Avaya Configuring MPLS Services Manuel d'utilisateur télécharger pdf (Page 20)

Configuring MPLS Services

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305754-A Rev 00

Label Distribution Entity

The label distribution entity is essentially the implementation of the Label

Distribution Protocol (LDP). LDP is the set of procedures and messages by which

label-switching routers (LSRs) establish label-switched paths (LSPs) through a

network. LDP establishes these paths by mapping network layer routing

information directly to data link layer switched paths.

LDP associates a packet stream with a specific LSP and assigns the LSP a specific

label. The label information is distributed between the LSRs and LERs to

maintain stream mapping information.

MPLS Label Management

The MPLS label management (MLM) entity communicates with LDP. It is

responsible for:

• Establishing the default VC

• Responding to requests from LDP (for example, requests for a label and

establishing VC communications)

• Communicating with the ATM driver to set up and tear down VCs

Forwarding

The forwarding entity encapsulates and decapsulates the data that it sends and

receives over the MPLS interface.

Outbound data is delivered to the encapsulation process by the higher layers and

delivered to the lower-level driver for transmission to the MPLS network.

Inbound data is received from the MPLS network by the lower-level driver and

delivered to the decapsulation process, where it is stripped of layer 2 protocol

headers. The decapsulation process then passes the inbound data to higher layers

for further processing.

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Avaya Configuring MPLS Services Manuel d'utilisateur Page 20