Node behavior upon originating and receiving Resource ReserVation Protocol (RSVP) Path Error message
draft-vasseur-mpls-3209-patherr-01

Networking Working Group                                     JP. Vasseur
Internet-Draft                                           George. Swallow
Intended status: Best Current                         Cisco Systems, Inc
Practice                                                  Adrian. Farrel
Expires: April 21, 2007                               Old Dog Consulting
                                                        October 18, 2006


   Node behavior upon originating and receiving Resource ReserVation
                   Protocol (RSVP) Path Error message
                 draft-vasseur-mpls-3209-patherr-01.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

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) Path Error message and to the behavior of a node receiving an
   RSVP Path Error message for a particular Multi-Protocol Label
   Switching - Traffic Engineering (MPLS-TE) Label Switched Path (LSP).



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   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.  Protocol behavior . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Behavior at Detecting Nodes . . . . . . . . . . . . . . . . 4
     1.2.  Behavior at Receiving Nodes . . . . . . . . . . . . . . . . 4
     1.3.  Data Plane Behavior . . . . . . . . . . . . . . . . . . . . 5
   2.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   5.  URLs  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9





























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1.  Protocol behavior

   [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.  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 as defined in [RFC2205] is as
   follows:

   <PathErr message> ::= <Common Header> [ <INTEGRITY> ]
                         <SESSION> <ERROR_SPEC>
                         [ <POLICY_DATA> ...]
                         [ <sender descriptor> ]

   <sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
                              [ <ADSPEC> ]


   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 an 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 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.  A full list can be seen at Section 5.  The
   error conditions fall into two categories: - fatal errors represent
   disruptive conditions for a TE LSP, - non-fatal errors are non-



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   disruptive conditions which have occurred for this TE LSP.
   Additionally, PathErr messages may be used in two circumstances: -
   during TE LSP establishment, - 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 detect (and therefore report using
   PathErr messages) errors, 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.  Section 2
   provides a list of the currently defined PathErr Error Codes and
   Error Values and indicates for each whether it is fatal or non-fatal.

1.1.  Behavior at Detecting Nodes

   In the case of fatal errors, 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.

1.2.  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] a node
   receiving a PathErr message takes no action upon it and consequently
   it 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.




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1.3.  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.


2.  IANA Considerations

   IANA maintains a registry of RSVP Error Codes and Error Values at
   Section 5.  The registry is labeled "Resource ReSerVation Protocol
   (RSVP) Parameters" / "Error Codes and Values" IANA is requested to
   add a column to this registry to indicate for each Error Code / Error
   Value combination whether the error reported constitutes a fatal or
   non-fatal error condition if the error is seen in an MPLS-TE system.
   It is suggested that the column in headed "MPLS-TE Fatal" and contain
   one of three values: Yes - The error condition represents a fatal
   condition as described in this document when applied to an MPLS TE
   LSP.  No - The error condition represents a non-fatal condition as
   described in this document when applied to an MPLS TE LSP.  N/A - The
   error condition cannot be applied to an MPLS TE LSP.  IANA should
   require that all new assignments from this registry provide
   information in this column.  In order to update this registry for the
   creation of this column, the table below supplies the setting of the
   column for each existing entry in the registry.  IANA is requested to
   transfer this information into the registry.  Note that only the
   Error Code and Error Value numbers are supplied here.  No change to
   any of the other registry fields is implied.

  Error code    Error Value    Reference      MPLS-TE Fatal
     ------------+--------------+--------------+--------------
     0             Any            [RFC2205]      N/A
     1             Any            [RFC2205]      N/A
     2             5              [RFC2750]      Yes
                   100            [RFC3476]      N/A
                   101            [RFC3476]      N/A
                   102            [RFC4495]      N/A
                   Any other      [RFC2205]      N/A
     3             Any            [RFC2205]      N/A
     4             Any            [RFC2205]      N/A
     5             Any            [RFC2205]      Yes
     6             Any            [RFC2205]      N/A
     7             Any            [RFC2205]      N/A
     8             Any            [RFC2205]      N/A
     9             Any            [RFC2205]      N/A
     10            Any            [RFC2205]      N/A
     11            Any            [RFC2205]      N/A
     12            Any            [RFC2205]      N/A



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     13            Any            [RFC2205]
     14            Any            [RFC2205]
     15            Any            [RFC2205]      N/A
     16            Any            [RFC2205]      N/A
     17            Any            [RFC2205]      N/A
     18            Any            [RFC2205]      N/A
     19            Any            [RFC2205]      N/A
     20            Any            [RFC2205]      N/A
     21            Any            [RFC2205]
     22            Any            [RFC2205]
     23            Any            [RFC2205]
     24            1              [RFC3209]      Yes
                   2              [RFC3209]      Yes
                   3              [RFC3209]      Yes
                   4              [RFC3209]      Yes
                   5              [RFC3209]      Yes
                   6              [RFC3209]      Yes
                   7              [RFC3209]      Yes
                   8              [RFC3209]      Yes
                   9              [RFC3209]      Yes
                   10             [RFC3209]      Yes
                   11             [RFC3473]      Yes
                   12             [RFC3473]      Yes
                   13             [RFC3473]      Yes
                   14             [RFC3473]      Yes
                   15             [RFC3473]      Yes
                   16             [RFC3473]      Yes
                   100            [RFC3476]      N/A
                   101            [RFC3476]      N/A
                   102            [RFC3476]      N/A
                   103            [RFC3474]      N/A
                   104            [RFC3474]      N/A
                   105            [RFC3474]      N/A
                   106            [RFC3474]      N/A
     25            1              [RFC3209]      No
                   2              [RFC3209]      No
                   3              [RFC3209]      No
                   4              [RFC3473]      No
                   5              [RFC3473]      No
                   6              [draft-ietf-ccamp-loose-path-reopt] No
                   7              [draft-ietf-ccamp-loose-path-reopt] No
                   8              [draft-ietf-ccamp-loose-path-reopt] No
     26            Any            [RFC3175]      N/A
     27            Any            [RFC3270]      N/A
     28            Any            [RFC4124]      Yes
     29            Any            [RFC4420]
     30            Any            [RFC4420]




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3.  Security Considerations

   This document does not define any new procedures, but clarifies those
   defined in other documents where security considerations are already
   specified.  This document does not raise specific security issues
   beyond those of existing MPLS-TE.  By clarifying the procedures, this
   document reduces the security risk introduced by non-conformant
   implementations.


4.  Acknowledgements

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


5.  URLs

   [IANA-URL] http://www.iana.org/numbers.html


6.  Normative References

   [I-D.ietf-ccamp-loose-path-reopt]
              Vasseur, J., "Reoptimization of Multiprotocol Label
              Switching (MPLS) Traffic Engineering  (TE) loosely routed
              Label Switch Path (LSP)",
              draft-ietf-ccamp-loose-path-reopt-02 (work in progress),
              February 2006.

   [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.




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   [RFC4495]  Polk, J. and S. Dhesikan, "A Resource Reservation Protocol
              (RSVP) Extension for the Reduction of Bandwidth of a
              Reservation Flow", RFC 4495, May 2006.


Authors' Addresses

   JP Vasseur
   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


   Adrian Farrel
   Old Dog Consulting


   Email: adrian@olddog.co.uk





















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