Page 226 7750 SR OS Services Guide
state according to its local MC-LAG instance and thus advertises active status notification
messages to both its peer pseudowire nodes, for example, nodes C and D. Node D performs the
same operation. Node B is in the standby state according to the status of the SAP in its local MC-
LAG instance and thus advertises standby status notification messages to both nodes C and D.
Node C performs the same operation.
An SR-Series node selects a pseudowire as the active path for forwarding packets when both the
local pseudowire status and the received remote pseudowire status indicate active status. However,
an SR-Series device in standby status according to the SAP in its local MC-LAG instance is
capable of processing packets for a VLL service received over any of the pseudowires which are
up. This is to avoid black holing of user traffic during transitions. The SR-Series standby node
forwards these packets to the active node via the Inter-Chassis Backup pseudowire (ICB
pseudowire) for this VLL service. An ICB is a spoke SDP used by a MC-LAG node to backup a
MC-LAG SAP during transitions. The same ICB can also be used by the peer MC-LAG node to
protect against network failures causing the active pseudowire to go down.
Note that at configuration time, the user specifies a precedence parameter for each of the
pseudowires which are part of the redundancy set as described in the application in VLL
Resilience with Two Destination PE Nodes on page 223. An SR-Series node uses this to select
which pseudowire to forward packet to in case both pseudowires show active/active for the local/
remote status during transitions.
Only VLL service of type Epipe is supported in this application. Furthermore, ICB spoke SDP can
only be added to the SAP side of the VLL cross-connect if the SAP is configured on a MC-LAG
instance.
To Next Page
Loading...
