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rfc:rfc5711

Internet Engineering Task Force (IETF) JP. Vasseur, Ed. Request for Comments: 5711 G. Swallow Updates: 3209 Cisco Systems, Inc. Category: Standards Track I. Minei ISSN: 2070-1721 Juniper Networks

                                                          January 2010
 Node Behavior upon Originating and Receiving Resource Reservation
                Protocol (RSVP) Path Error Messages

Abstract

 The aim of this document is to describe a common practice with regard
 to the behavior of nodes that send and receive a Resource Reservation
 Protocol (RSVP) Traffic Engineering (TE) Path Error messages for a
 preempted Multiprotocol Label Switching (MPLS) or Generalized MPLS
 (GMPLS) Traffic Engineering Label Switched Path (TE LSP).  (For
 reference to the notion of TE LSP preemption, see RFC 3209.)  This
 document does not define any new protocol extensions.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc5711.

Vasseur, et al. Standards Track [Page 1] RFC 5711 Node Behavior with RSVP PathErr January 2010

Copyright Notice

 Copyright (c) 2010 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

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

Vasseur, et al. Standards Track [Page 2] RFC 5711 Node Behavior with RSVP PathErr January 2010

1. Introduction

 The aim of this document is to describe a common practice with regard
 to the behavior of a node sending a Resource Reservation Protocol
 (RSVP) Traffic Engineering (TE) Path Error message and to the
 behavior of a node receiving an RSVP Path Error message for a
 preempted Multiprotocol Label Switching (MPLS) and Generalized MPLS
 (GMPLS) Traffic Engineering Label Switched Path (TE LSP).  (For
 reference to the notion of TE LSP preemption, see [RFC3209]).
 [RFC2205] defines two RSVP error message types: PathErr and ResvErr
 that are generated when an error occurs.  Path Error messages
 (PathErr) are used to report errors and travel upstream toward the
 head-end of the flow.  Resv Error messages (ResvErr) travel
 downstream toward the tail-end of the flow.
 This document describes only PathErr message processing for the
 specific case of a preempted TE LSP, where the term 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].

2. Protocol Behavior

 PathErr messages are routed hop-by-hop using the path state
 established when a Path message is routed through the network from
 the head-end to its tail-end.
 As stated in [RFC2205], PathErr messages do not modify the state of
 any node through which they pass; they are only reported to the head-
 end of the TE LSP (Traffic Engineering Label Switched Path).
 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 (Error Node Address), and specifies the error
 through two fields.  The Error Code field encodes the category of the
 error, for example, Policy Control Failure or Unknown object class.
 The Error Value field qualifies the error code to indicate the error
 with more precision.  [RFC3209] extends RSVP as defined in [RFC2205]
 for the management of MPLS-TE LSPs.  [RFC3209] specifies several
 additional conditions that trigger the sending of a RSVP PathErr
 message for which new error codes and error values have been defined

Vasseur, et al. Standards Track [Page 3] RFC 5711 Node Behavior with RSVP PathErr January 2010

 that extend the list defined in [RFC2205].  The exact circumstances
 under which a TE LSP is preempted and such PathErr messages are sent
 are defined in [RFC3209] and will not be repeated here.
 Values for the Error Code and Error Value fields defined in
 [RFC2205], [RFC3209], and other documents are maintained in a
 registry by the IANA.
 The error conditions fall into two categories:
 o  Fatal errors represent disruptive conditions for a TE LSP.
 o  Non-fatal errors are non-disruptive conditions that have occurred
    for this TE LSP.
 PathErr messages may be used in two circumstances:
 o  during TE LSP establishment, and
 o  after a TE LSP has been successfully established.
 Nodal behavior is dependent on which combination of the four cases
 listed above applies.  The following sections describe the expected
 behavior at nodes that perform a preemption action for a TE LSP (and
 therefore report using error PathErr messages), and at nodes that
 receive PathErr messages.  This text is a clarification and
 restatement of the procedures set out in [RFC3209] and does not
 define any new behavior.

2.1. Behavior at Detecting Nodes

 In the case of 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.  A direct implication is that the data-plane
 resources of such a TE LSP are also released, thus resulting in
 traffic disruption.  It should be noted, however, that in fatal error
 cases, the LSP has usually already failed in the data plane, and
 traffic has already been disrupted.  When the error arises during LSP
 establishment, the implications are different to when it arises on an
 active LSP since no traffic flows until the LSP has been fully
 established.  In the case of non-fatal errors, the detecting node
 should send a PathErr message, and must not clear control plane or
 data plane state.

Vasseur, et al. Standards Track [Page 4] RFC 5711 Node Behavior with RSVP PathErr January 2010

2.2. Behavior at Receiving Nodes

 Nodes that receive PathErr messages are all of the nodes along the
 path of the TE LSP upstream of the node that detected the error.
 This includes the head-end node.  In accordance with Section 3.7.1 of
 [RFC2205], a node receiving a PathErr message takes no action upon
 it, and consequently the node must not clear Path or Resv control-
 plane or data-plane state.  This is true regardless of whether the
 error condition reported by the PathErr is fatal or non-fatal.  RSVP
 states should only be affected upon receiving a PathTear or ResvTear
 message, or in the event of a Path or Resv state timeout.  Further
 discussion of the processing of these events 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 the behavior of upstream nodes that receive the PathErr
 message.  When set, the flag indicates that the message sender has
 removed Path state (and any associated Resv and data-plane state) for
 the TE LSP.  The message receiver should do likewise before
 forwarding the message, but may retain state and clear the flag
 before forwarding the message.

2.3. Data-Plane Behavior

 Any node clearing either or both the Path or the Resv state of a TE
 LSP MUST also free up the data-plane resources allocated to the
 corresponding TE LSP.

3. RSVP PathErr Messages for a Preempted TE LSP

 Two Error Codes have been defined to report a preempted TE LSP:
 o  As defined in [RFC2750]: Error Code=2: "Policy Control Failure",
    Error Value=5: "Flow was preempted"
 o  As defined in [RFC2205], Error Code=12: "Service preempted"
 They are both fatal errors.

4. Security Considerations

 This document does not define any new procedures, but clarifies those
 defined in other documents where security considerations are already
 specified in [RFC3209] and [RFC3473].  This document does not raise
 specific security issues beyond those of existing MPLS-TE.  By

Vasseur, et al. Standards Track [Page 5] RFC 5711 Node Behavior with RSVP PathErr January 2010

 clarifying the procedures, this document reduces the security risk
 introduced by non-conformant implementations.  See [SEC_FMWK] for
 further discussion of MPLS security issues.

5. Acknowledgements

 The authors would like to thank Carol Iturralde, Ashok Narayanan, Rom
 Reuther, and Reshad Rahman.

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.

Vasseur, et al. Standards Track [Page 6] RFC 5711 Node Behavior with RSVP PathErr January 2010

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

Vasseur, et al. Standards Track [Page 7]

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