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authorThomas Voss <mail@thomasvoss.com> 2024-11-27 20:54:24 +0100
committerThomas Voss <mail@thomasvoss.com> 2024-11-27 20:54:24 +0100
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+Network Working Group C. Metz
+Request for Comments: 5003 L. Martini
+Category: Standards Track Cisco Systems Inc.
+ F. Balus
+ Alcatel-Lucent
+ J. Sugimoto
+ Nortel Networks
+ September 2007
+
+
+ Attachment Individual Identifier (AII) Types for Aggregation
+
+Status of This Memo
+
+ This document specifies an Internet standards track protocol for the
+ Internet community, and requests discussion and suggestions for
+ improvements. Please refer to the current edition of the "Internet
+ Official Protocol Standards" (STD 1) for the standardization state
+ and status of this protocol. Distribution of this memo is unlimited.
+
+Abstract
+
+ The signaling protocols used to establish point-to-point pseudowires
+ include type-length-value (TLV) fields that identify pseudowire
+ endpoints called attachment individual identifiers (AIIs). This
+ document defines AII structures in the form of new AII TLV fields
+ that support AII aggregation for improved scalability and Virtual
+ Private Network (VPN) auto-discovery. It is envisioned that this
+ would be useful in large inter-domain virtual private wire service
+ networks where pseudowires are established between selected local and
+ remote provider edge (PE) nodes based on customer need.
+
+Table of Contents
+
+ 1. Introduction ....................................................2
+ 2. Specification of Requirements ...................................3
+ 3. Structure for the New AII Type ..................................3
+ 3.1. AII Type 1 .................................................3
+ 3.2. AII Type 2 .................................................3
+ 4. IANA Considerations .............................................5
+ 5. Security Considerations .........................................5
+ 6. Acknowledgments .................................................5
+ 7. Normative References ............................................5
+ 8. Informative References ..........................................5
+
+
+
+
+
+
+
+Metz, et al. Standards Track [Page 1]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+1. Introduction
+
+ [RFC4447] defines the signaling mechanisms for establishing point-
+ to-point pseudowires (PWs) between two provider edge (PE) nodes.
+ When a PW is set up, the LDP signaling messages include a forwarding
+ equivalence class (FEC) element containing information about the PW
+ type and an endpoint identifier used in the selection of the PW
+ forwarder that binds the PW to the attachment circuit at each end.
+
+ There are two types of FEC elements defined for this purpose: PWid
+ FEC (type 128) and the Generalized ID (GID) FEC (type 129). The PWid
+ FEC element includes a fixed-length 32-bit value called the PWid that
+ serves as an endpoint identifier. The same PWid value must be
+ configured on the local and remote PE prior to PW setup.
+
+ The GID FEC element includes TLV fields for attachment individual
+ identifiers (AIIs) that, in conjunction with an attachment group
+ identifier (AGI), serve as PW endpoint identifiers. The endpoint
+ identifier on the local PE (denoted as <AGI, source AII, or SAII>) is
+ called the source attachment identifier (SAI) and the endpoint
+ identifier on the remote PE (denoted as <AGI, target AII, or TAII>)
+ is called the target attachment identifier (TAI). The SAI and TAI
+ can be distinct values. This is useful for applications and
+ provisioning models where the local PE (with a particular SAI) does
+ not know and must somehow learn (e.g., via Multiprotocol BGP (MP-BGP)
+ auto-discovery) of remote TAI values prior to launching PW setup
+ messages towards the remote PE.
+
+ The use of the GID FEC TLV provides the flexibility to structure
+ (source or target) AII values to best fit the needs of a particular
+ application or provisioning model [L2VPN-SIG]. For example, an AII
+ structure that enables many individual AII values to be identified as
+ a single value could significantly reduce the burden on AII
+ distribution mechanisms (e.g., MP-BGP) and on PE memory needed to
+ store this AII information. It should be noted that Pseudowire
+ Emulation Edge-to-Edge (PWE3) signaling messages will always include
+ a fully qualified AII value.
+
+ An AII that is globally unique would facilitate PW management and
+ security in large inter-AS (autonomous system) and inter-provider
+ environments. Providers would not have to worry about AII value
+ overlap during provisioning or the need for AII network address
+ translation (NAT) boxes during signaling. Globally unique AII values
+ could aid in troubleshooting and could be subjected to source-
+ validity checks during AII distribution and signaling. An AII
+ automatically derived from a provider's existing IP address space can
+ simplify the provisioning process.
+
+
+
+
+Metz, et al. Standards Track [Page 2]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+ This document defines an AII structure based on [RFC4447] that:
+
+ o Enables many discrete attachment individual identifiers to be
+ summarized into a single AII summary value. This will enhance
+ scalability by reducing the burden on AII distribution mechanisms
+ and on PE memory.
+
+ o Ensures global uniqueness if desired by the provider. This will
+ facilitate Internet-wide PW connectivity and provide a means for
+ providers to perform source validation on the AII distribution
+ (e.g., MP-BGP) and signaling (e.g., LDP) channels.
+
+ This is accomplished by defining new AII types and the associated
+ formats of the value field.
+
+2. Specification of Requirements
+
+ 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. Structure for the New AII Type
+
+ [RFC4447] defines the format of the GID FEC TLV and the use and
+ semantics of the attachment group identifier (AGI).
