Abstract: Whenever a call is being established, a call loop may occur if a call server detects that the call is being re-routed back to a destination to which it has already been routed. Call loop is precluded by establishing a list of controlling services into which all re-routing services of parties who may be involved in the call are inserted. Each destination address for each call-leg is first treated as if it is a service address, and then as if it is a routable address. If the destination to which the call is being re-routed is the address of the party who modified the address, the call will proceed; otherwise any one of the following steps is followed: Returning a “busy” or “loop detected” message; treating the destination address as a routable address, and attempting to reach the network element associated with that address; offloading the call to another network element which is capable of resolving a call loop, or to the network element at the destination of the calling party.

Abstract: A call server which permits from zero to multiple call-legs per call also permits multiple services independently of the number of participants in any call being established or already established. A finite state machine logic device is established for each call so as to capture the evolution of the call during its lifetime, and to enable the call server to handle and process signalling messages from endpoints associated with the call and of requests from call services running on the call server during that call. The finite state machine logic device changes state during the progress of a call, in keeping with instructions that it receives as the call evolves. At any time, any service associated with any call-leg of that call may alter the by processing of the call in keeping with predetermined instructions associated with that service. The finite state machine logic device may be associated with the call server, or any call leg established for a call, or both.