wdiff rfc4863.original rfc4863.txt

Network Working Group Luca L. Martini
Internet Draft Cisco Systems, Inc.
Request for Comments: 4863 G. Swallow
Category: Standards Track
Expiration Date: April 2007
George Swallow Cisco Systems, Inc.

October 2006
May 2007

Wildcard Pseudowire Type

draft-ietf-pwe3-wildcard-pw-type-02.txt

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Abstract

Pseudowire signaling requires that the Pseudowire Type (PW Type) be
identical in both directions. For certain applications the
configuration of the PW Type is most easily accomplished by
configuring this information at just one PW endpoint. In any form of
LDP-based signaling, each PW endpoint must initiate the creation of a
unidirectional LSP. In order to allow the initiation of these two
LSPs to remain independent, a means of is needed for allowing the PW
endpoint
lacking (lacking a priori knowledge of the PW Type Type) to initiate the
creation of an LSP is needed. LSP. This document defines a Wildcard PW Type to
satisfy this need.

Table of Contents

1. Introduction .............................................. 3
1.1 ....................................................2
1.1. Conventions and Terminology ............................... 3
2 ................................2
2. Wildcard PW Type .......................................... 4
3 ................................................3
3. Procedures ................................................ 4
3.1 ......................................................3
3.1. Procedures when sending When Sending the wildcard Wildcard FEC .................. 4
3.2 ...................3
3.2. Procedures when receiving When Receiving the wildcard Wildcard FEC ................ 4
4 .................3
4. Security Considerations ................................... 5
5 .........................................4
5. IANA Considerations ....................................... 5
6 .............................................4
6. References ......................................................4
6.1. Normative References .......................................4
6.2. Informative References ................................................ 5 .....................................4

1. Introduction

Pseudowire signaling requires that the Pseudowire Type (PW Type) be
identical in both directions. For certain applications the configu-
ration
configuration of the PW Type is most easily accomplished by
configuring this information at just one PW endpoint. In any form of
LDP-based sig-
naling, signaling, each PW endpoint must initiate the creation of a unidirec-
tional
unidirectional LSP.

By the procedures of [CONTROL] [CONTROL], both label mapping Label Mapping messages must
carry the PW type type, and the two unidirectional mapping messages must
be in agreement. Thus within the current procedures procedures, the PW endpoint which
that lacks configuration must wait to receive a Label Mapping message
in order to learn the PW Type, prior to signaling the its unidirectional
LSP.

For certain applications this can become particularly onerous. For
example, suppose that an ingress PE Provider Edge (PE) is serving as
part of a gateway function between a layer two 2 network and layer two 2
attachment cir-
cuits circuits on remote PEs. Suppose further that the initial
setup needs to be initiated from the layer 2 network, but the layer 2
signaling does not contain sufficient information to determine the PW
Type. This
information, however However, this information is known at the PE supporting the
targeted attachment circuit.

In this situation situation, it is often desirable to allow the initiation of
the initiation of the two LSPs which that compose a pseudowire to remain independent. A
means of is needed for allowing a PW endpoint lacking (lacking a piori priori
knowledge of the PW Type Type) to initiate the creation of an LSP is
needed. LSP. This
document defines a wildcard PW Type to satisfy this need.

1.1. Conventions and Terminology

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 [KEYWORDS].

This document introduces no new terminology. However However, it assumes
that the reader is familiar with the terminology contained in
[CONTROL] and RFC 3985, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architec-
ture"
Architecture" [ARCH].

2. Wildcard PW Type

In order to allow a PE to initiate the signaling exchange for a pseu-
dowire
pseudowire without knowing the pseudowire type, a new PW Type is
defined. The proposed codepoint is 0x7fff [to be assigned by IANA]. 0x7FFF. The semantics are the following:

1. To the targeted PE, this value indicates that it is to determine
the PW Type (for both directions) and signal that in a label
mapping Label
Mapping message back to the initiating PE.

2. For the procedures of [CONTROL] [CONTROL], this PW Type is interpreted to
match any PW Type other than itself. That is is, the targeted PE
may respond with any valid PW Type other than the wildcard PW
Type.

3. Procedures

3.1. Procedures when sending When Sending the wildcard Wildcard FEC

When a PE which that is not configured to use a specific PW Type for a
particular pseudowire, pseudowire wishes to signaling signal an LSP for that pseu-
dowire, pseudowire, it
sets the PW Type to "wildcard". This indicates that the target PE
should determine the PW Type for this pseudowire.

When a Label Mapping message is received for the pseudowire, the PE
checks the PW Type.

If the PW Type can be supported, the PE uses this as the PW Type for
both directions.

If the PW Type cannot be supported or is "wildcard" "wildcard", it MUST respond
to this message with a Label Release message with an LDP Status Code
of "Generic Misconfiguration Error". Further actions are beyond the
scope of this document document, but could include notifying the associated
application (if any) or notifying network management.

3.2. Procedures when receiving When Receiving the wildcard Wildcard FEC

When a targeted PE receives a Label Mapping message indicating the
wildcard PW Type, it follows the normal procedures for checking the
AGI and TAII
Attachment Group Identifier (AGI) and Target Attachment Individual
Identifier (TAII) values. If the targeted PE is not configured to
use a specific, non-wildcard PW Type Type, it MUST respond to this message
with a Label Release message with an LDP Status Code of "Generic Misconfigu-
ration
Misconfiguration Error".

Otherwise

Otherwise, it treats the Label Mapping message as if it had indicated
the PW Type it is configured to use.

4. Security Considerations

This draft document has little impact on the security aspects of [CONTROL].
The message exchanges remain the same. However However, a malicious agent
attempting to connect to an access circuit would require one less
piece of information. To mitigate against this, a pseudowire control
entity receiving a request containing the wildcard FEC type SHOULD
only proceed with setup if explicitly configured to do so for the
particular AI in the TAI. Further, the reader should note the secu-
rity
security considerations of [CONTROL] [CONTROL], in general general, and those
pertaining to the Generalized ID PWid FEC Element Element, in particular.

5. IANA Considerations

This document requests

IANA has made the following allocation be made from the IETF consensus range
of the "Pseudowire Type" registry as defined in [IANA].

PW Type Description

0x7FFF (TBA) Wildcard

6. References

6.1. Normative References

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

[ARCH] Bryant, S. and P. Pate, "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
March 2005.

[CONTROL] Martini, L., et al., Ed., Rosen, E., El-Aawar, N., Smith, T.,
and G. Heron, "Pseudowire Setup and Maintenance using Using
the Label Distribution Protocol", Protocol (LDP)", RFC 4447, April
2006.

[IANA] Martini, L., and Townsley, M., "IANA Allocations for
pseudo Wire Pseudowire Edge to
Edge Emulation (PWE3)", BCP 116, RFC 4447, 4446, April 2006.

6.2. Informative References

[ARCH] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire
Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985,
March 2005.

Authors' Addresses

Luca Martini
Cisco Systems
9155 East Nichols Avenue, Suite 400
Englewood, CO, 80112
Email:

EMail: lmartini@cisco.com

George Swallow
Cisco Systems
1414 Massachusetts Ave,
Boxborough, MA 01719
Email:

EMail: swallow@cisco.com

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