Alcatel-Lucent 7210 SAS M Service Guide

VPLS Features
Page 272 7210 SAS M Services Guide
VPLS Redundancy
The VPLS standard (RFC 4762, Virtual Private LAN Services Using LDP Signalling) includes
provisions for hierarchical VPLS, using point-to-point spoke SDPs. Two applications have been
identified for spoke SDPs:
• To connect to Multi-Tenant Units (MTUs) to PEs in a metro area network;
• To interconnect the VPLS nodes of two networks.
In both applications the spoke SDPs serve to improve the scalability of VPLS. While node
redundancy is implicit in non-hierarchical VPLS services (using a full mesh of SDPs between
PEs), node redundancy for spoke SDPs needs to be provided separately. In VPLS services,only
two spoke-SDPs are allowed in an endpoint.
Alcatel-Lucent routers have implemented special features for improving the resilience of
hierarchical VPLS instances, in both MTU and inter-metro applications.
Spoke SDP Redundancy for Metro Interconnection
When two or more meshed VPLS instances are interconnected by redundant spoke SDPs (as
shown in Figure 42), a loop in the topology results. In order to remove such a loop from the
topology, Spanning Tree Protocol (STP) can be run over the SDPs (links) which form the loop
such that one of the SDPs is blocked. As running STP in each and every VPLS in this topology is
not efficient, the node includes functionality which can associate a number of VPLSes to a single
STP instance running over the redundant-SDPs. Node redundancy is thus achieved by running
STP in one VPLS, and applying the conclusions of this STP to the other VPLS services. The
VPLS instance running STP is referred to as the “management VPLS” or mVPLS.
In the case of a failure of the active node, STP on the management VPLS in the standby node will
change the link states from disabled to active. The standby node will then broadcast a MAC flush
LDP control message in each of the protected VPLS instances, so that the address of the newly
active node can be re-learned by all PEs in the VPLS.
It is possible to configure two management VPLS services, where both VPLS services have
different active spokes (this is achieved by changing the path-cost in STP). By associating
different user VPLSes with the two management VPLS services, load balancing across the spokes
can be achieved.

Alcatel-Lucent 7210 SAS M Specifications

General

Brand	Alcatel-Lucent
Model	7210 SAS M
Category	Switch
Language	English