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diff --git a/doc/rfc/rfc7881.txt b/doc/rfc/rfc7881.txt new file mode 100644 index 0000000..ae17a15 --- /dev/null +++ b/doc/rfc/rfc7881.txt @@ -0,0 +1,451 @@ + + + + + + +Internet Engineering Task Force (IETF) C. Pignataro +Request for Comments: 7881 D. Ward +Category: Standards Track Cisco +ISSN: 2070-1721 N. Akiya + Big Switch Networks + July 2016 + + + Seamless Bidirectional Forwarding Detection (S-BFD) + for IPv4, IPv6, and MPLS + +Abstract + + This document defines procedures for using Seamless Bidirectional + Forwarding Detection (S-BFD) in IPv4, IPv6, and MPLS environments. + +Status of This Memo + + This is an Internet Standards Track document. + + 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). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + 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/rfc7881. + +Copyright Notice + + Copyright (c) 2016 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. + + + + + + + +Pignataro, et al. Standards Track [Page 1] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + +Table of Contents + + 1. Introduction ....................................................2 + 2. S-BFD UDP Port ..................................................2 + 3. S-BFD Echo UDP Port .............................................3 + 4. S-BFD Control Packet Demultiplexing .............................3 + 5. Initiator Procedures ............................................3 + 5.1. Details of S-BFD Control Packets Sent by SBFDInitiator .....4 + 5.1.1. Target versus Remote Entity (S-BFD Discriminator) ...4 + 6. Responder Procedures ............................................5 + 6.1. Details of S-BFD Control Packets Sent by SBFDReflector .....5 + 7. Security Considerations .........................................6 + 8. IANA Considerations .............................................6 + 9. References ......................................................7 + 9.1. Normative References .......................................7 + 9.2. Informative References .....................................7 + Acknowledgements ...................................................8 + Contributors .......................................................8 + Authors' Addresses .................................................8 + +1. Introduction + + Seamless Bidirectional Forwarding Detection (S-BFD) [RFC7880] defines + a generalized mechanism to allow network nodes to seamlessly perform + continuity checks to remote entities. This document defines + necessary procedures for using S-BFD in IPv4, IPv6, and MPLS + environments. + + The reader is expected to be familiar with the IP [RFC791] [RFC2460], + BFD [RFC5880], MPLS BFD [RFC5884], and S-BFD [RFC7880] terms and + protocol constructs. + + 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 RFC 2119 [RFC2119]. + +2. S-BFD UDP Port + + A new UDP port is defined for use by S-BFD in IPv4, IPv6, and MPLS + environments: 7784. + + In S-BFD Control packets from the SBFDInitiator to the SBFDReflector, + the SBFDReflector session MUST listen for incoming S-BFD Control + packets on port 7784. SBFDInitiator sessions MUST transmit S-BFD + Control packets with destination port 7784. The source port of the + S-BFD Control packets transmitted by SBFDInitiator sessions can be + any port, with one exception: it MUST NOT be 7784. The same UDP + + + + +Pignataro, et al. Standards Track [Page 2] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + + source port number MUST be used for all S-BFD Control packets + associated with a particular SBFDInitiator session. The source port + number is unique among all SBFDInitiator sessions on the system. + + In S-BFD Control packets from the SBFDReflector to the SBFDInitiator, + the SBFDInitiator session MUST listen for reflected S-BFD Control + packets at its source port. + +3. S-BFD Echo UDP Port + + The BFD Echo port defined by [RFC5881], port 3785, is used for the + S-BFD Echo function in IPv4, IPv6, and MPLS environments. + SBFDInitiator sessions MUST transmit S-BFD Echo packets with + destination port 3785. The setting of the UDP source port [RFC5881] + and the procedures [RFC7880] for the S-BFD Echo function are outside + the scope of this document. + +4. S-BFD Control Packet Demultiplexing + + S-BFD Control packet demultiplexing follows the procedure specified + in Section 7.1 of [RFC7880]. A received S-BFD Control packet MUST be + demultiplexed with the destination UDP port field. + + This procedure for an S-BFD packet is executed on both the initiator + and the reflector. If the port is 7784 (i.e., an S-BFD packet for + the SBFDReflector), then the packet