Graceful Restart Mechanism for Label Distribution Protocol
RFC 3478
Document | Type | RFC - Proposed Standard (February 2003; No errata) | |
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Authors | Manoj Leelanivas , Yakov Rekhter , Rahul Aggarwal | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3478 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Scott Bradner | ||
Send notices to | (None) |
Network Working Group M. Leelanivas Request for Comments: 3478 Y. Rekhter Category: Standards Track Juniper Networks R. Aggarwal Redback Networks February 2003 Graceful Restart Mechanism for Label Distribution Protocol 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 (2003). All Rights Reserved. Abstract This document describes a mechanism that helps to minimize the negative effects on MPLS traffic caused by Label Switching Router's (LSR's) control plane restart, specifically by the restart of its Label Distribution Protocol (LDP) component, on LSRs that are capable of preserving the MPLS forwarding component across the restart. The mechanism described in this document is applicable to all LSRs, both those with the ability to preserve forwarding state during LDP restart and those without (although the latter needs to implement only a subset of the mechanism described in this document). Supporting (a subset of) the mechanism described here by the LSRs that can not preserve their MPLS forwarding state across the restart would not reduce the negative impact on MPLS traffic caused by their control plane restart, but it would minimize the impact if their neighbor(s) are capable of preserving the forwarding state across the restart of their control plane and implement the mechanism described here. The mechanism makes minimalistic assumptions on what has to be preserved across restart - the mechanism assumes that only the actual MPLS forwarding state has to be preserved; the mechanism does not require any of the LDP-related states to be preserved across the restart. Leelanivas, et al. Standards Track [Page 1] RFC 3478 Graceful Restart Mechanism for LDP February 2003 The procedures described in this document apply to downstream unsolicited label distribution. Extending these procedures to downstream on demand label distribution is for further study. 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 BCP 14, RFC 2119 [RFC2119]. 1. Motivation For the sake of brevity in the context of this document, by "the control plane" we mean "the LDP component of the control plane". For the sake of brevity in the context of this document, by "MPLS forwarding state" we mean either <incoming label -> (outgoing label, next hop)> (non-ingress case), or <FEC->(outgoing label, next hop)> (ingress case) mapping. In the case where a Label Switching Router (LSR) could preserve its MPLS forwarding state across restart of its control plane, specifically its LDP component [LDP], it is desirable not to perturb the LSPs going through that LSR (specifically, the LSPs established by LDP). In this document, we describe a mechanism, termed "LDP Graceful Restart", that allows the accomplishment of this goal. The mechanism described in this document is applicable to all LSRs, both those with the ability to preserve forwarding state during LDP restart and those without (although the latter need to implement only a subset of the mechanism described in this document). Supporting (a subset of) the mechanism described here by the LSRs that can not preserve their MPLS forwarding state across the restart would not reduce the negative impact on MPLS traffic caused by their control plane restart, but it would minimize the impact if their neighbor(s) are capable of preserving the forwarding state across the restart of their control plane and implement the mechanism described here. The mechanism makes minimalistic assumptions on what has to be preserved across restart - the mechanism assumes that only the actual MPLS forwarding state has to be preserved. Clearly this is the minimum amount of state that has to be preserved across the restart in order not to perturb the LSPs traversing a restarting LSR. The mechanism does not require any of the LDP-related states to be preserved across the restart. Leelanivas, et al. Standards Track [Page 2] RFC 3478 Graceful Restart Mechanism for LDP February 2003Show full document text