Juniper JUNOSE SOFTWARE FOR E SERIES 11.0.X - BGP AND MPLS CONFIGURATION GUIDE 2009-12-30 Configuration Manual page 610

JUNOSe 11.0.x BGP and MPLS Configuration Guide
for a local PE router is equal to the total number of other PE routers that participate
in the VPLS instances configured on the local PE router. As is the case with Martini
encapsulation for Ethernet layer 2 services over MPLS, a targeted session to a remote
PE router can have many pseudowires that terminate at the same remote PE router.
To enable LDP to establish targeted sessions with remote PEs across the MPLS core,
you must issue both the mpls ldp vpls-id command to configure a VPLS identifier
for the VPLS instance, and the mpls ldp vpls neighbor command to configure a list
of neighbor (peer) addresses to which LDP can send or from which LDP can receive
targeted hello messages.
PWid FEC Element TLV
LDP signaling information for VPLS is carried in a label mapping message. The label
mapping message contains the Generic Label type-length-value (TLV), and the
pseudowire identifier (PWid) forwarding equivalence class (FEC) element. A FEC is
a group of IP packets forwarded over the same path with the same path attributes
applied.
The PWid FEC element (FEC Type 128 or 0x80) contains the VPLS identifier
information configured for your VPLS instance with the mpls ldp vpls-id command.
Taken together, the pseudowire type field and the PWid field in the TLV represent a
unique VPLS instance. The pseudowire type field is Ethernet to identify the
pseudowires that carry Ethernet traffic for multipoint connectivity between the local
and remote VEs. The PWid field is a nonzero 32-bit integer that contains the VPLS
identifier, which is a globally unique identifier for a VPLS domain. All VEs that
participate in the same VPLS domain must use the same VPLS identifier.
Martini encapsulation for Ethernet layer 2 services over MPLS also uses the PWid
FEC Element TLV. As a result, the PWid for Martini configurations must not be the
same as the VPLS identifier configured for a VPLS instance. To prevent this conflict
from occurring, the JUNOSe software displays an error and rejects the configuration
if you attempt to configure the same value for the Martini PWid and the VPLS
identifier.
Related Topics
BGP Multihoming for VPLS
BGP multihoming enables you to connect a customer site to two or more PE routers
to provide redundant connectivity while preventing the formation of layer 2 loops
in the service provider's network. The redundant connectivity maintains the VPLS
service and traffic forwarding to and from the multihomed site in the event of a PE
router-to-CE device link failure, the failure of a PE router, or an MPLS reachability
failure between the local PE router and a remote PE router. A redundant PE router
can begin providing service to the customer site as soon as the failure is detected.
BGP multihoming is very similar for both VPLS and VPWS, with only minor differences
in behavior between the two L2VPN types.
574
BGP Multihoming for VPLS
Configuring LDP Signaling for VPLS on page 601
Configuring MPLS on page 263.