SS7 Tunneled Through SIP with Host Interaction


The data tunneled through SIP is CSP specific data, for example SS7 ICBs.

Important! This feature is valid only if the end-to-end SIP communication is between two CSPs.

Figure 5-16 Network Diagram

Note the following regarding this feature:

• The host application must make sure the variant of inbound PSTN stack matches with the variant on the terminating side or at least is compatible.

• The CSP provides provisions to the host to insert the variant type in SIP messages but the CSP cannot validate it.

• The SIP tunneling capability in the CSP cannot always make the CSP interoperable with third party systems using the SIP interface. The data must be tunneled in a universally accepted format or at least understood by that specific third party system that needs to interwork with the CSP.

Support INFO Message in Call Setup Phase

The CSP supports the INFO message (both generating and receiving) during any phase of the call (setup and/or active) as long as the dialog is established. A dialog is established once the UAS responds to the INVITE with any provisional or 2xx response with a tag value in the To URI.

The 100 Trying response for the INVITE message might not contain a To URI tag value if it is generated from a proxy.

The CSP always inserts the To URI tag value in the 100 Trying response to the INVITE so a dialog gets established in the UAC as soon as it receives 100 Trying.

Support 181 Call is Being Forwarded Response

The following PPL Event Request and PPL Event Indication support the generation and reporting the receipt of 181 provisional response respectively.

• PPL Event Request 0x0022 in SIP UA Component 0x00A7 - allow generation of 181 response.

• PPL Event Indication 0x0030 in SIP component 0x00A7 reports the receipt of 181 response.

Support MIME in SIP Messages

MIME data is a bundle of message body and headers defining the message body. MIME is a general term referring to any data in the message body other than the SDP. MIME supports the following SIP messages in addition to the SDP:

• 180 Ringing

• 181 Call is being forwarded

• 182 Queued

• 183 Session Progress (Supports SDP and MIME)

• 200 OK for INVITE (Supports SDP and MIME)


• Cancel



If the NPDI data is to be reported to the host (within the PPL Event Indication) for the receipt of the following is too big to fit into a single API message, then it is reported to the host as Subsequent PPL Event Indication (Event: 0x0023 Comp: 0x00A7).

• 180 Ringing

• 181 Call is being forwarded

• 182 Queued

• 183 Session Progress

• 200 OK for INVITE

820 bytes is the maximum NPDI data length that can be reported to the host in a single PPL Event Indication. The fragmentation of large NPDI data is not supported when reporting INFO or BYE message.

TLVs to Generate and Report SIP Messages

The API messages used to generate and report these SIP message support the following TLVs within the NPDI Universal ICB (0x0033). Refer to Mapping SIP Messages to API Messages.

• 0x2964 SIP MIME Information - This optional TLV uses the following nested TLVs within itself to define the MIME headers and MIME body.

• SIP Content Type TLV - 0x295D

• SIP Content Encoding TLV - 0x2965

• SIP Content Disposition TLV - 0x2966

• SIP Content Language TLV - 0x2967

• SIP MIME Message Body TLV - 0x2968 - Mandatory TLV for MIME encapsulation. If the message body TLV is absent then the SIP message does not contain any MIME data. Per RFC3261, if the message body is present in a SIP message, then the Content-Type header must be present. For this reason the CSP SIP stack inserts a default value of application/custom if the host provides the Message body TLV but not the Content Type TLV.

The host must ensure that the two SS7 stacks involved in the call are compatible with each other. Because of this, the host can define a token for representing the version of the SS7 stack. This token for the version of the SS7 stack, receiving the inbound call can be communicated to the SIP UAS by inserting it in the Content Type header of the outgoing INVITE message. This version can be used to check for compatibility at the SIP receiving end.

For example the Content-Type header looks like:

Content-Type: application/ISUP; version=ANSI_SS7

Configuring and Querying with API

Configuring Reporting of Receipt of 181 Call

By default, the CSP does not report the receipt of 181 Call is Being Forwarded using the PPL Event Indication (0x0043) message. To enable it, set bit 9 in the Call Flow TLV and send it in VoIP Configuration message (0x00EE).

Configuring Sending MIME

You can configure the CSP to send MIME in outgoing SIP messages two ways. Use the first option to control the tunnel type on a per call basis and the second option to configure at the stack level.

