SS7 Tunneled Through SIP with Host Interaction

Description

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)

BYE

Cancel

INFO

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.

Querying

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.

Mapping

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) | INVITE
Address Complete Message (ACM) | 180 Ringing
Call Progress Message (CPG) before receiving ANM Alerting Progress 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 | INFO
Information Request Message (INR) | INFO
Information Message (INF) | INFO
Release message (REL) | BYE/CANCEL
Release complete message (RLC) | N.A.

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)
INFO | PPL Event Request - Event 0x0025 SIP Component (0x00A7) | PPL Event Indication - Event 0x002C SIP Component (0x00A7)
BYE/Cancel | Release with Data 0x0036 | Channel Released with Data (0x0069)

Mapping SIP Messages to API Messages

TLVs

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 message
PPL Event Request message
PPL Event Indication message

Byte | Description
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

Byte | Description
0, 1 | Tag 0x0282
2, 3 | Length 0x0004
4-7 | Value[0-3] 32 bit mask with each bit selects specific PPL Event Indication. Bit 9 - Report receipt of 181 call

See Signaling System Number Seven.
Session-Initiation Protocol. A signaling protocol used for establishing sessions in an IP network. A session could be a simple, two-way telephone call, or it could be a collaborative multi-media conference session.
A computer, attached to the Excel platform through an RS-232 or Ethernet link, from which you run the telecommunications application that controls the Excel platform.
Public Switched Telephone Network
See Programmable Protocol Language.
A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.
Network Protocol Data Intelligence. Also called Interworking, it is a software product that operates within Excels Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excels call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.
See Information Control Block.
Tag-Length-Value block. A standardized block that allows data to inserted in a standard way into API messages.
See Integrated Services Digital Network User Part.
American National Standards Institute. ANSI administers and coordinates the U.S. voluntary standardization and conformity assessment system for the
telecommunications industry. More details on these standards may be
viewed at www.ansi.org.
Voice over Internet Protocol. The delivery of voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public-switched telephone network (PSTN).
Outgoing call setup during real-time call processing on a specific channel.
See Converged Services Administrator.