Alcatel-Lucent 7750 SR - LDP Signaling; Figure 93: BGP AD Triggering LDP Functions

Page 576 7750 SR OS Services Guide
LDP Signaling
T-LDP is triggered once the VPN endpoints have been discovered using BGP. The T-LDP
session between the PEs is established when one does not exist. The far-end IP address required
for the T-LDP identification is gleaned from the BGP AD next hop information. The pw-template
and pw-template-bind configuration statements are used to establish the automatic SDP or to map
to the appropriate SDP. The FEC129 content is built using the following values:
• AGI from the locally configured VPLS-ID.
• The SAII from the locally configured VSI-ID.
• The TAII from the VSI-ID contained in the last 4 bytes of the received BGP NLRI.
Figure 93 below shows the different detailed phases of the LDP signaling path, post BGP AD
completion. It also indicates how some fields can be auto generated when they are not specified in
the configuration.
Figure 93: BGP AD Triggering LDP Functions
The first command will display the LDP peering relationships that have been established
(Figure 94). The type of adjacency is displayed in the “Adj Type” column. In this case the type is
“Both” meaning link and targeted sessions have been successfully established.
OSSG245
Automatic SDP
Far-End:1.1.1.6 (BGP Next-hop)
Automatic SDP
Far-End:1.1.1.134 (BGP Next-hop)
pw-template 1
vpls 100 customer 1 create
service-mtu 1478
bgp-ad
vpls-id 65535:100
pw-template-bind 1
no shutdown
pw-template 1
vpls 100 customer 1 create
service-mtu 1478
bgp-ad
vpls-id 65535:100
pw-template-bind 1
no shutdown
PE6
MPLS-id=1.1.1.6/32
PE134
MPLS-id=1.1.1.134/32
FEC 129 Label Exchange
Far-End:1.1.1.6 (BGP Next-hop)
AGI: 65535:100 (VPLS-id)
SAII: 1.1.1.134 (VSI-id)
TAII: 1.1.1.6 (VSI-id from BGP AD)
Label: 131063
FEC 129 Label Exchange
Far-End:1.1.1.134 (BGP Next-hop)
AGI: 65535:100 (VPLS-id)
SAII: 1.1.1.6 (VSI-id)
TAII: 1.1.1.134 (VSI-id from BGP AD)
Label: 131067
1
2
4
65535:100
65535:100
3