresses of all ETRs for the LISP site. Each + RLOC conveys status reachability but does not convey path + reachability from a requester's perspective. Separate testing of + path reachability is required. See Section 6.3 for details. + + Note that a Map-Reply may contain different EID-Prefix granularity + (prefix + length) than the Map-Request that triggers it. This might + occur if a Map-Request were for a prefix that had been returned by an + earlier Map-Reply. In such a case, the requester updates its cache + with the new prefix information and granularity. For example, a + requester with two cached EID-Prefixes that are covered by a + Map-Reply containing one less-specific prefix replaces the entry with + the less-specific EID-Prefix. Note that the reverse, replacement of + one less-specific prefix with multiple more-specific prefixes, can + also occur, not by removing the less-specific prefix but rather by + adding the more-specific prefixes that, during a lookup, will + override the less-specific prefix. + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 35] + +RFC 6830 LISP January 2013 + + + When an ETR is configured with overlapping EID-Prefixes, a + Map-Request with an EID that best matches any EID-Prefix MUST be + returned in a single Map-Reply message. For instance, if an ETR had + database mapping entries for EID-Prefixes: + + 10.0.0.0/8 + 10.1.0.0/16 + 10.1.1.0/24 + 10.1.2.0/24 + + A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record + count of 1 to be returned with a mapping record EID-Prefix of + 10.1.1.0/24. + + A Map-Request for EID 10.1.5.5 would cause a Map-Reply with a record + count of 3 to be returned with mapping records for EID-Prefixes + 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. + + Note that not all overlapping EID-Prefixes need to be returned but + only the more-specific entries (note that in the second example above + 10.0.0.0/8 was not returned for requesting EID 10.1.5.5) for the + matching EID-Prefix of the requesting EID. When more than one + EID-Prefix is returned, all SHOULD use the same Time to Live value so + they can all time out at the same time. When a more-specific + EID-Prefix is received later, its Time to Live value in the Map-Reply + record can be stored even when other less-specific entries exist. + When a less-specific EID-Prefix is received later, its map-cache + expiration time SHOULD be set to the minimum expiration time of any + more-specific EID-Prefix in the map-cache. This is done so the + integrity of the EID-Prefix set is wholly maintained and so no more- + specific entries are removed from the map-cache while keeping less- + specific entries. + + Map-Replies SHOULD be sent for an EID-Prefix no more often than once + per second to the same requesting router. For scalability, it is + expected that aggregation of EID addresses into EID-Prefixes will + allow one Map-Reply to satisfy a mapping for the EID addresses in the + prefix range, thereby reducing the number of Map-Request messages. + + Map-Reply records can have an empty Locator-Set. A Negative + Map-Reply is a Map-Reply with an empty Locator-Set. Negative + Map-Replies convey special actions by the sender to the ITR or PITR + that have solicited the Map-Reply. There are two primary + applications for Negative Map-Replies. The first is for a + Map-Resolver to instruct an ITR or PITR when a destination is for a + LISP site versus a non-LISP site, and the other is to source quench + Map-Requests that are sent for non-allocated EIDs. + + + + +Farinacci, et al. Experimental [Page 36] + +RFC 6830 LISP January 2013 + + + For each Map-Reply record, the list of Locators in a Locator-Set MUST + appear in the same order for each ETR that originates a Map-Reply + message. The Locator-Set MUST be sorted in order of ascending IP + address where an IPv4 locator address is considered numerically 'less + than' an IPv6 locator address. + + When sending a Map-Reply message, the destination address is copied + from one of the 'ITR-RLOC' fields from the Map-Request. The ETR can + choose a locator address from one of the address families it + supports. For Data-Probes, the destination address of the Map-Reply + is copied from the source address of the Data-Probe message that is + invoking the reply. The source address of the Map-Reply is one of + the local IP addresses chosen to allow Unicast Reverse Path + Forwarding (uRPF) checks to succeed in the upstream service provider. + The destination port of a Map-Reply message is copied from the source + port of the Map-Request or Data-Probe, and the source port of the + Map-Reply message is set to the well-known UDP port 4342. + +6.1.5.1. Traffic Redirection with Coarse EID-Prefixes + + When an ETR is misconfigured or compromised, it could return coarse + EID-Prefixes in Map-Reply messages it sends. The EID-Prefix could + cover EID-Prefixes that are allocated to other sites, redirecting + their traffic to the Locators of the compromised site. + + To solve this problem, there are two basic solutions that could be + used. The first is to have Map-Servers proxy Map-Reply on behalf of + ETRs so their registered EID-Prefixes are the ones returned in + Map-Replies. Since the interaction between an ETR and Map-Server is + secured with shared keys, it is easier for an ETR to detect + misbehavior. The second solution is to have ITRs and PITRs cache + EID-Prefixes with mask lengths that are greater than or equal to a + configured prefix length. This limits the damage to a specific width + of any EID-Prefix advertised but needs to be coordinated with the + allocation of site prefixes. These solutions can be used + independently or at the same time. + + At the time of this writing, other approaches are being considered + and researched. + +6.1.6. Map-Register Message Format + + The usage details of the Map-Register message can be found in + specification [RFC6833]. This section solely defines the message + format. + + The message is sent in UDP with a destination UDP port of 4342 and a + randomly selected UDP source port number. + + + +Farinacci, et al. Experimental [Page 37] + +RFC 6830 LISP January 2013 + + + The Map-Register message format is: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Type=3 |P| Reserved |M| Record Count | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Nonce . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | . . . Nonce | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Key ID | Authentication Data Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ Authentication Data ~ + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Record TTL | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + R | Locator Count | EID mask-len | ACT |A| Reserved | + e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + c | Rsvd | Map-Version Number | EID-Prefix-AFI | + o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + r | EID-Prefix | + d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | /| Priority | Weight | M Priority | M Weight | + | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | o | Unused Flags |L|p|R| Loc-AFI | + | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | \| Locator | + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Packet field descriptions: + + Type: 3 (Map-Register) + + P: This is the proxy Map-Reply bit. When set to 1, an ETR sends a + Map-Register message requesting the Map-Server to proxy a + Map-Reply. The Map-Server will send non-authoritative Map-Replies + on behalf of the ETR. Details on this usage can be found in + [RFC6833]. + + Reserved: This field MUST be set to 0 on transmit and MUST be + ignored on receipt. + + M: This is the want-map-notify bit. When set to 1, an ETR is + requesting a Map-Notify message to be returned in response to + sending a Map-Register message. The Map-Notify message sent by a + Map-Server is used to acknowledge receipt of a Map-Register + message. + + + +Farinacci, et al. Experimental [Page 38] + +RFC 6830 LISP January 2013 + + + Record Count: This is the number of records in this Map-Register + message. A record is comprised of that portion of the packet + labeled 'Record' above and occurs the number of times equal to + Record Count. + + Nonce: This 8-octet 'Nonce' field is set to 0 in Map-Register + messages. Since the Map-Register message is authenticated, the + 'Nonce' field is not currently used for any security function but + may be in the future as part of an anti-replay solution. + + Key ID: This is a configured ID to find the configured Message + Authentication Code (MAC) algorithm and key value used for the + authentication function. See Section 14.4 for codepoint + assignments. + + Authentication Data Length: This is the length in octets of the + 'Authentication Data' field that follows this field. The length + of the 'Authentication Data' field is dependent on the MAC + algorithm used. The length field allows a device that doesn't + know the MAC algorithm to correctly parse the packet. + + Authentication Data: This is the message digest used from the output + of the MAC algorithm. The entire Map-Register payload is + authenticated with this field preset to 0. After the MAC is + computed, it is placed in this field. Implementations of this + specification MUST include support for HMAC-SHA-1-96 [RFC2404], + and support for HMAC-SHA-256-128 [RFC4868] is RECOMMENDED. + + The definition of the rest of the Map-Register can be found in + Section 6.1.4. + +6.1.7. Map-Notify Message Format + + The usage details of the Map-Notify message can be found in + specification [RFC6833]. This section solely defines the message + format. + + The message is sent inside a UDP packet with source and destination + UDP ports equal to 4342. + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 39] + +RFC 6830 LISP January 2013 + + + The Map-Notify message format is: + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + |Type=4 | Reserved | Record Count | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Nonce . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | . . . Nonce | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Key ID | Authentication Data Length | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ Authentication Data ~ + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | Record TTL | + | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + R | Locator Count | EID mask-len | ACT |A| Reserved | + e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + c | Rsvd | Map-Version Number | EID-Prefix-AFI | + o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + r | EID-Prefix | + d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | /| Priority | Weight | M Priority | M Weight | + | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | o | Unused Flags |L|p|R| Loc-AFI | + | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | \| Locator | + +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Packet field descriptions: + + Type: 4 (Map-Notify) + + The Map-Notify message has the same contents as a Map-Register + message. See the Map-Register section for field descriptions. + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 40] + +RFC 6830 LISP January 2013 + + +6.1.8. Encapsulated Control Message Format + + An Encapsulated Control Message (ECM) is used to encapsulate control + packets sent between xTRs and the mapping database system described + in [RFC6833]. + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | IPv4 or IPv6 Header | + OH | (uses RLOC addresses) | + \ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port = xxxx | Dest Port = 4342 | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + LH |Type=8 |S| Reserved | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | IPv4 or IPv6 Header | + IH | (uses RLOC or EID addresses) | + \ | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + / | Source Port = xxxx | Dest Port = yyyy | + UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + \ | UDP Length | UDP Checksum | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + LCM | LISP Control Message | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + Packet header descriptions: + + OH: The outer IPv4 or IPv6 header, which uses RLOC addresses in the + source and destination header address fields. + + UDP: The outer UDP header with destination port 4342. The source + port is randomly allocated. The checksum field MUST be + non-zero. + + LH: Type 8 is defined to be a "LISP Encapsulated Control Message", + and what follows is either an IPv4 or IPv6 header as encoded by + the first 4 bits after the 'Reserved' field. + + S: This is the Security bit. When set to 1, the field following + the 'Reserved' field will have the following format. The + detailed format of the Authentication Data Content is for + further study. + + + + +Farinacci, et al. Experimental [Page 41] + +RFC 6830 LISP January 2013 + + + 0 1 2 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | AD Type | Authentication Data Content . . . | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + IH: The inner IPv4 or IPv6 header, which can use either RLOC or EID + addresses in the header address fields. When a Map-Request is + encapsulated in this packet format, the destination address in + this header is an EID. + + UDP: The inner UDP header, where the port assignments depend on the + control packet being encapsulated. When the control packet is + a Map-Request or Map-Register, the source port is selected by + the ITR/PITR and the destination port is 4342. When the + control packet is a Map-Reply, the source port is 4342 and the + destination port is assigned from the source port of the + invoking Map-Request. Port number 4341 MUST NOT be assigned to + either port. The checksum field MUST be non-zero. + + LCM: The format is one of the control message formats described in + this section. At this time, only Map-Request messages are + allowed to be encapsulated. In the future, PIM Join/Prune + messages [RFC6831] might be allowed. Encapsulating other types + of LISP control messages is for further study. When + Map-Requests are sent for RLOC-Probing purposes (i.e., the + probe-bit is set), they MUST NOT be sent inside Encapsulated + Control Messages. + +6.2. Routing Locator Selection + + Both the client-side and server-side may need control over the + selection of RLOCs for conversations between them. This control is + achieved by manipulating the 'Priority' and 'Weight' fields in + EID-to-RLOC Map-Reply messages. Alternatively, RLOC information MAY + be gleaned from received tunneled packets or EID-to-RLOC Map-Request + messages. + + The following are different scenarios for choosing RLOCs and the + controls that are available: + + o The server-side returns one RLOC. The client-side can only use + one RLOC. The server-side has complete control of the selection. + + o The server-side returns a list of RLOCs where a subset of the list + has the same best Priority. The client can only use the subset + list according to the weighting assigned by the server-side. In + this case, the server-side controls both the subset list and + + + +Farinacci, et al. Experimental [Page 42] + +RFC 6830 LISP January 2013 + + + load-splitting across its members. The client-side can use RLOCs + outside of the subset list if it determines that the subset list + is unreachable (unless RLOCs are set to a Priority of 255). Some + sharing of control exists: the server-side determines the + destination RLOC list and load distribution while the client-side + has the option of using alternatives to this list if RLOCs in the + list are unreachable. + + o The server-side sets a Weight of 0 for the RLOC subset list. In + this case, the client-side can choose how the traffic load is + spread across the subset list. Control is shared by the server- + side determining the list and the client determining load + distribution. Again, the client can use alternative RLOCs if the + server-provided list of RLOCs is unreachable. + + o Either side (more likely the server-side ETR) decides not to send + a Map-Request. For example, if the server-side ETR does not send + Map-Requests, it gleans RLOCs from the client-side ITR, giving the + client-side ITR responsibility for bidirectional RLOC reachability + and preferability. Server-side ETR gleaning of the client-side + ITR RLOC is done by caching the inner-header source EID and the + outer-header source RLOC of received packets. The client-side ITR + controls how traffic is returned and can alternate using an outer- + header source RLOC, which then can be added to the list the + server-side ETR uses to return traffic. Since no Priority or + Weights are provided using this method, the server-side ETR MUST + assume that each client-side ITR RLOC uses the same best Priority + with a Weight of zero. In addition, since EID-Prefix encoding + cannot be conveyed in data packets, the EID-to-RLOC Cache on + Tunnel Routers can grow to be very large. + + o A "gleaned" Map-Cache entry, one learned from the source RLOC of a + received encapsulated packet, is only stored and used for a few + seconds, pending verification. Verification is performed by + sending a Map-Request to the source EID (the inner-header IP + source address) of the received encapsulated packet. A reply to + this "verifying Map-Request" is used to fully populate the + Map-Cache entry for the "gleaned" EID and is stored and used for + the time indicated from the 'TTL' field of a received Map-Reply. + When a verified Map-Cache entry is stored, data gleaning no longer + occurs for subsequent packets that have a source EID that matches + the EID-Prefix of the verified entry. + + RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be + reachable when the R-bit for the Locator record is set to 1. When + the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the + RLOC. Neither the information contained in a Map-Reply nor that + stored in the mapping database system provides reachability + + + +Farinacci, et al. Experimental [Page 43] + +RFC 6830 LISP January 2013 + + + information for RLOCs. Note that reachability is not part of the + mapping system and is determined using one or more of the Routing + Locator reachability algorithms described in the next section. + +6.3. Routing Locator Reachability + + Several mechanisms for determining RLOC reachability are currently + defined: + + 1. An ETR may examine the Locator-Status-Bits in the LISP header of + an encapsulated data packet received from an ITR. If the ETR is + also acting as an ITR and has traffic to return to the original + ITR site, it can use this status information to help select an + RLOC. + + 2. An ITR may receive an ICMP Network Unreachable or Host + Unreachable message for an RLOC it is using. This indicates that + the RLOC is likely down. Note that trusting ICMP messages may + not be desirable, but neither is ignoring them completely. + Implementations are encouraged to follow current best practices + in treating these conditions. + + 3. An ITR that participates in the global routing system can + determine that an RLOC is down if no BGP Routing Information Base + (RIB) route exists that matches the RLOC IP address. + + 4. An ITR may receive an ICMP Port Unreachable message from a + destination host. This occurs if an ITR attempts to use + interworking [RFC6832] and LISP-encapsulated data is sent to a + non-LISP-capable site. + + 5. An ITR may receive a Map-Reply from an ETR in response to a + previously sent Map-Request. The RLOC source of the Map-Reply is + likely up, since the ETR was able to send the Map-Reply to the + ITR. + + 6. When an ETR receives an encapsulated packet from an ITR, the + source RLOC from the outer header of the packet is likely up. + + 7. An ITR/ETR pair can use the Locator reachability algorithms + described in this section, namely Echo-Noncing or RLOC-Probing. + + + + + + + + + + +Farinacci, et al. Experimental [Page 44] + +RFC 6830 LISP January 2013 + + + When determining Locator up/down reachability by examining the + Locator-Status-Bits from the LISP-encapsulated data packet, an ETR + will receive up-to-date status from an encapsulating ITR about + reachability for all ETRs at the site. CE-based ITRs at the source + site can determine reachability relative to each other using the site + IGP as follows: + + o Under normal circumstances, each ITR will advertise a default + route into the site IGP. + + o If an ITR fails or if the upstream link to its PE fails, its + default route will either time out or be withdrawn. + + Each ITR can thus observe the presence or lack of a default route + originated by the others to determine the Locator-Status-Bits it sets + for them. + + RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The + Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 + to n-1 starting with the least significant bit. For example, if an + RLOC listed in the 3rd position of the Map-Reply goes down (ordinal + value 2), then all ITRs at the site will clear the 3rd least + significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for + the packets they encapsulate. + + When an ETR decapsulates a packet, it will check for any change in + the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the + ETR, if acting also as an ITR, will refrain from encapsulating + packets to an RLOC that is indicated as down. It will only resume + using that RLOC if the corresponding Locator-Status-Bit returns to a + value of 1. Locator-Status-Bits are associated with a Locator-Set + per EID-Prefix. Therefore, when a Locator becomes unreachable, the + Locator-Status-Bit that corresponds to that Locator's position in the + list returned by the last Map-Reply will be set to zero for that + particular EID-Prefix. + + When ITRs at the site are not deployed in CE routers, the IGP can + still be used to determine the reachability of Locators, provided + they are injected into the IGP. This is typically done when a /32 + address is configured on a loopback interface. + + When ITRs receive ICMP Network Unreachable or Host Unreachable + messages as a method to determine unreachability, they will refrain + from using Locators that are described in Locator lists of + Map-Replies. However, using this approach is unreliable because many + network operators turn off generation of ICMP Destination Unreachable + messages. + + + + +Farinacci, et al. Experimental [Page 45] + +RFC 6830 LISP January 2013 + + + If an ITR does receive