MUST be looked up to locate a + corresponding SBFDReflector session based on the value from the + Your Discriminator field in the table describing S-BFD + Discriminators. If the port is not 7784 but the packet is + demultiplexed to be for an SBFDInitiator, then the packet MUST be + looked up to locate a corresponding SBFDInitiator session based on + the value from the Your Discriminator field in the table describing + BFD Discriminators. In that case, the destination IP address of the + packet SHOULD be validated to be for itself. If the packet + demultiplexes to a classical BFD session, then the procedures from + [RFC5880] apply. + +5. Initiator Procedures + + S-BFD Control packets are transmitted with an IP header, UDP header, + and BFD Control packet ([RFC5880]). When S-BFD Control packets are + explicitly label switched (i.e., not IP routed and forwarded over a + Label Switched Path (LSP), but explicitly sent on a specific LSP), + the former is prepended with a label stack. Note that this document + does not make a distinction between a single-hop S-BFD scenario and a + multi-hop S-BFD scenario; both scenarios are supported. + + + + + +Pignataro, et al. Standards Track [Page 3] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + + The necessary values in the BFD control headers are described in + [RFC7880]. Section 5.1 describes necessary values in the MPLS + header, IP header, and UDP header when an SBFDInitiator on the + initiator is sending S-BFD Control packets. + +5.1. Details of S-BFD Control Packets Sent by SBFDInitiator + + o Specifications common to both IP-routed S-BFD Control packets and + explicitly label-switched S-BFD Control packets: + + * The Source IP Address field of the IP header MUST be set to a + local IP address that is expected to be routable by the target + (i.e., not an IPv6 link-local address when the target is + multiple hops away). + + * The UDP destination port MUST be set to a well-known UDP + destination port assigned for S-BFD, i.e., 7784. + + * The UDP source port MUST NOT be set to 7784. + + o Specifications for IP-routed S-BFD Control packets: + + * The Destination IP Address field of the IP header MUST be set + to an IP address of the target. + + * The TTL / Hop Limit field of the IP header SHOULD be set + to 255. + + o Specifications for explicitly label-switched S-BFD Control + packets: + + * S-BFD Control packets MUST have the label stack that is + expected to reach the target. + + * The TTL field of the topmost label SHOULD be 255. + + * The destination IP address MUST be chosen from the 127/8 range + for IPv4 and from the 0:0:0:0:0:ffff:7f00:0/104 range for IPv6, + as per [RFC5884]. + + * The TTL / Hop Limit field of the IP header MUST be set to 1. + +5.1.1. Target versus Remote Entity (S-BFD Discriminator) + + Typically, an S-BFD Control packet will have the Your Discriminator + field corresponding to an S-BFD Discriminator of the remote entity + located on the target network node defined by the destination IP + address or the label stack. It is, however, possible for an + + + +Pignataro, et al. Standards Track [Page 4] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + + SBFDInitiator to carefully set the Your Discriminator and TTL fields + to perform a continuity test in the direction towards a target, but + destined to a transit network node and not to the target itself. + + Section 5.1 intentionally uses the word "target" instead of "remote + entity" to accommodate this possible S-BFD usage through TTL expiry. + This also requires that S-BFD Control packets not be dropped by the + responder node due to TTL expiry. Thus, implementations on the + responder MUST allow received S-BFD Control packets taking a TTL + expiry exception path to reach the corresponding SBFDReflector + session. This is an existing packet-processing exception practice + for Operations, Administration, and Maintenance (OAM) packets, where + the control plane further identifies the type of OAM by the protocol + and port numbers. + +6. Responder Procedures + + S-BFD Control packets are IP routed back to the initiator and will + have an IP header, UDP header, and BFD control header. If an + SBFDReflector receives an S-BFD Control packet with a UDP source port + of 7784, the packet MUST be discarded. Necessary values in the BFD + control header are described in [RFC7880]. Section 6.1 describes + necessary values in the IP header and UDP header when an + SBFDReflector on the responder is sending S-BFD Control packets. + +6.1. Details of S-BFD Control Packets Sent by SBFDReflector + + o The Destination IP Address field of the IP header MUST be copied + from the Source IP Address