Traffic loss during port switchover depends on the following factors:
Routing convergence; this depends on the number of routes in the network and the deployed routing protocol.
The time it takes to associate PW SAPs with a new port. This action is performed within the VSR and the timing depends on the number of PW SAPs that are being moved from the old port to the new port. Note that PW SAPs are not recreated, instead the existing PW-SAPs are re-mapped to a new port.
The egress queues on the new port must be recreated. However, this does not incur additional downtime because a spare egress queue is always present on a port (referred to as a failover queue) and is used while per PW SAP egress queues are being created.
Depending on the scale and network load, downtime during a switchover can range from the sub-second range to a several seconds.