A shared (proxy) OAM session is performed in a packet-based network on behalf of a plurality of connections. First and second connections are each routed between respective nodes of the network for carrying data traffic. The second connection shares a portion of the routing of the first connection. The shared OAM session is performed along a path which is co-routed with at least part of the shared portion of the routing of the first connection and the second connection. Failure notification signalling is propagated to an endpoint node of each of the first and second connections when the shared OAM session indicates a failure has occurred. The use of a shared OAM session reduces processing at nodes and reduces OAM traffic. Each connection can be a trunk, such as a PBT/PBB-TE trunk, or a service carried within a trunk.