For the purposes of identifying call flows and the corresponding Session Manager and Communication Manager SIP resources involved, the endpoints are consolidated into the following four categories:

• SIP stations

  SIP stations registered to Session Manager, using Communication Manager administered as either a feature server or an evolution server as feature source.

• Non-IMS SIP elements

  Non-SIP endpoints on a Communication Manager administered as an evolution server, endpoints on non-Avaya SIP gateways, SIP service providers, SIP voice portals, and Messaging

• Non-SIP Communication Manager

  Endpoints on non-SIP-enabled Communication Manager

• Non-SIP PSTN trunks

  Endpoints in the PSTN that are connected to Session Manager via non-SIP trunking (the case of SIP trunking is covered in non-IMS SIP elements)

The call flows associated with the various combinations of the preceding endpoint types are described in more detail in the examples.