Associate PW label with PTP application

[1588overMPLS] defines two methods for transporting PTP messages (PDUs) over an MPLS network. The second method is to transport PTP messages inside a PW via Ethernet encapsulation. When PHP is applied to PTP LSP or the PW is etablished between two routers directly and no PTP LSP is needed, PW label must be associated with PTP application at the PW termination point. This document extend LDP and BGP to associate PW label with PTP application.

It is useful for PW switching point to announce its capabilities, such as the capability to be PTP-aware. So both PW switching points could know each other of the PTP-aware capability. If both of them could support PTP-aware, PTP PW label could be coordinated during the label mapping.

[RFC5561] defines a mechanism for advertising LDP enhancements at session initialization time. So LDP capability advertisement provides means for an LDP speaker to announce what it can receive and process. This document introduces a new Capability Parameter TLV, the PTP-Aware Capability. Following is the format of the PTP-Aware Capability Parameter.

The PTP-Aware Capability TLV MUST be supported in the LDP Initialization Message([RFC5561]). Advertisement of the PTP-Aware Capability indicates that the PW switching point supports PTP message processing and PTP application association

TBD

When PTP LSP isn't be present, PW switching point must associate the top label (aka PW Label) with PTP application so that it can identify PTP traffic carried in the PW. This PTP application association relationship could be configured by management system. It could also be configure by dynamic control plane. This document introduces LDP/BGP extension to signal that this PW segment is a PTP PW.

[RFC3036] defines the Label Distribution Protocol (LDP) for distributing labels. This document defines a new TLV, PTP Association TLV which can be used to indicate a PW is associated with PTP traffic. This TLV is carried in the Label Mapping message. The PTP Association TLV, is defined as follows (TLV type needs to be assigned by IANA):

The OFFSET to the start of the PTP message header MAY also be signaled. Implementations can trivially locate the correctionField (CF) location given this information. The OFFSET points to the start of the PTP header as a node may want to check the PTP messageType before it touches the correctionField (CF). The T-PE or S-PE must include this object in the LDP Mapping Message when it want to request a PTP label or advertise a PTP label to a peer.

TBD

TBD.