Virtual Private LAN Service224FD 100/320Gbps NT and FX NT IHub Services Guide3HH-11985-AAAA-TQZZA Issue: 13Each of the FEC fields are designed as a sub-TLV equipped with its own type andlength providing support for new applications. To accommodate the BGP ADinformation model the following FEC formats are used:• AGI (type 1) is identical in format and content with the BGP extended communityattribute used to carry the VPLS-ID value.• Source All (type 1) is a 4 bytes value destined to carry the local VSI-ID (outgoingNLRI minus the RD).• Target All (type 1) is a 4 bytes value destined to carry the remote VSI-ID (incomingNLRI minus the RD).5.10.3 BGP-AD and Target LDP (T-LDP) InteractionBGP is responsible for discovering the location of VSIs that share the same VPLSmembership. LDP protocol is responsible for setting up the pseudowire infrastructurebetween the related VSIs by exchanging service specific labels between them.Once the local VPLS information is provisioned in the local PE, the related PEsparticipating in the same VPLS are identified through BGP AD exchanges. A list offar end PEs is generated and will trigger the creation, if required, of the necessaryT-LDP sessions to these PEs and the exchange of the service specific VPN labels.The steps for the BGP AD discovery process and LDP session establishment andlabel exchange are shown in Figure 28.AII Type Length ValueSAII Value (continued)AII Type Length ValueTAII Value (continued)(2 of 2)
