Network Working Group Luca Martini
Internet Draft Cisco Systems, Inc.
Category: Standards Track
Expiration Date: July 2006
George Swallow
Cisco Systems, Inc.
January 2006
Target Choice of Pseudowire Type
draft-ietf-pwe3-wildcard-pw-type-00.txt
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Abstract
The Generalized PWid FEC permits a procedure know as single-sided
signaling as documented. In this procedure, one end of the
pseudowire always initiates the pseudowire setup and the target of
that label mapping message only signals in response. For certain
applications of pseudowires it is advantages to configure the
pseudowire type (PW type) at the target of the initial label mapping
message. This document specifies a means of doing this.
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Internet Draft draft-ietf-pwe3-wildcard-pw-type-00.txt January 2006
Contents
1 Introduction .............................................. 3
1.1 Conventions ............................................... 3
2 Wildcard PW Type .......................................... 3
3 Procedures ................................................ 4
4 Security Considerations ................................... 4
5 IANA Considerations ....................................... 4
6 References ................................................ 5
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1. Introduction
The Generalized PWid FEC [CONTROL] permits a procedure know as sin-
gle-sided signaling as documented in [L2VPNSIG]. In this procedure,
one end of the pseudowire always initiates the pseudowire setup. The
target router of that initial label mapping message only signals in
response. For certain applications of pseudowires it is advantages
to configure the pseudowire type (PW_Type) at the target of the ini-
tial label mapping message.
For certain applications where an igress PE is serving as part of a
gateway function between a layer two network and layer two attachment
circuits on remote PEs, the initial setup may be caused by signaling
from the layer 2 network. However, the layer 2 signaling may not
contain sufficient information to determine the PW type. This infor-
mation, however would be known at the PE supporting the targeted
attachment circuit.
By the procedures of [CONTROL] both label mapping messages must carry
the PW type and the two unidirectional mapping messages must be in
agreement. Thus within the current procedures the initiator must
specify the PW_Type.
1.1. Conventions
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].
2. Wildcard PW Type
In order to allow a PE to initiate the signaling exchange for a pseu-
dowire without knowing the pseudowire type, the following procedure
is used.
The initiating PE includes a PW type of 0x7fff [to be assigned by
IANA]. 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 message back to the initiating PE.
2. For the procedures of [CONTROL] this PW type is interpreted to
match any PW type other than itself. That is the targeted PE may
respond with any valid PW type other than the Wildcard PW type.
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Internet Draft draft-ietf-pwe3-wildcard-pw-type-00.txt January 2006
3. Procedures
A targeted PE which receives a Wildcard PW type follows the normal
procedures in checking the AGI and TAII values. If a label mapping
message has already been issued, it MUST respond to this message with
a Label_Release message.
If PE2 cannot map the TAI to one of its Forwarders, then PE2 sends a
Label Release message to PE1, with a Status Code of "Unas-
signed/Unrecognized TAI", and the processing of the Label Mapping
message is complete. Otherwise, it responds with a Label_Mapping
message with the configured PW type.
When the initiating PE receives a Label_Mapping message from the tar-
geted PE it uses this as the PW type for both directions. If it is
unable to support the PW type it MUST send a Label_Release message
for the label allocated in the Label_Mapping message which initiated
the exchange. It also SHOULD respond to the received Label_Mapping
message with a Label_Release message. Further actions are beyond the
scope of this document but could include notifying the associated
application (if any) or notifying network management.
4. Security Considerations
This draft does not impact the security aspects of [CONTROL]. The
message exchanges remain the same.
5. IANA Considerations
This document requests 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
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6. References
Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[CONTROL] Martini, L., et al., "Pseudowire Setup and
Maintenance using the Label Distribution Protocol",
draft-ietf-pwe3-control-protocol-17.txt, June 2005.
[L2VPNSIG] Rosen, E., et al., Provisioning, Autodiscovery, and
Signaling in L2VPNs", draft-ietf-l2vpn-signaling-06.txt,
September 2005.
[IANA] Martini, L., and Townsley, M., "IANA Allocations for
pseudo Wire Edge to Edge Emulation (PWE3)",
draft-ietf-pwe3-iana-allocation-17.txt, June 2005.
Authors' Addresses
Luca Martini
Cisco Systems
9155 East Nichols Avenue, Suite 400
Englewood, CO, 80112
Email: lmartini@cisco.com
George Swallow
Cisco Systems
1414 Massachusetts Ave,
Boxborough, MA 01719
Email: swallow@cisco.com
Copyright Notice
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
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Internet Draft draft-ietf-pwe3-wildcard-pw-type-00.txt January 2006
Expiration Date
July 2006
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