an ICMP Network Unreachable or Host + Unreachable message, it MAY originate its own ICMP Destination + Unreachable message destined for the host that originated the data + packet the ITR encapsulated. + + Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a + locator address from a Locator-Set in a mapping entry matches a + prefix. If it does not find one and BGP is running in the Default- + Free Zone (DFZ), it can decide to not use the Locator even though the + Locator-Status-Bits indicate that the Locator is up. In this case, + the path from the ITR to the ETR that is assigned the Locator is not + available. More details are in [LOC-ID-ARCH]. + + Optionally, an ITR can send a Map-Request to a Locator, and if a + Map-Reply is returned, reachability of the Locator has been + determined. Obviously, sending such probes increases the number of + control messages originated by Tunnel Routers for active flows, so + Locators are assumed to be reachable when they are advertised. + + This assumption does create a dependency: Locator unreachability is + detected by the receipt of ICMP Host Unreachable messages. When a + Locator has been determined to be unreachable, it is not used for + active traffic; this is the same as if it were listed in a Map-Reply + with Priority 255. + + The ITR can test the reachability of the unreachable Locator by + sending periodic Requests. Both Requests and Replies MUST be rate- + limited. Locator reachability testing is never done with data + packets, since that increases the risk of packet loss for end-to-end + sessions. + + When an ETR decapsulates a packet, it knows that it is reachable from + the encapsulating ITR because that is how the packet arrived. In + most cases, the ETR can also reach the ITR but cannot assume this to + be true, due to the possibility of path asymmetry. In the presence + of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD + NOT use the lack of return traffic as an indication that the ETR is + unreachable. Instead, it MUST use an alternate mechanism to + determine reachability. + +6.3.1. Echo Nonce Algorithm + + When data flows bidirectionally between Locators from different + sites, a data-plane mechanism called "nonce echoing" can be used to + determine reachability between an ITR and ETR. When an ITR wants to + solicit a nonce echo, it sets the N- and E-bits and places a 24-bit + nonce [RFC4086] in the LISP header of the next encapsulated data + packet. + + + +Farinacci, et al. Experimental [Page 46] + +RFC 6830 LISP January 2013 + + + When this packet is received by the ETR, the encapsulated packet is + forwarded as normal. When the ETR next sends a data packet to the + ITR, it includes the nonce received earlier with the N-bit set and + E-bit cleared. The ITR sees this "echoed nonce" and knows that the + path to and from the ETR is up. + + The ITR will set the E-bit and N-bit for every packet it sends while + in the echo-nonce-request state. The time the ITR waits to process + the echoed nonce before it determines the path is unreachable is + variable and is a choice left for the implementation. + + If the ITR is receiving packets from the ETR but does not see the + nonce echoed while being in the echo-nonce-request state, then the + path to the ETR is unreachable. This decision may be overridden by + other Locator reachability algorithms. Once the ITR determines that + the path to the ETR is down, it can switch to another Locator for + that EID-Prefix. + + Note that "ITR" and "ETR" are relative terms here. Both devices MUST + be implementing both ITR and ETR functionality for the echo nonce + mechanism to operate. + + The ITR and ETR may both go into the echo-nonce-request state at the + same time. The number of packets sent or the time during which echo + nonce requests are sent is an implementation-specific setting. + However, when an ITR is in the echo-nonce-request state, it can echo + the ETR's nonce in the next set of packets that it encapsulates and + subsequently continue sending echo-nonce-request packets. + + This mechanism does not completely solve the forward path + reachability problem, as traffic may be unidirectional. That is, the + ETR receiving traffic at a site may not be the same device as an ITR + that transmits traffic from that site, or the site-to-site traffic is + unidirectional so there is no ITR returning traffic. + + The echo-nonce algorithm is bilateral. That is, if one side sets the + E-bit and the other side is not enabled for echo-noncing, then the + echoing of the nonce does not occur and the requesting side may + erroneously consider the Locator unreachable. An ITR SHOULD only set + the E-bit in an encapsulated data packet when it knows the ETR is + enabled for echo-noncing. This is conveyed by the E-bit in the + Map-Reply message. + + Note that other Locator reachability mechanisms are being researched + and can be used to compliment or even override the echo nonce + algorithm. See the next section for an example of control-plane + probing. + + + + +Farinacci, et al. Experimental [Page 47] + +RFC 6830 LISP January 2013 + + +6.3.2. RLOC-Probing Algorithm + + RLOC-Probing is a method that an ITR or PITR can use to determine the + reachability status of one or more Locators that it has cached in a + Map-Cache entry. The probe-bit of the Map-Request and Map-Reply + messages is used for RLOC-Probing. + + RLOC-Probing is done in the control plane on a timer basis, where an + ITR or PITR will originate a Map-Request destined to a locator + address from one of its own locator addresses. A Map-Request used as + an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or to + the mapping database system as one would when soliciting mapping + data. The EID record encoded in the Map-Request is the EID-Prefix of + the Map-Cache entry cached by the ITR or PITR. The ITR may include a + mapping data record for its own database mapping information that + contains the local EID-Prefixes and RLOCs for its site. RLOC-probes + are sent periodically using a jittered timer interval. + + When an ETR receives a Map-Request message with the probe-bit set, it + returns a Map-Reply with the probe-bit set. The source address of + the Map-Reply is set according to the procedure described in + Section 6.1.5. The Map-Reply SHOULD contain mapping data for the + EID-Prefix contained in the Map-Request. This provides the + opportunity for the ITR or PITR that sent the RLOC-probe to get + mapping updates if there were changes to the ETR's database mapping + entries. + + There are advantages and disadvantages of RLOC-Probing. The greatest + benefit of RLOC-Probing is that it can handle many failure scenarios + allowing the ITR to determine when the path to a specific Locator is + reachable or has become unreachable, thus providing a robust + mechanism for switching to using another Locator from the cached + Locator. RLOC-Probing can also provide rough Round-Trip Time (RTT) + estimates between a pair of Locators, which can be useful for network + management purposes as well as for selecting low delay paths. The + major disadvantage of RLOC-Probing is in the number of control + messages required and the amount of bandwidth used to obtain those + benefits, especially if the requirement for failure detection times + is very small. + + Continued research and testing will attempt to characterize the + tradeoffs of failure detection times versus message overhead. + + + + + + + + + +Farinacci, et al. Experimental [Page 48] + +RFC 6830 LISP January 2013 + + +6.4. EID Reachability within a LISP Site + + A site may be multihomed using two or more ETRs. The hosts and + infrastructure within a site will be addressed using one or more + EID-Prefixes that are mapped to the RLOCs of the relevant ETRs in the + mapping system. One possible failure mode is for an ETR to lose + reachability to one or more of the EID-Prefixes within its own site. + When this occurs when the ETR sends Map-Replies, it can clear the + R-bit associated with its own Locator. And when the ETR is also an + ITR, it can clear its Locator-Status-Bit in the encapsulation data + header. + + It is recognized that there are no simple solutions to the site + partitioning problem because it is hard to know which part of the + EID-Prefix range is partitioned and which Locators can reach any + sub-ranges of the EID-Prefixes. This problem is under investigation + with the expectation that experiments will tell us more. Note that + this is not a new problem introduced by the LISP architecture. The + problem exists today when a multihomed site uses BGP to advertise its + reachability upstream. + +6.5. Routing Locator Hashing + + When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to + a requesting ITR, the Locator-Set for the EID-Prefix may contain + different Priority values for each locator address. When more than + one best Priority Locator exists, the ITR can decide how to load- + share traffic against the corresponding Locators. + + The following hash algorithm may be used by an ITR to select a + Locator for a packet destined to an EID for the EID-to-RLOC mapping: + + 1. Either a source and destination address hash or the traditional + 5-tuple hash can be used. The traditional 5-tuple hash includes + the source and destination addresses; source and destination TCP, + UDP, or Stream Control Transmission Protocol (SCTP) port numbers; + and the IP protocol number field or IPv6 next-protocol fields of + a packet that a host originates from within a LISP site. When a + packet is not a TCP, UDP, or SCTP packet, the source and + destination addresses only from the header are used to compute + the hash. + + 2. Take the hash value and divide it by the number of Locators + stored in the Locator-Set for the EID-to-RLOC mapping. + + 3. The remainder will yield a value of 0 to "number of Locators + minus 1". Use the remainder to select the Locator in the + Locator-Set. + + + +Farinacci, et al. Experimental [Page 49] + +RFC 6830 LISP January 2013 + + + Note that when a packet is LISP encapsulated, the source port number + in the outer UDP header needs to be set. Selecting a hashed value + allows core routers that are attached to Link Aggregation Groups + (LAGs) to load-split the encapsulated packets across member links of + such LAGs. Otherwise, core routers would see a single flow, since + packets have a source address of the ITR, for packets that are + originated by different EIDs at the source site. A suggested setting + for the source port number computed by an ITR is a 5-tuple hash + function on the inner header, as described above. + + Many core router implementations use a 5-tuple hash to decide how to + balance packet load across members of a LAG. The 5-tuple hash + includes the source and destination addresses of the packet and the + source and destination ports when the protocol number in the packet + is TCP or UDP. For this reason, UDP encoding is used for LISP + encapsulation. + +6.6. Changing the Contents of EID-to-RLOC Mappings + + Since the LISP architecture uses a caching scheme to retrieve and + store EID-to-RLOC mappings, the only way an ITR can get a more up-to- + date mapping is to re-request the mapping. However, the ITRs do not + know when the mappings change, and the ETRs do not keep track of + which ITRs requested its mappings. For scalability reasons, we want + to maintain this approach but need to provide a way for ETRs to + change their mappings and inform the sites that are currently + communicating with the ETR site using such mappings. + + When adding a new Locator record in lexicographic order to the end of + a Locator-Set, it is easy to update mappings. We assume that new + mappings will maintain the same Locator ordering as the old mapping + but will just have new Locators appended to the end of the list. So, + some ITRs can have a new mapping while other ITRs have only an old + mapping that is used until they time out. When an ITR has only an + old mapping but detects bits set in the Locator-Status-Bits that + correspond to Locators beyond the list it has cached, it simply + ignores them. However, this can only happen for locator addresses + that are lexicographically greater than the locator addresses in the + existing Locator-Set. + + When a Locator record is inserted in the middle of a Locator-Set, to + maintain lexicographic order, the SMR procedure in Section 6.6.2 is + used to inform ITRs and PITRs of the new Locator-Status-Bit mappings. + + When a Locator record is removed from a Locator-Set, ITRs that have + the mapping cached will not use the removed Locator because the xTRs + will set the Locator-Status-Bit to 0. So, even if the Locator is in + the list, it will not be used. For new mapping requests, the xTRs + + + +Farinacci, et al. Experimental [Page 50] + +RFC 6830 LISP January 2013 + + + can set the Locator AFI to 0 (indicating an unspecified address), as + well as setting the corresponding Locator-Status-Bit to 0. This + forces ITRs with old or new mappings to avoid using the removed + Locator. + + If many changes occur to a mapping over a long period of time, one + will find empty record slots in the middle of the Locator-Set and new + records appended to the Locator-Set. At some point, it would be + useful to compact the Locator-Set so the Locator-Status-Bit settings + can be efficiently packed. + + We propose here three approaches for Locator-Set compaction: one + operational mechanism and two protocol mechanisms. The operational + approach uses a clock sweep method. The protocol approaches use the + concept of Solicit-Map-Requests and Map-Versioning. + +6.6.1. Clock Sweep + + The clock sweep approach uses planning in advance and the use of + count-down TTLs to time out mappings that have already been cached. + The default setting for an EID-to-RLOC mapping TTL is 24 hours. So, + there is a 24-hour window to time out old mappings. The following + clock sweep procedure is used: + + 1. 24 hours before a mapping change is to take effect, a network + administrator configures the ETRs at a site to start the clock + sweep window. + + 2. During the clock sweep window, ETRs continue to send Map-Reply + messages with the current (unchanged) mapping records. The TTL + for these mappings is set to 1 hour. + + 3. 24 hours later, all previous cache entries will have timed out, + and any active cache entries will time out within 1 hour. During + this 1-hour window, the ETRs continue to send Map-Reply messages + with the current (unchanged) mapping records with the TTL set to + 1 minute. + + 4. At the end of the 1-hour window, the ETRs will send Map-Reply + messages with the new (changed) mapping records. So, any active + caches can get the new mapping contents right away if not cached, + or in 1 minute if they had the mapping cached. The new mappings + are cached with a TTL equal to the TTL in the Map-Reply. + + + + + + + + +Farinacci, et al. Experimental [Page 51] + +RFC 6830 LISP January 2013 + + +6.6.2. Solicit-Map-Request (SMR) + + Soliciting a Map-Request is a selective way for ETRs, at the site + where mappings change, to control the rate they receive requests for + Map-Reply messages. SMRs are also used to tell remote ITRs to update + the mappings they have cached. + + Since the ETRs don't keep track of remote ITRs that have cached their + mappings, they do not know which ITRs need to have their mappings + updated. As a result, an ETR will solicit Map-Requests (called an + SMR message) from those sites to which it has been sending + encapsulated data for the last minute. In particular, an ETR will + send an SMR to an ITR to which it has recently sent encapsulated + data. + + An SMR message is simply a bit set in a Map-Request message. An ITR + or PITR will send a Map-Request when they receive an SMR message. + Both the SMR sender and the Map-Request responder MUST rate-limit + these messages. Rate-limiting can be implemented as a global rate- + limiter or one rate-limiter per SMR destination. + + The following procedure shows how an SMR exchange occurs when a site + is doing Locator-Set compaction for an EID-to-RLOC mapping: + + 1. When the database mappings in an ETR change, the ETRs at the site + begin to send Map-Requests with the SMR bit set for each Locator + in each Map-Cache entry the ETR caches. + + 2. A remote ITR that receives the SMR message will schedule sending + a Map-Request message to the source locator address of the SMR + message or to the mapping database system. A newly allocated + random nonce is selected, and the EID-Prefix used is the one + copied from the SMR message. If the source Locator is the only + Locator in the cached Locator-Set, the remote ITR SHOULD send a + Map-Request to the database mapping system just in case the + single Locator has changed and may no longer be reachable to + accept the Map-Request. + + 3. The remote ITR MUST rate-limit the Map-Request until it gets a + Map-Reply while continuing to use the cached mapping. When + Map-Versioning as described in Section 6.6.3 is used, an SMR + sender can detect if an ITR is using the most up-to-date database + mapping. + + 4. The ETRs at the site with the changed mapping will reply to the + Map-Request with a Map-Reply message that has a nonce from the + SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate- + limited. This is important to avoid Map-Reply implosion. + + + +Farinacci, et al. Experimental [Page 52] + +RFC 6830 LISP January 2013 + + + 5. The ETRs at the site with the changed mapping record the fact + that the site that sent the Map-Request has received the new + mapping data in the Map-Cache entry for the remote site so the + Locator-Status-Bits are reflective of the new mapping for packets + going to the remote site. The ETR then stops sending SMR + messages. + + Experimentation is in progress to determine the appropriate rate- + limit parameters. + + For security reasons, an ITR MUST NOT process unsolicited + Map-Replies. To avoid Map-Cache entry corruption by a third party, a + sender of an SMR-based Map-Request MUST be verified. If an ITR + receives an SMR-based Map-Request and the source is not in the + Locator-Set for the stored Map-Cache entry, then the responding + Map-Request MUST be sent with an EID destination to the mapping + database system. Since the mapping database system is a more secure + way to reach an authoritative ETR, it will deliver the Map-Request to + the authoritative source of the mapping data. + + When an ITR receives an SMR-based Map-Request for which it does not + have a cached mapping for the EID in the SMR message, it MAY not send + an SMR-invoked Map-Request. This scenario can occur when an ETR + sends SMR messages to all Locators in the Locator-Set it has stored + in its map-cache but the remote ITRs that receive the SMR may not be + sending packets to the site. There is no point in updating the ITRs + until they need to send, in which case they will send Map-Requests to + obtain a Map-Cache entry. + +6.6.3. Database Map-Versioning + + When there is unidirectional packet flow between an ITR and ETR, and + the EID-to-RLOC mappings change on the ETR, it needs to inform the + ITR so encapsulation to a removed Locator can stop and can instead be + started to a new Locator in the Locator-Set. + + An ETR, when it sends Map-Reply messages, conveys its own Map-Version + Number. This is known as the Destination Map-Version Number. ITRs + include the Destination Map-Version Number in packets they + encapsulate to the site. When an ETR decapsulates a packet and + detects that the Destination Map-Version Number is less than the + current version for its mapping, the SMR procedure described in + Section 6.6.2 occurs. + + + + + + + + +Farinacci, et al. Experimental [Page 53] + +RFC 6830 LISP January 2013 + + + An ITR, when it encapsulates packets to ETRs, can convey its own + Map-Version Number. This is known as the Source Map-Version Number. + When an ETR decapsulates a packet and detects that the Source + Map-Version Number is greater than the last Map-Version Number sent + in a Map-Reply from the ITR's site, the ETR will send a Map-Request + to one of the ETRs for the source site. + + A Map-Version Number is used as a sequence number per EID-Prefix, so + values that are greater are considered to be more recent. A value of + 0 for the Source Map-Version Number or the Destination Map-Version + Number conveys no versioning information, and an ITR does no + comparison with previously received Map-Version Numbers. + + A Map-Version Number can be included in Map-Register messages as + well. This is a good way for the Map-Server to assure that all ETRs + for a site registering to it will be synchronized according to + Map-Version Number. + + See [RFC6834] for a more detailed analysis and description of + Database Map-Versioning. + +7. Router Performance Considerations + + LISP is designed to be very "hardware-based forwarding friendly". A + few implementation techniques can be used to incrementally implement + LISP: + + o When a tunnel-encapsulated packet is received by an ETR, the outer + destination address may not be the address of the router. This + makes it challenging for the control plane to get packets from the + hardware. This may be mitigated by creating special Forwarding + Information Base (FIB) entries for the EID-Prefixes of EIDs served + by the ETR (those for which the router provides an RLOC + translation). These FIB entries are marked with a flag indicating + that control-plane processing should be performed. The forwarding + logic of testing for particular IP protocol number values is not + necessary. There are a few proven cases where no changes to + existing deployed hardware were needed to support the LISP data- + plane. + + o On an ITR, prepending a new IP header consists of adding more + octets to a MAC rewrite string and prepending the string as part + of the outgoing encapsulation procedure. Routers that support + Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 + tunneling [RFC3056] may already support this action. + + + + + + +Farinacci, et al. Experimental [Page 54] + +RFC 6830 LISP January 2013 + + + o A packet's source address or interface the packet was received on + can be used to select VRF (Virtual Routing/Forwarding). The VRF's + routing table can be used to find EID-to-RLOC mappings. + + For performance issues related to map-cache management, see + Section 12. + +8. Deployment Scenarios + + This section will explore how and where ITRs and ETRs can be deployed + and will discuss the pros and cons of each deployment scenario. For + a more detailed deployment recommendation, refer to [LISP-DEPLOY]. + + There are two basic deployment tradeoffs to consider: centralized + versus distributed caches; and flat, Recursive, or Re-encapsulating + Tunneling. When deciding on centralized versus distributed caching, + the following issues should be considered: + + o Are the Tunnel Routers spread out so that the caches are spread + across all the memories of each router? A centralized cache is + when an ITR keeps a cache for all the EIDs it is encapsulating to. + The packet takes a direct path to the destination Locator. A + distributed cache is when an ITR needs help from other + re-encapsulating routers because it does not store all the cache + entries for the EIDs it is encapsulating to. So, the packet takes + a path through re-encapsulating routers that have a different set + of cache entries. + + o Should management "touch points" be minimized by only choosing a + few Tunnel Routers, just enough for redundancy? + + o In general, using more ITRs doesn't increase management load, + since caches are built and stored dynamically. On the other hand, + using more ETRs does require more management, since EID-Prefix-to- + RLOC mappings need to be explicitly configured. + + When deciding on flat, Recursive, or Re-encapsulating Tunneling, the + following issues should be considered: + + o Flat tunneling implements a single tunnel between the source site + and destination site. This generally offers better paths between + sources and destinations with a single tunnel path. + + o Recursive Tunneling is when tunneled traffic is again further + encapsulated in another tunnel, either to implement VPNs or to + perform Traffic Engineering. When doing VPN-based tunneling, the + site has some control, since the site is prepending a new tunnel + header. In the case of TE-based tunneling, the site may have + + + +Farinacci, et al. Experimental [Page 55] + +RFC 6830 LISP January 2013 + + + control if it is prepending a new tunnel header, but if the site's + ISP is doing the TE, then the site has no control. Recursive + Tunneling generally will result in suboptimal paths but with the + benefit of steering traffic to parts of the network that have more + resources available. + + o The technique of re-encapsulation ensures that packets only + require one tunnel header. So, if a packet needs to be re-routed, + it is first decapsulated by the ETR and then re-encapsulated with + a new tunnel header using a new RLOC. + + The next sub-sections will examine where Tunnel Routers can reside in + the network. + +8.1. First-Hop/Last-Hop Tunnel Routers + + By locating Tunnel Routers close to hosts, the EID-Prefix set is at + the granularity of an IP subnet. So, at the expense of more + EID-Prefix-to-RLOC sets for the site, the caches in each Tunnel + Router can remain relatively small. But caches always depend on the + number of non-aggregated EID destination flows active through these + Tunnel Routers. + + With more Tunnel Routers doing encapsulation, the increase in control + traffic grows as well: since the EID granularity is greater, more + Map-Requests and Map-Replies are traveling between more routers. + + The advantage of placing the caches and databases at these stub + routers is that the products deployed in this part of the network + have better price-memory ratios than their core router counterparts. + Memory is typically less expensive in these devices, and fewer routes + are stored (only IGP routes). These devices tend to have excess + capacity, both for forwarding and routing states. + + LISP functionality can also be deployed in edge switches. These + devices generally have layer-2 ports facing hosts and layer-3 ports + facing the Internet. Spare capacity is also often available in these + devices. + +8.2. Border/Edge Tunnel Routers + + Using Customer Edge (CE) routers for tunnel endpoints allows the EID + space associated with a site to be reachable via a small set of RLOCs + assigned to the CE routers for that site. This is the default + behavior envisioned in the rest of this specification. + + + + + + +Farinacci, et al. Experimental [Page 56] + +RFC 6830 LISP January 2013 + + + This offers the opposite benefit of the first-hop/last-hop Tunnel + Router scenario: the number of mapping entries and network management + touch points is reduced, allowing better scaling. + + One disadvantage is that fewer network resources are used to reach + host endpoints, thereby centralizing the point-of-failure domain and + creating network choke points at the CE router. + + Note that more than one CE router at a site can be configured with + the same IP address. In this case, an RLOC is an anycast address. + This allows resilience between the CE routers. That is, if a CE + router fails, traffic is automatically routed to the other routers + using the same anycast address. However, this comes with the + disadvantage where the site cannot control the entrance point when + the anycast route is advertised out from all border routers. Another + disadvantage of using anycast Locators is the limited advertisement + scope of /32 (or /128 for IPv6) routes. + +8.3. ISP Provider Edge (PE) Tunnel Routers + + The use of ISP PE routers as tunnel endpoint routers is not the + typical deployment scenario envisioned in this specification. This + section attempts to capture some of the reasoning behind this + preference for implementing LISP on CE routers. + + The use of ISP PE routers as tunnel endpoint routers gives an ISP, + rather than a site, control over the location of the egress tunnel + endpoints. That is, the ISP can decide whether the tunnel endpoints + are in the destination site (in either CE routers or last-hop routers + within a site) or at other PE edges. The advantage of this case is + that two tunnel headers can be avoided. By having the PE be the + first router on the path to encapsulate, it can choose a TE path + first, and the ETR can decapsulate and re-encapsulate for a tunnel to + the destination end site. + + An obvious disadvantage is that the end site has no control over + where its packets flow or over the RLOCs used. Other disadvantages + include difficulty in synchronizing path liveness updates between CE + and PE routers. + + As mentioned in earlier sections, a combination of these scenarios is + possible at the expense of extra packet header overhead; if both site + and provider want control, then Recursive or Re-encapsulating Tunnels + are used. + + + + + + + +Farinacci, et al. Experimental [Page 57] + +RFC 6830 LISP January 2013 + + +8.4. LISP Functionality with Conventional NATs + + LISP routers can be deployed behind Network Address Translator (NAT) + devices to provide the same set of packet services hosts have today + when they are addressed out of private address space. + + It is important to note that a locator address in any LISP control + message MUST be a globally routable address and therefore SHOULD NOT + contain [RFC1918] addresses. If a LISP router is configured with + private addresses, they MUST be used only in the outer IP header so + the NAT device can translate properly. Otherwise, EID addresses MUST + be translated before encapsulation is performed. Both NAT + translation and LISP encapsulation functions could be co-located in + the same device. + + More details on LISP address translation can be found in [RFC6832]. + +8.5. Packets Egressing a LISP Site + + When a LISP site is using two ITRs for redundancy, the failure of one + ITR will likely shift outbound traffic to the second. This second + ITR's cache may not be populated with the same EID-to-RLOC mapping + entries as the first. If this second ITR does not have these + mappings, traffic will be dropped while the mappings are retrieved + from the mapping system. The retrieval of these messages may + increase the load of requests being sent into the mapping system. + Deployment and experimentation will determine whether this issue + requires more attention. + +9. Traceroute Considerations + + When a source host in a LISP site initiates a traceroute to a + destination host in another LISP site, it is highly desirable for it + to see the entire path. Since packets are encapsulated from the ITR + to the ETR, the hop across the tunnel could be viewed as a single + hop. However, LISP traceroute will provide the entire path so the + user can see 3 distinct segments of the path from a source LISP host + to a destination LISP host: + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 58] + +RFC 6830 LISP January 2013 + + + Segment 1 (in source LISP site based on EIDs): + + source host ---> first hop ... next hop ---> ITR + + Segment 2 (in the core network based on RLOCs): + + ITR ---> next hop ... next hop ---> ETR + + Segment 3 (in the destination LISP site based on EIDs): + + ETR ---> next hop ... last hop ---> destination host + + For segment 1 of the path, ICMP Time Exceeded messages are returned + in the normal manner as they are today. The ITR performs a TTL + decrement and tests for 0 before encapsulating. Therefore, the ITR's + hop is seen by the traceroute source as having an EID address (the + address of the site-facing interface). + + For segment 2 of the path, ICMP Time Exceeded messages are returned + to the ITR because the TTL decrement to 0 is done on the outer + header, so the destinations of the ICMP messages are the ITR RLOC + address and the source RLOC address of the encapsulated traceroute + packet. The ITR looks inside of the ICMP payload to inspect the + traceroute source so it can return the ICMP message to the address of + the traceroute client and also retain the core router IP address in + the ICMP message. This is so the traceroute client can display the + core router address (the RLOC address) in the traceroute output. The + ETR returns its RLOC address and responds to the TTL decrement to 0, + as the previous core routers did. + + For segment 3, the next-hop router downstream from the ETR will be + decrementing the TTL for the packet that was encapsulated, sent into + the core, decapsulated by the ETR, and forwarded because it isn't the + final destination. If the TTL is decremented to 0, any router on the + path to the destination of the traceroute, including the next-hop + router or destination, will send an ICMP Time Exceeded message to the + source EID of the traceroute client. The ICMP message will be + encapsulated by the local ITR and sent back to the ETR in the + originated traceroute source site, where the packet will be delivered + to the host. + +9.1. IPv6 Traceroute + + IPv6 traceroute follows the procedure described above, since the + entire traceroute data packet is included in the ICMP Time Exceeded + message payload. Therefore, only the ITR needs to pay special + attention to forwarding ICMP messages back to the traceroute source. + + + + +Farinacci, et al. Experimental [Page 59] + +RFC 6830 LISP January 2013 + + +9.2. IPv4 Traceroute + + For IPv4 traceroute, we cannot follow the above procedure, since IPv4 + ICMP Time Exceeded messages only include the