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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