Nokia 7302 - Pseudowire Signaling Details

Virtual Private LAN Service
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FD 100/320Gbps NT and FX NT IHub Services Guide
3HH-11985-AAAA-TQZZA Issue: 13
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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.
5.11.1 Pseudowire Signaling Details
The pseudowire is setup using the following NLRI fields:
• VE Block offset (VBO) — used to define for each VE-ID set the NLRI is targeted
• VBO = n*VBS+1; for VBS=8 this results in 1, 9, 17, 25...
• Targeted Remote VE-IDs are from VBO to (VBO + VBS -1)
• VE Block size (VBS) — defines how many contiguous pseudowire labels are
reserved starting with the Label Base
• Nokia implementation always uses a value of eight
• Label Base (LB) — local allocated label base
• The next eight labels are allocated for remote PEs
Thjs BGP update communicates to the other PE(s) to accept the RT in order to reach
(VE-ID=x), use a pseudowire label of LB + VE-ID—VBO using the BGP NLRI for
which VBO=<local VE-ID<VBO + VBS.
Here is an example of how this algorithm works assuming PE1 has VE-ID 7
configured:
• PE1 founds a Label Block of eight (8) consecutive labels available, starting with
LB = 1000.
• PE1 then starts sending BGP Update with pseudowire information of (VBO = 1,
VBS=8, LB=1000) in the NLRI.
• This pseudowire information will be accepted by all participating PEs with VE-IDs
from one (1) to eight (8).
• Each of the receiving PEs will use the pseudowire label = LB +VE-ID-VBO to send
traffic back to the originator PE. For example VE-ID 2 will use pseudowire label
1001.