Packet1 Edge soft switch complements the Mobilis Home Subscriber Server. The Packet1 Edge soft switch is responsible for maintaining the connection to the subscriber’s end point over packet networks. The endpoint is a SIP compatible hard or soft device. In the future IMS-SIP compatible devices will be more readily available as carriers begin to implement LTE wireless networks.

Packet1 Edge Call Session Control is made up of three call session control functions. These functions act as SIP proxies channeling requests between the endpoints, application servers and external networks.

Proxy Call Session Control Function is a SIP proxy that is the first contact point for the user’s device. It can be located on the visited network when that network is IMS compliant or co-located on the home network when the visited network is not IMS compliant. It includes a Policy Decision Function (PDF) and Session Border Control (SBC), which authorizes media plane resources like quality of service (QoS) over the media plane. It is used for policy control, bandwidth management and enables the application layer to be access network agnostic. It inspects all messages and provides the information required for the CDRs.

Interrogating Call Session Control Function is a SIP proxy that is located in the home network and determines the S-CSCF that the user should be registered with in conjunction with an M-HSS. When a user initiates a call it will setup the call in the receiving party’s network so the receiving party’s S-CSCF can be resolved.

Serving Call Session Control Function is a SIP server that is the control point for registering users; it also controls services delivered to the registered users. It determines where SIP Application Server(s) messages should be forwarded and it enforces network policies. It sits on the path for all Signalling messages and can therefore inspect all messages. Finally it communicates with the Packet1 Identity to determine user authorizations, service triggering and profile information.