SIP Tunneling

Feature Overview

SIP tunneling is a mechanism that transports any kind of data using SIP signaling messages.

The CSP SIP stack now supports tunneling with the host playing an important role.

The SIP stack acts as a "black box" and the host determines what data to tunnel and what format to transport.

Important! SIP tunneling is a proprietary feature that works between CSP's only.

Refer to Description for a detailed explanation of this feature.

Pertinent Specifications

RFC 3398 - ISUP to SIP Mapping

RFC 3261 - SIP

RFC 3666 - SIP PSTN Call Flows

RFC 2046 - MIME Part Two: Media Types

Benefits to Customer

Transporting PSTN signaling through IP is one use case of SIP Tunneling.

The following process tunnels SS7 messages through IP.


1. The CSP reports the IAM from the network to the host as SS7 ICBs within the Request for Service with Data (0x002D) message.

2. The received ICBs are provided to the SIP stack using the Outseize Control or Route Control API messages and Subsequent PPL Event Request (0x023). The message is embedded within the SIP INVITE message as MIME data and sent through the IP network.

3. The CSP UAC receiving the SIP INVITE message reports the MIME data to the host with the RFS.

4. The host can use this SS7 ICB received from the INVITE message to make an outbound SS7 call with appropriate parameters.

Similarly for other SS7 messages, a SIP message is used to tunnel it through the IP network.

There is not hardwired nor one-to-one mapping of SS7 messages to SIP message. Refer to Recommended mapping between ISUP messages and SIP messages.

API and TLVs


Outseize Control (0x002C)

Request for Service (0x002D)

Route Control (0x00E8)

PPL Event Request (0x0044)

PPL Event Indication (0x0043)

Release Channel with Data (0x36)

Connect with Data (0x05)

Channel Released with Data (0x69)


0x2964 SIP MIME Information

Call Flow

PPL Information

PPL Event Request 0x0022 in PPL Component 0x00A7 generates 181 Call is Being Forwarded

PPL Event Indication in PPL Component 0x00A7 reports the receipt of 181 response.

Call Flows

High-level call flow for ISUP tunneled through SIP