invoking IP header and + 8 octets that follow the IP header. Therefore, when a core router + sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the + ICMP payload is the encapsulated header it prepended, followed by a + UDP header. The original invoking IP header, and therefore the + identity of the traceroute source, is lost. + + The solution we propose to solve this problem is to cache traceroute + IPv4 headers in the ITR and to match them up with corresponding IPv4 + Time Exceeded messages received from core routers and the ETR. The + ITR will use a circular buffer for caching the IPv4 and UDP headers + of traceroute packets. It will select a 16-bit number as a key to + find them later when the IPv4 Time Exceeded messages are received. + When an ITR encapsulates an IPv4 traceroute packet, it will use the + 16-bit number as the UDP source port in the encapsulating header. + When the ICMP Time Exceeded message is returned to the ITR, the UDP + header of the encapsulating header is present in the ICMP payload, + thereby allowing the ITR to find the cached headers for the + traceroute source. The ITR puts the cached headers in the payload + and sends the ICMP Time Exceeded message to the traceroute source + retaining the source address of the original ICMP Time Exceeded + message (a core router or the ETR of the site of the traceroute + destination). + + The signature of a traceroute packet comes in two forms. The first + form is encoded as a UDP message where the destination port is + inspected for a range of values. The second form is encoded as an + ICMP message where the IP identification field is inspected for a + well-known value. + +9.3. Traceroute Using Mixed Locators + + When either an IPv4 traceroute or IPv6 traceroute is originated and + the ITR encapsulates it in the other address family header, one + cannot get all 3 segments of the traceroute. Segment 2 of the + traceroute cannot be conveyed to the traceroute source, since it is + expecting addresses from intermediate hops in the same address format + for the type of traceroute it originated. Therefore, in this case, + segment 2 will make the tunnel look like one hop. All the ITR has to + do to make this work is to not copy the inner TTL to the outer, + encapsulating header's TTL when a traceroute packet is encapsulated + using an RLOC from a different address family. This will cause no + TTL decrement to 0 to occur in core routers between the ITR and ETR. + + + + + +Farinacci, et al. Experimental [Page 60] + +RFC 6830 LISP January 2013 + + +10. Mobility Considerations + + There are several kinds of mobility, of which only some might be of + concern to LISP. Essentially, they are as follows. + +10.1. Site Mobility + + A site wishes to change its attachment points to the Internet, and + its LISP Tunnel Routers will have new RLOCs when it changes upstream + providers. Changes in EID-to-RLOC mappings for sites are expected to + be handled by configuration, outside of LISP. + +10.2. Slow Endpoint Mobility + + An individual endpoint wishes to move but is not concerned about + maintaining session continuity. Renumbering is involved. LISP can + help with the issues surrounding renumbering [RFC4192] [LISA96] by + decoupling the address space used by a site from the address spaces + used by its ISPs [RFC4984]. + +10.3. Fast Endpoint Mobility + + Fast endpoint mobility occurs when an endpoint moves relatively + rapidly, changing its IP-layer network attachment point. Maintenance + of session continuity is a goal. This is where the Mobile IPv4 + [RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used and + primarily where interactions with LISP need to be explored. + + The problem is that as an endpoint moves, it may require changes to + the mapping between its EID and a set of RLOCs for its new network + location. When this is added to the overhead of Mobile IP binding + updates, some packets might be delayed or dropped. + + In IPv4 mobility, when an endpoint is away from home, packets to it + are encapsulated and forwarded via a home agent that resides in the + home area the endpoint's address belongs to. The home agent will + encapsulate and forward packets either directly to the endpoint or to + a foreign agent that resides where the endpoint has moved to. + Packets from the endpoint may be sent directly to the correspondent + node, may be sent via the foreign agent, or may be reverse-tunneled + back to the home agent for delivery to the mobile node. As the + mobile node's EID or available RLOC changes, LISP EID-to-RLOC + + + + + + + + + +Farinacci, et al. Experimental [Page 61] + +RFC 6830 LISP January 2013 + + + mappings are required for communication between the mobile node and + the home agent, whether via the foreign agent or not. As a mobile + endpoint changes networks, up to three LISP mapping changes may be + required: + + o The mobile node moves from an old location to a new visited + network location and notifies its home agent that it has done so. + The Mobile IPv4 control packets the mobile node sends pass through + one of the new visited network's ITRs, which needs an EID-to-RLOC + mapping for the home agent. + + o The home agent might not have the EID-to-RLOC mappings for the + mobile node's "care-of" address or its foreign agent in the new + visited network, in which case it will need to acquire them. + + o When packets are sent directly to the correspondent node, it may + be that no traffic has been sent from the new visited network to + the correspondent node's network, and the new visited network's + ITR will need to obtain an EID-to-RLOC mapping for the + correspondent node's site. + + In addition, if the IPv4 endpoint is sending packets from the new + visited network using its original EID, then LISP will need to + perform a route-returnability check on the new EID-to-RLOC mapping + for that EID. + + In IPv6 mobility, packets can flow directly between the mobile node + and the correspondent node in either direction. The mobile node uses + its "care-of" address (EID). In this case, the route-returnability + check would not be needed but one more LISP mapping lookup may be + required instead: + + o As above, three mapping changes may be needed for the mobile node + to communicate with its home agent and to send packets to the + correspondent node. + + o In addition, another mapping will be needed in the correspondent + node's ITR, in order for the correspondent node to send packets to + the mobile node's "care-of" address (EID) at the new network + location. + + When both endpoints are mobile, the number of potential mapping + lookups increases accordingly. + + As a mobile node moves, there are not only mobility state changes in + the mobile node, correspondent node, and home agent, but also state + changes in the ITRs and ETRs for at least some EID-Prefixes. + + + + +Farinacci, et al. Experimental [Page 62] + +RFC 6830 LISP January 2013 + + + The goal is to support rapid adaptation, with little delay or packet + loss for the entire system. Also, IP mobility can be modified to + require fewer mapping changes. In order to increase overall system + performance, there may be a need to reduce the optimization of one + area in order to place fewer demands on another. + + In LISP, one possibility is to "glean" information. When a packet + arrives, the ETR could examine the EID-to-RLOC mapping and use that + mapping for all outgoing traffic to that EID. It can do this after + performing a route-returnability check, to ensure that the new + network location does have an internal route to that endpoint. + However, this does not cover the case where an ITR (the node assigned + the RLOC) at the mobile-node location has been compromised. + + Mobile IP packet exchange is designed for an environment in which all + routing information is disseminated before packets can be forwarded. + In order to allow the Internet to grow to support expected future + use, we are moving to an environment where some information may have + to be obtained after packets are in flight. Modifications to IP + mobility should be considered in order to optimize the behavior of + the overall system. Anything that decreases the number of new + EID-to-RLOC mappings needed when a node moves, or maintains the + validity of an EID-to-RLOC mapping for a longer time, is useful. + +10.4. Fast Network Mobility + + In addition to endpoints, a network can be mobile, possibly changing + xTRs. A "network" can be as small as a single router and as large as + a whole site. This is different from site mobility in that it is + fast and possibly short-lived, but different from endpoint mobility + in that a whole prefix is changing RLOCs. However, the mechanisms + are the same, and there is no new overhead in LISP. A map request + for any endpoint will return a binding for the entire mobile prefix. + + If mobile networks become a more common occurrence, it may be useful + to revisit the design of the mapping service and allow for dynamic + updates of the database. + + The issue of interactions between mobility and LISP needs to be + explored further. Specific improvements to the entire system will + depend on the details of mapping mechanisms. Mapping mechanisms + should be evaluated on how well they support session continuity for + mobile nodes. + + + + + + + + +Farinacci, et al. Experimental [Page 63] + +RFC 6830 LISP January 2013 + + +10.5. LISP Mobile Node Mobility + + A mobile device can use the LISP infrastructure to achieve mobility + by implementing the LISP encapsulation and decapsulation functions + and acting as a simple ITR/ETR. By doing this, such a "LISP mobile + node" can use topologically independent EID IP addresses that are not + advertised into and do not impose a cost on the global routing + system. These EIDs are maintained at the edges of the mapping system + (in LISP Map-Servers and Map-Resolvers) and are provided on demand to + only the correspondents of the LISP mobile node. + + Refer to [LISP-MN] for more details. + +11. Multicast Considerations + + A multicast group address, as defined in the original Internet + architecture, is an identifier of a grouping of topologically + independent receiver host locations. The address encoding itself + does not determine the location of the receiver(s). The multicast + routing protocol, and the network-based state the protocol creates, + determine where the receivers are located. + + In the context of LISP, a multicast group address is both an EID and + a Routing Locator. Therefore, no specific semantic or action needs + to be taken for a destination address, as it would appear in an IP + header. Therefore, a group address that appears in an inner IP + header built by a source host will be used as the destination EID. + The outer IP header (the destination Routing Locator address), + prepended by a LISP router, will use the same group address as the + destination Routing Locator. + + Having said that, only the source EID and source Routing Locator need + to be dealt with. Therefore, an ITR merely needs to put its own IP + address in the source 'Routing Locator' field when prepending the + outer IP header. This source Routing Locator address, like any other + Routing Locator address, MUST be globally routable. + + Therefore, an EID-to-RLOC mapping does not need to be performed by an + ITR when a received data packet is a multicast data packet or when + processing a source-specific Join (either by IGMPv3 or PIM). But the + source Routing Locator is decided by the multicast routing protocol + in a receiver site. That is, an EID-to-RLOC translation is done at + control time. + + Another approach is to have the ITR not encapsulate a multicast + packet and allow the packet built by the host to flow into the core + even if the source address is allocated out of the EID namespace. If + the RPF-Vector TLV [RFC5496] is used by PIM in the core, then core + + + +Farinacci, et al. Experimental [Page 64] + +RFC 6830 LISP January 2013 + + + routers can RPF to the ITR (the locator address, which is injected + into core routing) rather than the host source address (the EID + address, which is not injected into core routing). + + To avoid any EID-based multicast state in the network core, the first + approach is chosen for LISP-Multicast. Details for LISP-Multicast + and interworking with non-LISP sites are described in [RFC6831] and + [RFC6832]. + +12. Security Considerations + + It is believed that most of the security mechanisms will be part of + the mapping database service when using control-plane procedures for + obtaining EID-to-RLOC mappings. For data-plane-triggered mappings, + as described in this specification, protection is provided against + ETR spoofing by using route-returnability (see Section 3) mechanisms + evidenced by the use of a 24-bit 'Nonce' field in the LISP + encapsulation header and a 64-bit 'Nonce' field in the LISP control + message. + + The nonce, coupled with the ITR accepting only solicited Map-Replies, + provides a basic level of security, in many ways similar to the + security experienced in the current Internet routing system. It is + hard for off-path attackers to launch attacks against these LISP + mechanisms, as they do not have the nonce values. Sending a large + number of packets to accidentally find the right nonce value is + possible but would already by itself be a denial-of-service (DoS) + attack. On-path attackers can perform far more serious attacks, but + on-path attackers can launch serious attacks in the current Internet + as well, including eavesdropping, blocking, or redirecting traffic. + See more discussion on this topic in Section 6.1.5.1. + + LISP does not rely on a PKI or a more heavyweight authentication + system. These systems challenge one of the primary design goals of + LISP -- scalability. + + DoS attack prevention will depend on implementations rate-limiting + Map-Requests and Map-Replies to the control plane as well as + rate-limiting the number of data-triggered Map-Replies. + + An incorrectly implemented or malicious ITR might choose to ignore + the Priority and Weights provided by the ETR in its Map-Reply. This + traffic-steering would be limited to the traffic that is sent by this + ITR's site and no more severe than if the site initiated a bandwidth + DoS attack on (one of) the ETR's ingress links. The ITR's site would + typically gain no benefit from not respecting the Weights and would + likely receive better service by abiding by them. + + + + +Farinacci, et al. Experimental [Page 65] + +RFC 6830 LISP January 2013 + + + To deal with map-cache exhaustion attempts in an ITR/PITR, the + implementation should consider putting a maximum cap on the number of + entries stored with a reserve list for special or frequently accessed + sites. This should be a configuration policy control set by the + network administrator who manages ITRs and PITRs. When overlapping + EID-Prefixes occur across multiple Map-Cache entries, the integrity + of the set must be wholly maintained. So, if a more-specific entry + cannot be added due to reaching the maximum cap, then none of the + less-specific entries should be stored in the map-cache. + + Given that the ITR/PITR maintains a cache of EID-to-RLOC mappings, + cache sizing and maintenance are issues to be kept in mind during + implementation. It is a good idea to have instrumentation in place + to detect thrashing of the cache. Implementation experimentation + will be used to determine which cache management strategies work + best. In general, it is difficult to defend against cache-thrashing + attacks. It should be noted that an undersized cache in an ITR/PITR + not only causes adverse effects on the site or region it supports but + may also cause increased Map-Request loads on the mapping system. + + "Piggybacked" mapping data as discussed in Section 6.1.3 specifies + how to handle such mappings and includes the possibility for an ETR + to temporarily accept such a mapping before verification when running + in "trusted" environments. In such cases, there is a potential + threat that a fake mapping could be inserted (even if only for a + short period) into a map-cache. As noted in Section 6.1.3, an ETR + MUST be specifically configured to run in such a mode and might + usefully only consider some specific ITRs as also running in that + same trusted environment. + + There is a security risk implicit in the fact that ETRs generate the + EID-Prefix to which they are responding. An ETR can claim a shorter + prefix than it is actually responsible for. Various mechanisms to + ameliorate or resolve this issue will be examined in the future + [LISP-SEC]. + + Spoofing of inner-header addresses of LISP-encapsulated packets is + possible, as with any tunneling mechanism. ITRs MUST verify the + source address of a packet to be an EID that belongs to the site's + EID-Prefix range prior to encapsulation. An ETR must only + decapsulate and forward datagrams with an inner-header destination + that matches one of its EID-Prefix ranges. If, upon receipt and + decapsulation, the destination EID of a datagram does not match one + of the ETR's configured EID-Prefixes, the ETR MUST drop the datagram. + If a LISP-encapsulated packet arrives at an ETR, it SHOULD compare + the inner-header source EID address and the outer-header source RLOC + address with the mapping that exists in the mapping database. Then, + + + + +Farinacci, et al. Experimental [Page 66] + +RFC 6830 LISP January 2013 + + + when spoofing attacks occur, the outer-header source RLOC address can + be used to trace back the attack to the source site, using existing + operational tools. + + This experimental specification does not address automated key + management (AKM). BCP 107 [RFC4107] provides guidance in this area. + In addition, at the time of this writing, substantial work is being + undertaken to improve security of the routing system [RFC6518] + [RFC6480] [BGP-SEC] [LISP-SEC]. Future work on LISP should address + the issues discussed in BCP 107 as well as other open security + considerations, which may require changes to this specification. + +13. Network Management Considerations + + Considerations for network management tools exist so the LISP + protocol suite can be operationally managed. These mechanisms can be + found in [LISP-MIB] and [RFC6835]. + +14. IANA Considerations + + This section provides guidance to the Internet Assigned Numbers + Authority (IANA) regarding registration of values related to the LISP + specification, in accordance with BCP 26 [RFC5226]. + + There are four namespaces (listed in the sub-sections below) in LISP + that have been registered. + + o LISP IANA registry allocations should not be made for purposes + unrelated to LISP routing or transport protocols. + + o The following policies are used here with the meanings defined in + BCP 26: "Specification Required", "IETF Review", "Experimental + Use", and "First Come First Served". + +14.1. LISP ACT and Flag Fields + + New ACT values (Section 6.1.4) can be allocated through IETF review + or IESG approval. Four values have already been allocated by this + specification (Section 6.1.4). + + In addition, LISP has a number of flag fields and reserved fields, + such as the LISP header flags field (Section 5.3). New bits for + flags in these fields can be implemented after IETF review or IESG + approval, but these need not be managed by IANA. + + + + + + + +Farinacci, et al. Experimental [Page 67] + +RFC 6830 LISP January 2013 + + +14.2. LISP Address Type Codes + + LISP Address [LCAF] type codes have a range from 0 to 255. New type + codes MUST be allocated consecutively, starting at 0. Type Codes + 0-127 are to be assigned by IETF review or IESG approval. + + Type Codes 128-255 are available according to the [RFC5226] First + Come First Served policy. + + This registry, initially empty, is constructed for future use in + experimental work related to LISP Canonical Address Format (LCAF) + values. See [LCAF] for details of other possible unapproved address + encodings. The unapproved LCAF encodings are an area for further + study and experimentation. + +14.3. LISP UDP Port Numbers + + The IANA registry has allocated UDP port numbers 4341 and 4342 for + lisp-data and lisp-control operation, respectively. IANA has updated + the description for UDP ports 4341 and 4342 as follows: + + lisp-data 4341 udp LISP Data Packets + lisp-control 4342 udp LISP Control Packets + +14.4. LISP Key ID Numbers + + The following Key ID values are defined by this specification as used + in any packet type that references a 'Key ID' field: + + Name Number Defined in + ----------------------------------------------- + None 0 n/a + HMAC-SHA-1-96 1 [RFC2404] + HMAC-SHA-256-128 2 [RFC4868] + + Number values are in the range of 0 to 65535. The allocation of + values is on a first come first served basis. + +15. Known Open Issues and Areas of Future Work + + As an experimental specification, this work is, by definition, + incomplete. Specific areas where additional experience and work are + needed include the following: + + o At present, only [RFC6836] is defined for implementing a database + of EID-to-RLOC mapping information. Additional research on other + mapping database systems is strongly encouraged. + + + + +Farinacci, et al. Experimental [Page 68] + +RFC 6830 LISP January 2013 + + + o Failure and recovery of LISP site partitioning (see Section 6.4) + in the presence of redundant configuration (see Section 8.5) needs + further research and experimentation. + + o The characteristics of map-cache management under exceptional + conditions, such as denial-of-service attacks, are not fully + understood. Further experience is needed to determine whether + current caching methods are practical or in need of further + development. In particular, the performance, scaling, and + security characteristics of the map-cache will be discovered as + part of this experiment. Performance metrics to be observed are + packet reordering associated with the LISP Data-Probe and loss of + the first packet in a flow associated with map-caching. The + impact of these upon TCP will be observed. See Section 12 for + additional thoughts and considerations. + + o Preliminary work has been done to ensure that sites employing LISP + can interconnect with the rest of the Internet. This work is + documented in [RFC6832], but further experimentation and + experience are needed. + + o At present, no mechanism for automated key management for message + authentication is defined. Addressing automated key management is + necessary before this specification can be developed into a + Standards Track RFC. See Section 12 for further details regarding + security considerations. + + o In order to maintain security and stability, Internet protocols + typically isolate the control and data planes. Therefore, user + activity cannot cause control-plane state to be created or + destroyed. LISP does not maintain this separation. The degree to + which the loss of separation impacts security and stability is a + topic for experimental observation. + + o LISP allows for the use of different mapping database systems. + While only one [RFC6836] is currently well defined, each mapping + database will likely have some impact on the security of the + EID-to-RLOC mappings. How each mapping database system's security + properties impact LISP overall is for further study. + + o An examination of the implications of LISP on Internet traffic, + applications, routers, and security is needed. This will help + implementors understand the consequences for network stability, + routing protocol function, routing scalability, migration and + backward compatibility, and implementation scalability (as + influenced by additional protocol components; additional state; + and additional processing for encapsulation, decapsulation, and + liveness). + + + +Farinacci, et al. Experimental [Page 69] + +RFC 6830 LISP January 2013 + + + o Experiments need to verify that LISP produces no significant + change in the behavior of protocols run between end-systems over a + LISP infrastructure versus being run directly between those same + end-systems. + + o Experiments need to verify that the issues raised in the Critique + section of [RFC6115] are either insignificant or have been + addressed by updates to LISP. + + Other LISP documents may also include open issues and areas for + future work. + +16. References + +16.1. Normative References + + [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, + August 1980. + + [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, + September 1981. + + [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and + E. Lear, "Address Allocation for Private Internets", + BCP 5, RFC 1918, February 1996. + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within + ESP and AH", RFC 2404, November 1998. + + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, December 1998. + + [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition + of Explicit Congestion Notification (ECN) to IP", + RFC 3168, September 2001. + + [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by + an On-line Database", RFC 3232, January 2002. + + [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness + Requirements for Security", BCP 106, RFC 4086, June 2005. + + [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing + (CIDR): The Internet Address Assignment and Aggregation + Plan", BCP 122, RFC 4632, August 2006. + + + +Farinacci, et al. Experimental [Page 70] + +RFC 6830 LISP January 2013 + + + [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, + HMAC-SHA-384, and HMAC-SHA-512 with IPsec", RFC 4868, + May 2007. + + [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an + IANA Considerations Section in RFCs", BCP 26, RFC 5226, + May 2008. + + [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path + Forwarding (RPF) Vector TLV", RFC 5496, March 2009. + + [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", + RFC 5944, November 2010. + + [RFC6115] Li, T., "Recommendation for a Routing Architecture", + RFC 6115, February 2011. + + [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support + in IPv6", RFC 6275, July 2011. + + [RFC6833] Farinacci, D. and V. Fuller, "Locator/ID Separation + Protocol (LISP) Map-Server Interface", RFC 6833, + January 2013. + + [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID + Separation Protocol (LISP) Map-Versioning", RFC 6834, + January 2013. + + [RFC6836] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, + "Locator/ID Separation Protocol Alternative Logical + Topology (LISP+ALT)", RFC 6836, January 2013. + +16.2. Informative References + + [AFI] IANA, "Address Family Numbers", + <http://www.iana.org/assignments/address-family-numbers>. + + [BGP-SEC] Lepinski, M. and S. Turner, "An Overview of BGPSEC", Work + in Progress, May 2012. + + [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed + Enhancement to the Internet Architecture", 1999, + <http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt>. + + [CONS] Brim, S., Chiappa, N., Farinacci, D., Fuller, V., Lewis, + D., and D. Meyer, "LISP-CONS: A Content distribution + Overlay Network Service for LISP", Work in Progress, + April 2008. + + + +Farinacci, et al. Experimental [Page 71] + +RFC 6830 LISP January 2013 + + + [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID + Mappings Multicast Across Cooperating Systems for LISP", + Work in Progress, November 2007. + + [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical + Address Format (LCAF)", Work in Progress, January 2013. + + [LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin, + "Renumbering: Threat or Menace?", Usenix Tenth System + Administration Conference (LISA 96), October 1996. + + [LISP-DEPLOY] + Jakab, L., Cabellos-Aparicio, A., Coras, F., + Domingo-Pascual, J., and D. Lewis, "LISP Network Element + Deployment Considerations", Work in Progress, + October 2012. + + [LISP-MIB] Schudel, G., Jain, A., and V. Moreno, "LISP MIB", Work + in Progress, January 2013. + + [LISP-MN] Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP + Mobile Node", Work in Progress, October 2012. + + [LISP-SEC] Maino, F., Ermagan, V., Cabellos, A., Saucez, D., and O. + Bonaventure, "LISP-Security (LISP-SEC)", Work in Progress, + October 2012. + + [LOC-ID-ARCH] + Meyer, D. and D. Lewis, "Architectural Implications of + Locator/ID Separation", Work in Progress, January 2009. + + [OPENLISP] Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP + Implementation Report", Work in Progress, July 2008. + + [RADIR] Narten, T., "On the Scalability of Internet Routing", Work + in Progress, February 2010. + + [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", + STD 13, RFC 1034, November 1987. + + [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. + Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, + March 2000. + + [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains + via IPv4 Clouds", RFC 3056, February 2001. + + + + + +Farinacci, et al. Experimental [Page 72] + +RFC 6830 LISP January 2013 + + + [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, + A., Peterson, J., Sparks, R., Handley, M., and E. + Schooler, "SIP: Session Initiation Protocol", RFC 3261, + June 2002. + + [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic + Key Management", BCP 107, RFC 4107, June 2005. + + [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for + Renumbering an IPv6 Network without a Flag Day", RFC 4192, + September 2005. + + [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route + Optimization for Mobile IPv6", RFC 4866, May 2007. + + [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB + Workshop on Routing and Addressing", RFC 4984, + September 2007. + + [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support + Secure Internet Routing", RFC 6480, February 2012. + + [RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for + Routing Protocols (KARP) Design Guidelines", RFC 6518, + February 2012. + + [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The + Locator/ID Separation Protocol (LISP) for Multicast + Environments", RFC 6831, January 2013. + + [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, + "Interworking between Locator/ID Separation Protocol + (LISP) and Non-LISP Sites", RFC 6832, January 2013. + + [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation + Protocol Internet Groper (LIG)", RFC 6835, January 2013. + + [RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to + Routing Locator (RLOC) Database", RFC 6837, January 2013. + + [UDP-TUNNELS] + Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and + UDP Checksums for Tunneled Packets", Work in Progress, + January 2013. + + [UDP-ZERO] Fairhurst, G. and M. Westerlund, "Applicability Statement + for the use of IPv6 UDP Datagrams with Zero Checksums", + Work in Progress, December 2012. + + + +Farinacci, et al. Experimental [Page 73] + +RFC 6830 LISP January 2013 + + +Appendix A. Acknowledgments + + An initial thank you goes to Dave Oran for planting the seeds for the + initial ideas for LISP. His consultation continues to provide value + to the LISP authors. + + A special and appreciative thank you goes to Noel Chiappa for + providing architectural impetus over the past decades on separation + of location and identity, as well as detailed reviews of the LISP + architecture and documents, coupled with enthusiasm for making LISP a + practical and incremental transition for the Internet. + + The authors would like to gratefully acknowledge many people who have + contributed discussions and ideas to the making of this proposal. + They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, + Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, + David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, + Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, + Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi + Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry + Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van + Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien + Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David + Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, + Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari + Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, + Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri + Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina + Ermagan, Albert Cabellos, Fabio Maino, Victor Moreno, Chris White, + Clarence Filsfils, and Alia Atlas. + + This work originated in the Routing Research Group (RRG) of the IRTF. + An individual submission was converted into the IETF LISP working + group document that became this RFC. + + The LISP working group would like to give a special thanks to Jari + Arkko, the Internet Area AD at the time that the set of LISP + documents were being prepared for IESG last call, and for his + meticulous reviews and detailed commentaries on the 7 working group + last call documents progressing toward experimental RFCs. + + + + + + + + + + + +Farinacci, et al. Experimental [Page 74] + +RFC 6830 LISP January 2013 + + +Authors' Addresses + + Dino Farinacci + Cisco Systems + Tasman Drive + San Jose, CA 95134 + USA + + EMail: farinacci@gmail.com + + + Vince Fuller + + EMail: vaf@vaf.net + + + Dave Meyer + Cisco Systems + 170 Tasman Drive + San Jose, CA + USA + + EMail: dmm@1-4-5.net + + + Darrel Lewis + Cisco Systems + 170 Tasman Drive + San Jose, CA + USA + + EMail: darlewis@cisco.com + + + + + + + + + + + + + + + + + + + +Farinacci, et al. Experimental [Page 75] + |