RFC 5711

Node Behavior upon Originating and Receiving Resource Reservation Protocol (RSVP) Path Error Messages

📅 published January 2010, from ietf

RFC 5711 🎀 Node Behavior upon Originating and Receiving Resource Reservation Protocol (RSVP) Path Error Messages

Okay bestie, this one is a Standards Track doc from January 2010 🌸 It was written by JP Vasseur (editor), G. Swallow, and I. Minei, with JP and George at Cisco Systems, Inc. and Ina at Juniper Networks. The ISSN is 2070-1721. It updates RFC 3209, which is the big RSVP-TE extensions doc, and the title block doesn't list anything it obsoletes. The whole point is to write down how nodes should act when they send and receive RSVP Path Error messages for a preempted TE LSP. 💅

Abstract ✨

Okay so this doc is basically "here's the common practice" 🍓 It's about nodes that send and receive RSVP Traffic Engineering Path Error messages when a TE LSP in MPLS or GMPLS gets preempted, which just means it gets kicked off its spot because something more important needs it. For the details on preemption, go check RFC 3209. And honestly the best part is that this doc doesn't invent any new protocol extensions 🧚

Status of This Memo 🦋

This is an Internet Standards Track document, meaning it's an official IETF product that has the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). If you want more on how Internet Standards work, check Section 2 of RFC 5741.

If you want the current status, any errata, or a place to leave feedback, the page lives at http://www.rfc-editor.org/info/rfc5711 💜

Copyright Notice 🌈

This doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents, which you can find at http://trustee.ietf.org/license-info as they were in effect when it was published. Read those carefully because they spell out your rights and restrictions. Any Code Components pulled out of this document must include the Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as the Simplified BSD License says 🫶

Table of Contents 📚

1. Introduction ....................................................3
   1.1. Requirements Language ......................................3
2. Protocol Behavior ...............................................3
   2.1. Behavior at Detecting Nodes ................................4
   2.2. Behavior at Receiving Nodes ................................5
   2.3. Data-Plane Behavior ........................................5
3. RSVP PathErr Messages for a Preempted TE LSP ....................5
4. Security Considerations .........................................5
5. Acknowledgements ................................................6
6. References ......................................................6
   6.1. Normative References .......................................6
   6.2. Informative References .....................................6

1. Introduction 🌸

Okay so the aim here is to describe what a node does when it's sending an RSVP-TE Path Error message, and what a node does when it's receiving one, specifically for a preempted MPLS or GMPLS TE LSP. For preemption details, see [RFC3209] 🎀

RFC 2205 defines two RSVP error message types, PathErr and ResvErr, which get generated when something goes wrong. PathErr messages report errors and travel upstream toward the head-end of the flow. ResvErr messages travel downstream toward the tail-end. It's giving two-way street vibes 🚦

This doc only covers PathErr message processing for the specific case of a preempted TE LSP, where preemption is defined in [RFC3209] 💖

1.1. Requirements Language 💅

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]. Those are the official BCP 14 power words, so they keep their exact force 🔥

2. Protocol Behavior 🦋

PathErr messages get routed hop-by-hop, using the path state that was set up when a Path message traveled through the network from the head-end to the tail-end. It's basically following the breadcrumbs 🍞

As RFC 2205 says, PathErr messages don't change the state of any node they pass through. They just get reported back to the head-end of the TE LSP ✨

The format of the PathErr message is defined in Section 3. of [RFC2205] 📝

The ERROR_SPEC object includes the IP address of the node that detected the error, called the Error Node Address. It also says what went wrong through two fields. The Error Code field tells you the category of the error, like Policy Control Failure or Unknown object class. The Error Value field narrows it down to a more precise error. RFC 3209 extends RSVP from RFC 2205 for managing MPLS-TE LSPs, and it adds several more conditions that can trigger a PathErr message, with new error codes and error values that stretch the list from RFC 2205. The exact circumstances for when a TE LSP gets preempted and when these PathErr messages go out are defined in [RFC3209], and this doc isn't going to repeat them 🙈

Values for the Error Code and Error Value fields, from [RFC2205], [RFC3209], and other docs, are kept in a registry maintained by the IANA 📋

The error conditions fall into two categories:

Fatal errors represent disruptive conditions for a TE LSP.
Non-fatal errors are non-disruptive conditions that have occurred for this TE LSP.

