A Border Gateway Protocol 4 (BGP-4)
RFC 4271
Document | Type |
RFC - Draft Standard
(January 2006; Errata)
Obsoletes RFC 1771
Was draft-ietf-idr-bgp4 (idr WG)
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Authors | Yakov Rekhter , Susan Hares , Tony Li | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4271 (Draft Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Alex Zinin | ||
Send notices to | shares@nexthop.com |
Network Working Group Y. Rekhter, Ed. Request for Comments: 4271 T. Li, Ed. Obsoletes: 1771 S. Hares, Ed. Category: Standards Track January 2006 A Border Gateway Protocol 4 (BGP-4) 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. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document discusses the Border Gateway Protocol (BGP), which is an inter-Autonomous System routing protocol. The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems (ASes) that reachability information traverses. This information is sufficient for constructing a graph of AS connectivity for this reachability from which routing loops may be pruned, and, at the AS level, some policy decisions may be enforced. BGP-4 provides a set of mechanisms for supporting Classless Inter- Domain Routing (CIDR). These mechanisms include support for advertising a set of destinations as an IP prefix, and eliminating the concept of network "class" within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including aggregation of AS paths. This document obsoletes RFC 1771. Rekhter, et al. Standards Track [Page 1] RFC 4271 BGP-4 January 2006 Table of Contents 1. Introduction ....................................................4 1.1. Definition of Commonly Used Terms ..........................4 1.2. Specification of Requirements ..............................6 2. Acknowledgements ................................................6 3. Summary of Operation ............................................7 3.1. Routes: Advertisement and Storage ..........................9 3.2. Routing Information Base ..................................10 4. Message Formats ................................................11 4.1. Message Header Format .....................................12 4.2. OPEN Message Format .......................................13 4.3. UPDATE Message Format .....................................14 4.4. KEEPALIVE Message Format ..................................21 4.5. NOTIFICATION Message Format ...............................21 5. Path Attributes ................................................23 5.1. Path Attribute Usage ......................................25 5.1.1. ORIGIN .............................................25 5.1.2. AS_PATH ............................................25 5.1.3. NEXT_HOP ...........................................26 5.1.4. MULTI_EXIT_DISC ....................................28 5.1.5. LOCAL_PREF .........................................29 5.1.6. ATOMIC_AGGREGATE ...................................29 5.1.7. AGGREGATOR .........................................30 6. BGP Error Handling. ............................................30 6.1. Message Header Error Handling .............................31 6.2. OPEN Message Error Handling ...............................31 6.3. UPDATE Message Error Handling .............................32 6.4. NOTIFICATION Message Error Handling .......................34 6.5. Hold Timer Expired Error Handling .........................34 6.6. Finite State Machine Error Handling .......................35 6.7. Cease .....................................................35 6.8. BGP Connection Collision Detection ........................35 7. BGP Version Negotiation ........................................36 8. BGP Finite State Machine (FSM) .................................37 8.1. Events for the BGP FSM ....................................38 8.1.1. Optional Events Linked to Optional Session Attributes .........................................38 8.1.2. Administrative Events ..............................42 8.1.3. Timer Events .......................................46 8.1.4. TCP Connection-Based Events ........................47 8.1.5. BGP Message-Based Events ...........................49 8.2. Description of FSM ........................................51 8.2.1. FSM Definition .....................................51Show full document text