oller that provides routes within the domain of its responsibility. Step-by-step routing requires less routing information in the nodes than the previous methods. In such a case path selec- tion is invoked at each node to obtain the next link on a path to a destination. Convergent Network Management and Control Plane 8.2.3.3 Signaling Signaling protocols are used to create, maintain, restore, and release connections. Such protocols are essential to enable fast provisioning or fast recovery after failures. Signaling network in ASTN should be based on common channel signaling, which involves separa- tion of the signaling network from the transport network. Such a solution supports scal- ability, a high degree of resilience, efficiency in using signaling links, as well as flexibility in extending message sets. A variety of different protocols can interoperate within a multidomain network and the interdomain signaling protocols shall be agnostic to their intradomain counterparts. As a matter of fact, interdomain signaling is managed by the domain interface protocols related to E-NNI interface, which are completely independent of the internal protocols of the domain. 8.2.3.4 Call and Connection Control Call and connection control are separated in the ASON architecture. A call is an asso- ciation between endpoints that supports an instance of service, while a connection is a concatenation of link connections and subnetwork connections (connections crossing the border between nearby administrative domains or routing areas) that allows transport of user information. A call may embody any number of underlying connections, including zero. The call and connection control separation makes also sense for restoration after faults. In such a case, the call can be maintained (i.e., it is not released) while restoration procedures are under- way. The call control must support coordination of connections in a multiconnection call and the coordination of parties in a multiparty call. It is responsible for negotiation of end- to-end