PathErr messages may be used in two circumstances:

during TE LSP establishment, and
after a TE LSP has been successfully established.

Nodal behavior depends on which combination of the four cases listed above applies. The next sections describe the expected behavior at nodes that do a preemption action for a TE LSP (and therefore report using PathErr messages), and at nodes that receive PathErr messages. This text clarifies and restates the procedures in [RFC3209], and it doesn't define any new behavior 🌈

2.1. Behavior at Detecting Nodes 💥

For fatal errors ("Hard Preemption"; see Section 4.7.3 of [RFC3209] ), the detecting node MUST send a PathErr message reporting the error condition, and MUST clear the corresponding Path and Resv (control plane) states. So the data-plane resources for that TE LSP also get released, which means traffic gets disrupted. It's worth noting, though, that with fatal errors the LSP has usually already failed in the data plane, so traffic was already disrupted anyway 😭 When the error happens during LSP establishment, things are different from when it happens on an active LSP, because no traffic flows until the LSP is fully established.

For non-fatal errors, the detecting node should send a PathErr message, and must not clear control plane or data plane state 🫶

2.2. Behavior at Receiving Nodes 🧚

The nodes that receive PathErr messages are all the nodes along the TE LSP's path upstream of the node that detected the error, including the head-end node. Per Section 3.7.1 of [RFC2205], a node receiving a PathErr message takes no action on it, so the node must not clear Path or Resv control-plane or data-plane state. This is true whether the error is fatal or non-fatal 💅 RSVP states should only be affected when a PathTear or ResvTear message comes in, or when a Path or Resv state times out. How those events get processed is outside the scope of this document.

Note that [RFC3473] defines a Path_State_Removed flag in the ERROR_SPEC object carried on a PathErr message. This field may be set to change how upstream nodes that receive the PathErr message behave. When it's set, the flag means the message sender has removed Path state (and any associated Resv and data-plane state) for the TE LSP. The message receiver should do the same before forwarding the message, but it may keep state and clear the flag before forwarding 🦋

2.3. Data-Plane Behavior ⭐

If a node clears either or both the Path or the Resv state of a TE LSP, it MUST also free up the data-plane resources that were allocated to that TE LSP. Don't leave orphaned resources hanging around, bestie 👑

3. RSVP PathErr Messages for a Preempted TE LSP 🌸

Two Error Codes have been defined to report a preempted TE LSP:

As defined in [RFC2750]: Error Code=2: "Policy Control Failure", Error Value=5: "Flow was preempted"
As defined in [RFC2205], Error Code=12: "Service preempted"

Both of these are fatal errors 💀

4. Security Considerations 🔥

Okay this part is serious, so listen up 🙈 This document doesn't define any new procedures. It just clarifies the ones already defined in other docs, where the security considerations are already specified in [RFC3209] and [RFC3473]. It doesn't raise any specific security issues beyond the ones that already exist for MPLS-TE. By clarifying the procedures, this doc lowers the security risk that comes from non-conformant implementations. For more on MPLS security issues, see [SEC_FMWK] 🛡️✨

5. Acknowledgements 💜

The authors would like to thank Carol Iturralde, Ashok Narayanan, Rom Reuther, and Reshad Rahman, who are absolutely iconic 👑

6. References 🧚

6.1. Normative References 💖

[RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2205]   Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
            Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
            Functional Specification", RFC 2205, September 1997.

[RFC2750]   Herzog, S., "RSVP Extensions for Policy Control",
            RFC 2750, January 2000.

[RFC3209]   Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
            and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
            Tunnels", RFC 3209, December 2001.

[RFC3473]   Berger, L., "Generalized Multi-Protocol Label Switching
            (GMPLS) Signaling Resource ReserVation Protocol-Traffic
            Engineering (RSVP-TE) Extensions", RFC 3473,
            January 2003.

6.2. Informative References 🌈

[SEC_FMWK]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
            Networks", Work in Progress, October 2009.

Authors' Addresses 🎀

JP Vasseur (editor)
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA  01719
USA

EMail: jpv@cisco.com


George Swallow
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA  01719
USA

EMail: swallow@cisco.com


Ina Minei
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA  94089
USA

EMail: ina@juniper.net

📦 where this page comes from

ietf: rfc5711 2010-01
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms