Interworking with CS | Nortel Networks NN10033-111 manual

Nortel Networks Confidential	Overview 5

•SIP/PRI mapping support, including:

—Protocol parameter mapping

—error codes

—PRI cause values with SIP responses

—presentation and screening indicators

•PRACK: the provisional response acknowledge message that ensures that the ringing signal does not get lost.

•Type of Server (ToS): The ToS bit can be configured to indicate the priority of the voice packet over data packet to ensure quality of service.

•Long-call service: The ability to detect abandoned calls.

More detailed information about the functional capabilities of the SIP PRI Gateway is available in the MCP SIP PRI Gateway Basics document.

Interworking with CS 2000

Even though Nortel Networks Communication Server 2000 (CS 2000) is a VoIP switch, it does not fully support the Session Initiation Protocol (SIP). The following description provides information on how the MCP interworks with the CS 2000.

The MCP does not support VoIP over Asynchronous Transfer Mode (ATM) or pure ATM, as the MCP network nodes are IP-based and not ATM based.

Functional description

The interworking between an MCP and CS 2000 uses Session Initiation Protocol for Telephones (SIP-T) over User Datagram Protocol (UDP) to transport ISDN User Part (ISUP), the call control part of the Signaling System 7 (SS7) protocol.

SIP-T is an extension of the Session Initiation Protocol (SIP) that allows SIP to be used to facilitate the interconnection of the Public Switched Telephone Network (PSTN) with packet networks. SIP-T encapsulates the ISDN User Part (ISUP) messages in the SIP messages and translates ISUP information into the SIP header for routing purposes.

Although the MCP SIP Application Module supports receiving of encapsulated ISUP messaging (using SIP-T), it does not send encapsulated ISUP back out. For more information about the capabilities of the SIP Application Module, please refer to the SIP Application Module Basics document.

MCP Interworking Basics