field of the received S-BFD Control + packet. + + o The Source IP Address field of the IP header MUST be set to a + local IP address that the initiator expects to be visible (i.e., + not an IPv6 link-local address when the initiator is multiple hops + away). The source IP address SHOULD be copied from the + Destination IP Address field of the received S-BFD Control packet, + except when it is from the 127/8 range for IPv4 or from the + 0:0:0:0:0:ffff:7f00:0/104 range for IPv6. + + o The TTL / Hop Limit field of the IP header MUST be set to 255. + + o The UDP destination port MUST be copied from the received UDP + source port. + + o The UDP source port MUST be copied from the received UDP + destination port. + + + + + +Pignataro, et al. Standards Track [Page 5] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + +7. Security Considerations + + Security considerations for S-BFD are discussed in [RFC7880]. + Additionally, implementing the following measures will strengthen + security aspects of the mechanism described by this document: + + o Implementations MUST provide filtering capability based on source + IP addresses of received S-BFD Control packets; see [RFC2827]. + + o Implementations MUST NOT act on received S-BFD Control packets + containing source Martian IP addresses (i.e., addresses that, by + application of the current forwarding tables, would not have their + return traffic routed back to the sender). + + o Implementations MUST ensure that response S-BFD Control packets + generated by the SBFDReflector and sent to the initiator have a + reachable target (e.g., destination IP address). + +8. IANA Considerations + + A new port number value, 7784, was allocated from the "Service Name + and Transport Protocol Port Number Registry". The allocated registry + entry is: + + Service Name (REQUIRED) + s-bfd + + Transport Protocol(s) (REQUIRED) + udp + + Assignee (REQUIRED) + IESG <iesg@ietf.org> + + Contact (REQUIRED) + IETF Chair <chair@ietf.org> + + Description (REQUIRED) + Seamless Bidirectional Forwarding Detection (S-BFD) + + Reference (REQUIRED) + RFC 7881 + + Port Number (OPTIONAL) + 7784 + + + + + + + +Pignataro, et al. Standards Track [Page 6] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + +9. References + +9.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <http://www.rfc-editor.org/info/rfc2119>. + + [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection + (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, + <http://www.rfc-editor.org/info/rfc5880>. + + [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection + (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, + DOI 10.17487/RFC5881, June 2010, + <http://www.rfc-editor.org/info/rfc5881>. + + [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. + Pallagatti, "Seamless Bidirectional Forwarding Detection + (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016, + <http://www.rfc-editor.org/info/rfc7880>. + +9.2. Informative References + + [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, + DOI 10.17487/RFC791, September 1981, + <http://www.rfc-editor.org/info/rfc791>. + + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, + December 1998, <http://www.rfc-editor.org/info/rfc2460>. + + [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: + Defeating Denial of Service Attacks which employ IP Source + Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, + May 2000, <http://www.rfc-editor.org/info/rfc2827>. + + [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, + "Bidirectional Forwarding Detection (BFD) for MPLS Label + Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, + June 2010, <http://www.rfc-editor.org/info/rfc5884>. + + + + + + + + + +Pignataro, et al. Standards Track [Page 7] + +RFC 7881 Seamless BFD for IPv4, IPv6, and MPLS July 2016 + + +Acknowledgements + + The authors would like to thank the BFD WG members for helping to + shape the contents of this document. In particular, significant + contributions were made by the following people: Marc Binderberger, + Jeffrey Haas, Santosh Pallagatti, Greg Mirsky, Sam Aldrin, Vengada + Prasad Govindan, Mallik Mudigonda, and Srihari Raghavan. + +Contributors + + The following are key contributors to this document: + + Tarek Saad, Cisco Systems, Inc. + Siva Sivabalan, Cisco Systems, Inc. + Nagendra Kumar, Cisco Systems, Inc. + +Authors' Addresses + + Carlos Pignataro + Cisco Systems, Inc. + + Email: cpignata@cisco.com + + + Dave Ward + Cisco Systems, Inc. + + Email: wardd@cisco.com + + + Nobo Akiya + Big Switch Networks + + Email: nobo.akiya.dev@gmail.com + + + + + + + + + + + + + + + + + +Pignataro, et al. Standards Track [Page 8] + |