rfc-4863

Wildcard Pseudowire Type

L. Martini, G. Swallow

date2007-05 streamIETF areartg wgpwe3 statusPROPOSED STANDARD pages6 canonicalhttps://www.rfc-editor.org/rfc/rfc4863 doi10.17487/RFC4863

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 is needed for allowing the PW endpoint (lacking a priori knowledge of the PW Type) to initiate the creation of an LSP. This document defines a Wildcard PW Type to satisfy this need. [STANDARDS-TRACK]

Extracted elements (7)

design-rationale §1

The Wildcard PW Type was introduced because in LDP-based pseudowire signaling both endpoints must send Label Mapping messages carrying the PW Type, but when an ingress PE acts as a gateway between a layer 2 network and remote PEs, the layer 2 signaling may not contain sufficient information to determine the PW Type. The wildcard allows the uninformed endpoint to initiate its LSP independently, with the far end supplying the actual PW Type.

mpls

interoperability-note §3.2

A targeted PE that receives the wildcard FEC first performs the normal AGI and TAII validation procedures; if it holds a non-wildcard PW Type configuration for the identified attachment, it treats the incoming Label Mapping as if it had specified that configured PW Type. The wildcard is never echoed back as the resolved type.

mpls

normative-requirement §3.1 MUST

When a PE sends a wildcard FEC and receives a Label Mapping response, if the returned PW Type cannot be supported or is itself the wildcard value, the PE MUST respond with a Label Release message carrying an LDP Status Code of 'Generic Misconfiguration Error'.

mpls

normative-requirement §3.2 MUST

When a targeted PE receives a Label Mapping message with the wildcard PW Type and is not configured to use a specific, non-wildcard PW Type, it MUST respond with a Label Release message carrying an LDP Status Code of 'Generic Misconfiguration Error'.

mpls

protocol-element §2

The Wildcard PW Type is defined with codepoint 0x7FFF. It signals to the targeted PE that it should determine the PW Type for both directions and signal that back in a Label Mapping message. For matching purposes it is interpreted to match any PW Type other than itself.

mpls

registry §5

IANA allocated codepoint 0x7FFF with description 'Wildcard' in the 'Pseudowire Type' registry (defined by BCP 116, RFC 4446) from the IETF consensus range.

mpls, registry

security-consideration §4 SHOULD

A pseudowire control entity receiving a wildcard FEC request SHOULD only proceed with setup if explicitly configured to do so for the particular Attachment Identifier in the Target Attachment Identifier, because a malicious agent attempting to connect to an access circuit requires one less piece of information when using the wildcard. Implementations should also follow the security considerations of RFC 4447 for the Generalized PWid FEC Element.

mpls, security