What is a service instance?
What does this configuration do?
service instance 1110 ethernet
encapsulation dot1q 421
rewrite ingress tag pop 1 symmetric
service-policy output samsung-downlink-10M <---obviously, a locally-configured sp is refercned on this line...
This configuration was taken off a 7600 router that is playing the role of backhaul aggregator in a mobile broadband environment.
I tried searching for an explanation of service instances, but it seems that the only thing I can find is how to configure one - not what it is or when you would deploy one.