A first optical interface is coupled to a first IP service node and a
first non-IP service node. A second optical interface is coupled to a
second IP service node and a second non-IP service node. The first
optical interface is coupled to the second optical interface by a first
working link for the IP service nodes and by a second working link for
the non-IP service nodes. The first optical interface is coupled to the
second optical interface by a shared protect link. The first optical
interface and the second optical interface replace either of the first
working link or the second working link with the shared protect link.