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Versions: (draft-vasseur-mpls-3209-patherr) 00 01 02 03 04 05 06 RFC 5711

Networking Working Group                                JP. Vasseur, Ed.
Internet-Draft                                           George. Swallow
Intended status: Standards Track                      Cisco Systems, Inc
Expires: April 1, 2010                                        Ina. Minei
                                                        Juniper Networks
                                                      September 28, 2009


   Node behavior upon originating and receiving Resource ReserVation
                   Protocol (RSVP) Path Error message
                  draft-ietf-mpls-3209-patherr-06.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Abstract

   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 Multi-Protocol Label Switching (MPLS) and Generalized MPLS
   (GMPLS) Traffic Engineering Label Switched Path (TE LSP).  This
   document does not define any new protocol extensions.

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].


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Protocol behavior . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  Behavior at Detecting Nodes . . . . . . . . . . . . . . . . 4
     2.2.  Behavior at Receiving Nodes . . . . . . . . . . . . . . . . 4
     2.3.  Data Plane Behavior . . . . . . . . . . . . . . . . . . . . 5
   3.  RSVP PathErr Messages For a Preempted TE LSP  . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6



















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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 Multi-Protocol 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 Traffic Engineering Label Switched Path
   (TE LSP) where the term preemption is defined in [RFC3209].


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 Multi-Protocol Label Switching (MPLS) Traffic
   Engineered Label Switched Paths (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 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 Section 2.2 of [RFC3209] and will
   not be repeated here.



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   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 which have occurred
      for this TE LSP

   PathErr messages may be used in two circumstances:

   o  During TE LSP establishment,

   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 re-
   statement 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 SHOULD send a PathErr message
   reporting the error condition, and clears 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.

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 [RFC2205]
   Section 3.7.1, a node receiving a PathErr message takes no action
   upon it and consequently it must not clear Path or Resv control plane



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   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-code 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"

   In both cases, these are fatal errors.


4.  IANA Considerations

   This document does not define any new protocol extensions and thus no
   action is requested to IANA.


5.  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
   clarifying the procedures, this document reduces the security risk



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   introduced by non-conformant implementations.  See
   [I-D.ietf-mpls-mpls-and-gmpls-security-framework] for further
   discussion of MPLS security issues.


6.  Acknowledgements

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


7.  References

7.1.  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.

7.2.  Informative References

   [I-D.ietf-mpls-mpls-and-gmpls-security-framework]
              Fang, L. and M. Behringer, "Security Framework for MPLS
              and GMPLS Networks",
              draft-ietf-mpls-mpls-and-gmpls-security-framework-06 (work
              in progress), July 2009.











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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,   94089


   Email: ina@juniper.net
























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