+
+3.1. AII Type 1
+
+ AII Type 1 has been allocated by IANA for use with provisioning
+ models requiring a fixed-length 32-bit value [L2VPN-SIG]. This value
+ is unique on the local PE.
+
+3.2. AII Type 2
+
+ The AII Type 2 structure permits varying levels of AII summarization
+ to take place, thus reducing the scaling burden on the aforementioned
+ AII distribution mechanisms and PE memory. In other words, it no
+ longer becomes necessary to distribute or configure all individual
+ AII values (which could number in the tens of thousands or more) on
+ local PEs prior to establishing PWs to remote PEs. The details of
+ how and where the aggregation of AII values is performed and then
+ distributed as AII reachability information are not discussed in this
+ document.
+
+ AII Type 2 uses a combination of a provider's globally unique
+ identifier (Global ID), a 32-bit prefix field, and a 4-octet
+ attachment circuit identifier (AC ID) field to create globally unique
+ AII values.
+
+
+
+Metz, et al. Standards Track [Page 3]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+ The encoding of AII Type 2 is shown in Figure 1.
+
+ 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | AII Type=02 | Length | Global ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Global ID (contd.) | Prefix |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | Prefix (contd.) | AC ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | AC ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ Figure 1. AII Type 2 TLV Structure
+
+ o AII Type = 0x02
+
+ o Length = length of value field in octets. The length is set to
+ 12.
+
+ o Global ID = This is a 4-octet field containing a value that is
+ unique to the provider. The global ID can contain the 2-octet or
+ 4-octet value of the provider's Autonomous System Number (ASN).
+ It is expected that the global ID will be derived from the
+ globally unique ASN of the autonomous system hosting the PEs
+ containing the actual AIIs. The presence of a global ID based on
+ the provider's ASN ensures that the AII will be globally unique.
+
+ If the global ID is derived from a 2-octet AS number, then the
+ two high-order octets of this 4-octet field MUST be set to zero.
+
+ Please note that the use of the provider's ASN as a global ID
+ DOES NOT have anything at all to do with the use of the ASN in
+ protocols such as BGP.
+
+ o Prefix = The 32-bit prefix is a value assigned by the provider or
+ it can be automatically derived from the PE's /32 IPv4 loopback
+ address. Note that, for IP reachability, it is not required that
+ the 32-bit prefix have any association with the IPv4 address
+ space used in the provider's IGP or BGP.
+
+ o Attachment Circuit (AC) ID = This is a fixed-length 4-octet field
+ used to further refine identification of an attachment circuit on
+ the PE. The inclusion of the AC ID is used to identify
+ individual attachment circuits that share a common prefix.
+
+
+
+
+
+Metz, et al. Standards Track [Page 4]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+4. IANA Considerations
+
+ IANA has allocated a value from the "Attachment Individual Identifier
+ (AII) Type" registry defined in [RFC4446].
+
+ The value for this AII type is 0x02.
+
+5. Security Considerations
+
+ AII values appear in AII distribution protocols [L2VPN-SIG] and PW
+ signaling protocols [RFC4447] and are subject to various
+ authentication schemes (i.e., MD5) if so desired.
+
+ The use of global ID values (e.g., ASN) in the inter-provider case
+ could enable a form of source-validation checking to ensure that the
+ AII value (aggregated or explicit) originated from a legitimate
+ source.
+
+6. Acknowledgments
+
+ Thanks to Carlos Pignataro, Scott Brim, Skip Booth, George Swallow,
+ and Bruce Davie for their input into this document.
+
+7. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
+ G. Heron, "Pseudowire Setup and Maintenance Using the
+ Label Distribution Protocol (LDP)", RFC 4447, April 2006.
+
+ [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to
+ Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
+
+8. Informative References
+
+ [L2VPN-SIG] Rosen, E., Luo, W., Davie, B., and V. Radoaca,
+ "Provisioning, Autodiscovery, and Signaling in L2VPNs",
+ Work in Progress, May 2006.
+
+
+
+
+
+
+
+
+
+
+
+Metz, et al. Standards Track [Page 5]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+Authors' Addresses
+
+ Luca Martini
+ Cisco Systems, Inc.
+ 9155 East Nichols Avenue, Suite 400
+ Englewood, CO, 80112
+ EMail: lmartini@cisco.com
+
+ Chris Metz
+ Cisco Systems, Inc.
+ 3700 Cisco Way
+ San Jose, Ca. 95134
+ EMail: chmetz@cisco.com
+
+ Florin Balus
+ Alcatel-Lucent
+ 701 East Middlefield Rd.
+ Mountain View, CA 94043
+ EMail: florin.balus@alcatel-lucent.com
+
+ Jeff Sugimoto
+ Nortel Networks
+ 3500 Carling Ave.
+ Ottawa, Ontario, CANADA
+ EMail: sugimoto@nortel.com
+
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+Metz, et al. Standards Track [Page 6]
+
+RFC 5003 AII Types for Aggregation September 2007
+
+
+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2007).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+ This document and the information contained herein are provided on an
+ "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+ OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
+ THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
+ OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
+ THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+ WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
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+
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+Metz, et al. Standards Track [Page 7]
+