Nokia 7330 - Table 110 BGP AD NLRI Versus IP VPN NLRI; Table 111 Generalized Pseudowire-ID FEC Element; FEC Element for T-LDP Signaling

FD 100/320Gbps NT and FX NT IHub Services Guide Virtual Private LAN Service
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Table 110 BGP AD NLRI versus IP VPN NLRI
Network Layer Reachability Information (NLRI) is exchanged between BGP peers
indicating how to reach prefixes. The NLRI is used in the Layer 2 VPN case to tell PE
peers how to reach the VSI rather than specific prefixes. The advertisement includes
the BGP next hop and a route target (RT). The BGP next hop indicates the VSI
location and is used in the next step to determine which signaling session is used for
pseudowire signaling. The RT, also coded as an extended community, can be used
to build a VPLS full mesh.
BGP is only used to discover VPN endpoints and the corresponding far end PEs. It
is not used to signal the pseudowire labels. This task remains the responsibility of
targeted-LDP (T-LDP).
5.10.2 FEC Element for T-LDP Signaling
Two LDP FEC elements are defined in RFC 4447, PW Setup & Maintenance Using
LDP. The original pseudowire-ID FEC element 128 (0x80) employs a 32-bit field to
identify the virtual circuit ID and it was used extensively in the initial VPWS and VPLS
deployments. The simple format is easy to understand but it does not provide the
required information model for BGP AD function. In order to support BGP AD and
other new applications a new Layer 2 FEC element, the generalized FEC (0x81) is
required.
The generalized pseudowire-ID FEC element has been designed for auto discovery
applications. It provides a field, the address group identifier (AGI), that is used to
signal the membership information from the VPLS-ID. Separate address fields are
provided for the source and target address associated with the VPLS endpoints
called the Source Attachment Individual Identifier (SAII) and respectively, Target
Attachment Individual Identifier (TAII). These fields carry the VSI ID values for the
two instances that are to be connected through the signaled pseudowire. The
detailed format for FEC 129 is represented in Table 111.
Table 111 Generalized Pseudowire-ID FEC Element
BGP AD NLRI Usage IP VPN NLRI Usage
Route Distinguisher (8 Octets) Route Distinguisher (8
Octets)
VSI id (4) (IP Prefix) IP Prefix
0123
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Gen PWid (0x81) |C| PW Type PW info Length
AGI Type Length Value
AGI Value (continued)
(1 of 2)