Page 490 7750 SR OS Services Guide
BGP VPLS
The Alcatel-Lucent BGP VPLS solution, compliant with RFC 4761, is described in this section.
Figure 79: BGP VPLS Solution
Figure 79 depicts the service representation for BGP VPLS mesh. The major BGP VPLS
components and the deltas from LDP VPLS with BGP AD are explained below:
• Data plane is identical with the LDP VPLS solution: for example, VPLS instances
interconnected via pseudowire mesh. Split horizon groups may be used for loop avoidance
between pseudowires.
• Addressing is based on two (2) bytes VE ID assigned to the VPLS instance.
→ BGP-AD for LDP VPLS: 4 bytes VSI-ID (system IP) identifies the VPLS instance.
• The target VPLS instance is identified by the Route Target (RT) contained in the MP-BGP
advertisement (extended community attribute).
→ BGP-AD: a new MP-BGP extended community is used to identify the VPLS. RT is
used for topology control.
• Auto-discovery is MP-BGP based. Same AFI, SAFI used as for LDP VPLS BGP-AD.
→ The BGP VPLS updates are distinguished from the BGP-AD ones based on the value
of the NLRI prefix length: 17 bytes for BGP VPLS, 12 bytes for BGP-AD
→ BGP-AD NLRI is shorter since there is no need to carry pseudowire label information
as T-LDP does the pseudowire signaling for LDP VPLS
• Pseudowire label signaling is MP-BGP based. As a result the BGP NLRI content includes
also label related information – for example, block offset, block size and label base.
→ LDP VPLS: target LDP (T-LDP) is used for signaling the pseudowire service label.
→ The L2 extended community proposed in RFC 4761 is used to signal pseudowire
characteristics – for example, VPLS status, control word, sequencing
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