Virtual Leased Line Services
7210 SAS M Services Guide Page 145
Pseudowire Redundancy
Pseudowire redundancy provides the ability to protect a pseudowire with a pre-provisioned
pseudowire and to switch traffic over to the secondary standby pseudowire in case of a SAP and/or
network failure condition. Normally, pseudowires are redundant by the virtue of the SDP
redundancy mechanism. For instance, if the SDP is an RSVP LSP and is protected by a secondary
standby path and/or by Fast-Reroute paths, the pseudowire is also protected. However, there are a
couple of applications in which SDP redundancy does not protect the end-to-end pseudowire path:
• There are two different destination PE nodes for the same VLL service. The main use case
is the provision of dual-homing of a CPE or access node to two PE nodes located in
different POPs. The other use case is the provision of a pair of active and standby BRAS
nodes, or active and standby links to the same BRAS node, to provide service resiliency to
broadband service subscribers.
• The pseudowire path is switched in the middle of the network and the SR-Series
pseudowire switching node fails.
Pseudowire and VPLS link redundancy extends link-level resiliency for pseudowires and VPLS to
protect critical network paths against physical link or node failures. These innovations enable the
virtualization of redundant paths across the metro or core IP network to provide seamless and
transparent fail-over for point-to-point and multi-point connections and services. When deployed
with multi-chassis LAG, the path for return traffic is maintained through the pseudowire or VPLS
switchover, which enables carriers to deliver “always on” services across their IP/MPLS networks.
Figure 23: VLL Resilience
If the Ethernet SAP on PE2 fails, PE2 notifies PE1 of the failure by either withdrawing the
primary pseudowire label it advertised or by sending a pseudowire status notification with the
code set to indicate a SAP defect. PE1 will receive it and will immediately switch its local SAP to
IP/MPLS
7750 SR
PE 2
PE 3
PE 1
Eth SAP
Eth SAP
(standby)
Eth SAP
(primary)
Primary Eth
Standby
backup Eth
PW
DSLAM
BRAS 1
7210 SAS
7750 SR
OSSG115-7210M
To Next Page
Loading...
