5.6 Tag Distribution Protocol (TDP)

5.6 Tag Distribution Protocol (TDP)

For reasons mentioned in Section 2.3.5 , Tag Switching views piggybacking tag binding information on top of routing protocols as the preferred way of distributing tag binding information. However, because this option may not always be viable, Tag Switching provides its own mechanism to distribute tag binding information: the Tag Distribution Protocol (TDP). In this section we present a short overview of TDP.

A TSR that exchanges routing information with some other TSR also maintains a TDP session with that other TSR in order to exchange tag binding information for the routes that have been constructed from the exchanged routing information.

Information exchanged via TDP consists of a stream of messages, where each message consists of a fixed header, followed by one or more Protocol Information Elements (PIEs). The fixed header consists of the Version field, followed by the Length field, followed by the TDP identifier field. The Version field identifies a specific version of TDP. The Length field specifies the total length of a message. The TDP Identifier field identifies the TSR that sends the message. Each PIE is encoded as a structure, where the Type field defines the semantics of the Value field, and the Length field defines the length of the Value field. All the information carried within a PIE is encoded as as well. Use of the encoding provides flexibility and extensibility to the protocols.

At the time of this writing TDP defines the following PIEs:

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Switching in IP Networks: IP Switching, Tag Switching, & Related Technologies

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5.6 Tag Distribution Protocol (TDP)

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