Graceful Restart Mechanism for BGP with MPLS
RFC 4781
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RFC - Proposed Standard
(January 2007; No errata)
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2015-10-14
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IETF
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WG Document
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RFC 4781 (Proposed Standard)
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Alex Zinin
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Network Working Group Y. Rekhter
Request for Comments: 4781 R. Aggarwal
Category: Standards Track Juniper Networks
January 2007
Graceful Restart Mechanism for BGP with MPLS
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 (2007).
Abstract
A mechanism for BGP that helps minimize the negative effects on
routing caused by BGP restart has already been developed and is
described in a separate document ("Graceful Restart Mechanism for
BGP"). This document extends this mechanism to minimize the negative
effects on MPLS forwarding caused by the Label Switching Router's
(LSR's) control plane restart, and specifically by the restart of its
BGP component when BGP is used to carry MPLS labels and the LSR is
capable of preserving the MPLS forwarding state across the restart.
The mechanism described in this document is agnostic with respect to
the types of the addresses carried in the BGP Network Layer
Reachability Information (NLRI) field. As such, it works in
conjunction with any of the address families that could be carried in
BGP (e.g., IPv4, IPv6, etc.).
Rekhter & Aggarwal Standards Track [Page 1]
RFC 4781 Graceful Restart Mechanism for BGP January 2007
Table of Contents
1. Introduction ....................................................2
1.1. Specification of Requirements ..............................3
2. General Requirements ............................................3
3. Capability Advertisement ........................................4
4. Procedures for the Restarting LSR ...............................4
4.1. Case 1 .....................................................4
4.2. Case 2 .....................................................5
4.3. Case 3 .....................................................5
5. Alternative Procedures for the Restarting LSR ...................6
6. Procedures for a Neighbor of a Restarting LSR ...................6
7. Comparison between Alternative Procedures for the
Restarting LSR ..................................................7
8. Security Considerations .........................................8
9. Acknowledgments .................................................9
10. References .....................................................9
10.1. Normative References ......................................9
10.2. Informative References ....................................9
1. Introduction
In the case where a Label Switching Router (LSR) could preserve its
MPLS forwarding state across restart of its control plane, and
specifically its BGP component, and BGP is used to carry MPLS labels
(e.g., as specified in [RFC3107]), it may be desirable not to perturb
the LSPs going through that LSR (and specifically, the LSPs
established by BGP) after failure or restart of the BGP component of
the control plane. In this document, we describe a mechanism that
allows this goal to be accomplished. The mechanism described in this
document works in conjunction with the mechanism specified in
[RFC4724]. The mechanism described in this document places no
restrictions on the types of addresses (address families) that it can
support.
The mechanism described in this document is applicable to all LSRs,
both those with the ability to preserve forwarding state during BGP
restart and those without it (although the latter need to implement
only a subset of this mechanism). Supporting a subset of the
mechanism described here by the LSRs that cannot preserve their MPLS
forwarding state across the restart would not reduce the negative
impact on MPLS traffic caused by their control plane restart.
However, the impact would be minimized if their neighbor(s) are
capable of preserving the forwarding state across the restart of
their control plane, and if they implement the mechanism described
here. The subset includes all the procedures described in this
document, except the procedures in Sections 4.1, 4.2, 4.3, and 5.
Rekhter & Aggarwal Standards Track [Page 2]
RFC 4781 Graceful Restart Mechanism for BGP January 2007
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