Virtual Private LAN Service222FD 100/320Gbps NT and FX NT IHub Services Guide3HH-11985-AAAA-TQZZA Issue: 135.10.1 BGP AD OverviewThe BGP protocol establishes neighbor relationships between configured peers. Anopen message is sent after the completion of the three-way TCP handshake. Thisopen message contains information about the BGP peer sending the message. Thismessage contains Autonomous System Number (ASN), BGP version, timerinformation and operational parameters, including capabilities. The capabilities of apeer are exchanged using two numerical values: the Address Family Identifier (AFI)and Subsequent Address Family Identifier (SAFI). These numbers are allocated bythe Internet Assigned Numbers Authority (IANA). BGP AD uses AFI 65 (L2VPN) andSAFI 25 (BGP VPLS).The complete list of allocations may be found at:http://www.iana.org/assignments/address-family-numbersThe complete details about SAFI may be found at:http://www.iana.org/assignments/safi-namespace5.10.1.1 Information ModelFollowing the establishment of the peer relationship, the discovery process beginsas soon as a new VPLS service instance is provisioned on the PE.Two VPLS identifiers are used to indicate the VPLS membership and the individualVPLS instance:• VPLS ID — Membership information, unique network wide identifier; same valueassigned for all VPLS switch instances (VSIs) belonging to the same VPLS;encodable and carried as a BGP extended community in one of the followingformats:• a two-octet AS specific extended community• an IPv4 address specific extended community• VSI-ID — The unique identifier for each individual VSI, built by concatenating aroute distinguisher (RD) with a 4 bytes identifier (usually the system IP of theVPLS PE); encoded and carried in the corresponding BGP NLRI.In order to advertise this information, BGP AD employs a simplified version of theBGP VPLS NLRI where just the RD and the next 4 bytes are used to identify theVPLS instance. There is no need for Label Block and Label Size fields as T-LDP willtake care of signaling the service labels later on.The format of the BGP AD NLRI is very similar with the one used for IP VPN asdepicted in Table 110. The system IP maybe used for the last 4 bytes of the VSI IDfurther simplifying the addressing and the provisioning process.