• Set the SIP Tunnel Type TLV (0x2936) to value 0x0004 (Custom MIME Body) in the respective messages:

• PPL Event Request (0x0044)

• Outseize Control (0x002C)

• Route Control (0x00E8)

• Connect with Data (0x05)

• Release Channel with Data (0x36)

• Set the SIP Tunnel Type TLV (0x0270) to value 0x0004 (Custom MIME Body) in the VoIP Protocol message (0x00EE).

Configuring Reporting Income MIME

By default, the CSP does not report the incoming MIME. To enable it, set bit 20 of the SIP Message Information Mask TLV (0x027F) and send it in the VoIP Protocol Configure (0x00EE) message.


Use the VoIP Protocol Query (0x00EF) message to query the following:

• SIP PPL Event Notification Mask value

• Message Information Mask value

• SIP Tunnel Type

Configuring with CSA

Configuring Reporting of Receipt of 181 Call

1 To open the CSP SIP Configuration dialog box, do one of the following:

• Select the CSP Matrix Series 3 Card in the node view. Go to the Configuration menu and select SIP> SIP Configuration.

• Right-click the node view window (outside the card slots) and select SIP Configuration from the menu list.

The dialog box opens showing only the common settings and default values.


2 Click the Show Advanced button. The SIP Configuration, Advanced dialog box opens.

3 Under Call Progress Notification are the following options:

4 Select 181 Received.


Configuring Reporting Income MIME

1 Follow steps 1-2 above to access the SIP Configuration, Advanced dialog box.

2 Under SIP Tunnel Type the following options appear.

3 Select Customer MIME Body.











The following tables provide the mapping supported by this feature.

Table 5-5 Recommended mapping between ISUP messages and SIP messages

ISUP Message

SIP Message

Initial address message (IAM)


Address Complete Message (ACM)

180 Ringing

Call Progress Message (CPG) before receiving ANM



In-band information

Call forward; line busy

Call forward; no reply

Call forward; unconditional

180 Ringing 181 Call Is Being Forwarded/183 Session Progress

180 Ringing

183 Session Progress

183 Session Progress

181 Call is being forwarded

181 Call is being forwarded

181 Call is being forwarded

Answer message (ANM)

200 OK for INVITE

Connect message (CON)

200 OK for INVITE

Call progress message (CPG) after having received ANM


Information Request Message (INR)


Information Message (INF)


Release message (REL)


Release complete message (RLC)



Table 5-6

SIP Message

API (Requests)

API (Indications)

180 Ringing

PPL Event Request - Event 0x00CA L4 CH Component (0x0061)

PPL Event Indication - Event 0x0024 SIP Component (0x00A7)

181 Call is being forwarded

PPL Event Request - Event 0x0022 SIP Component (0x00A7)

PPL Event Indication - Event 0x0030 SIP Comp (0x00A7)

182 Queued

PPL Event Request - Event 0x0026 SIP Component (0x00A7)

PPL Event 0x002E SIP Component (0x00A7)

183 Session Progress

PPL Event Request - Event 0x00CB L4 CH Component (0x0061)

PPL Event Request - Event 0x001F SIP UA Comp (0x00A7)

PPL Event Indication - Event 0x001F SIP Comp (0x00A7)

200 OK for INVITE

PPL Event Request - Event 0x00C9 L4 CH Comp (0x0061)

PPL Event Indication - Event 0x0020 SIP Component (0x00A7)


PPL Event Request - Event 0x0025 SIP Component (0x00A7)

PPL Event Indication - Event 0x002C SIP Component (0x00A7)


Release with Data 0x0036

Channel Released with Data (0x0069)

Mapping SIP Messages to API Messages



0x2964 SIP MIME Information

The following new TLV supports this feature.

Used in:
0x0033 NPDI Universal ICB in:
Route Control message
Outseize Control message
Release Channel with Data
Connect with Data
Channel Released with Data
Request for Service with Data
PPL Event Request message
PPL Event Indication message



0, 1

Tag 0x2964

2, 3

Length Variable (Maximum of 780 bytes)


0x0282 PPL Event Notification Mask

Use the following TLV to configure this feature.

Used in:
VoIP Protocol Configure message
VoIP Protocol Query message



0, 1

Tag 0x0282

2, 3

Length 0x0004


Value[0-3] 32 bit mask with each bit selects specific
PPL Event Indication.

Bit 9 - Report receipt of 181 call