The IMS ISC Module

Dragos Vingarzan

   FhG Fokus
   <Dragos.Vingarzan@fokus.fraunhofer.de>

Jason Penton

   Smile Communications
   <jason.penton@smilecoms.com>

Richard Good

   Smile Communications
   <richard.good@smilecoms.com>

   Copyright © 2007 FhG FOKUS

   Copyright © 2012 Smile Communications
     __________________________________________________________________

   Table of Contents

   1. Admin Guide

        1. Overview
        2. Dependencies

              2.1. Kamailio Modules
              2.2. External Libraries or Applications

        3. Parameters

              3.1. my_uri (string)
              3.2. expires_grace (integer)
              3.3. isc_fr_timeout (integer)
              3.4. isc_fr_inv_timeout (integer)
              3.5. add_p_served_user (integer)

        4. Functions

              4.1. isc_match_filter_reg(reg_state,domain)
              4.2. isc_match_filter(direction,domain)
              4.3. isc_from_as(direction)

   List of Examples

   1.1. my_uri parameter usage
   1.2. expires_grace parameter usage
   1.3. isc_fr_timeout parameter usage
   1.4. isc_fr_inv_timeout parameter usage
   1.5. add_p_served_user parameter usage
   1.6. isc_match_filter_reg usage
   1.7. isc_match_filter usage
   1.8. isc_from_as usage

Chapter 1. Admin Guide

   Table of Contents

   1. Overview
   2. Dependencies

        2.1. Kamailio Modules
        2.2. External Libraries or Applications

   3. Parameters

        3.1. my_uri (string)
        3.2. expires_grace (integer)
        3.3. isc_fr_timeout (integer)
        3.4. isc_fr_inv_timeout (integer)
        3.5. add_p_served_user (integer)

   4. Functions

        4.1. isc_match_filter_reg(reg_state,domain)
        4.2. isc_match_filter(direction,domain)
        4.3. isc_from_as(direction)

1. Overview

   This module provides the functionality for an IMS S-CSCF to implement
   the ISC interface between S-CSCF and SIP Application Server.

2. Dependencies

   2.1. Kamailio Modules
   2.2. External Libraries or Applications

2.1. Kamailio Modules

   The Following modules must be loaded before this module:
     * TM - Transaction Manager
     * IMS Usrloc SCSCF

2.2. External Libraries or Applications

   This module requires the Kamailio internal IMS library.

3. Parameters

   3.1. my_uri (string)
   3.2. expires_grace (integer)
   3.3. isc_fr_timeout (integer)
   3.4. isc_fr_inv_timeout (integer)
   3.5. add_p_served_user (integer)

3.1. my_uri (string)

   This is the SIP URI of server on which the SCSCF is hosted.

   Default value is 'sip:scscf.ims.smilecoms.com:6060'.

   Example 1.1. my_uri parameter usage
...
modparam("ims_isc", "my_uri", "sip:scscf.ims.smilecoms.com:6060")
...

3.2. expires_grace (integer)

   This is the expires value to add to the expires during 3rd party
   registration to prevent expiration in Application Server.

   Default value is 120.

   Example 1.2. expires_grace parameter usage
...
modparam("ims_isc", "expires_grace", 120)
...

3.3. isc_fr_timeout (integer)

   This is the time in ms that we will wait for an AS response before we
   consider it dead. It has to be lower than the SIP transaction timeout
   to prevent downstream timeouts. But not too small as ASs tend to take a
   long time to respond.

   Default value is 5000.

   Example 1.3. isc_fr_timeout parameter usage
...
modparam("ims_isc", "isc_fr_timeout", 5000)
...

3.4. isc_fr_inv_timeout (integer)

   This is the time in ms that we will wait for an AS INVITE response
   before we consider it dead. It has to be lower than the SIP transaction
   timeout to prevent downstream timeouts. But not too small as ASs tend
   to take a long time to respond.

   Default value is 20000

   Example 1.4. isc_fr_inv_timeout parameter usage
...
modparam("ims_isc", "isc_fr_inv_timeout", 20000)
...

3.5. add_p_served_user (integer)

   This boolean indicates if a P-Served-User should be added on the ISC
   interface, according to RFC 5502.

   Default value is 0 (false)

   Example 1.5. add_p_served_user parameter usage
...
modparam("ims_isc", "add_p_served_user", 1)
# p-served user header will be enabled
...

4. Functions

   4.1. isc_match_filter_reg(reg_state,domain)
   4.2. isc_match_filter(direction,domain)
   4.3. isc_from_as(direction)

4.1. isc_match_filter_reg(reg_state,domain)

   This function checks if a REGISTER messages matches Initial Filter
   Criteria - if so it inserts the necessary route headers and modifies
   the destination URI to forward to the relevant Application Server.

   A positive return code (1) means that the REGISTER message has matched
   to Initial Filter Criteria and is armed for routing.

   This function handles also the Service Info (if sent by the HSS), the
   InsertRegisterRequest flag (if sent by the HSS) or the
   InsertRegisterResponse flag (if sent by the HSS). Either the Service
   Info OR the original REGISTER request OR the original REGISTER response
   is added to the body of the REGISTER message, before it is forwarded to
   the relevant Application Server. Multipart body is not supported in
   this case.

   Meaning of the parameters is as follows:
     * reg_state if the user was previously registered 0 - for initial
       registration, 1 for re/de-registration.
     * domain that usrloc_scscf uses to store user information.

   This function can be used from REQUEST_ROUTE.

   Example 1.6. isc_match_filter_reg usage
...
isc_match_filter_reg("1","location");
...

4.2. isc_match_filter(direction,domain)

   This function checks if a non-REGISTER messages matches Initial Filter
   Criteria - if so it inserts the necessary route headers and modifies
   the destination URI to forward to the relevant Application Server.

   A positive return code (1) means that the message has matched to
   Initial Filter Criteria and is armed for routing.

   Meaning of the parameters is as follows:
     * direction the direction of this message - orig, term, etc.
     * domain that usrloc_scscf uses to store user information.

   This function can be used from REQUEST_ROUTE | FAILURE_ROUTE.

   Example 1.7. isc_match_filter usage
...
isc_match_filter("orig","location");
...

4.3. isc_from_as(direction)

   This function checks if this message has come from an Application
   Server.

   A positive return code (1) means that the message has come from an
   Application Server.

   Meaning of the parameters is as follows:
     * direction the direction of this message - orig, term, etc.

   This function can be used from REQUEST_ROUTE | FAILURE_ROUTE.

   Example 1.8. isc_from_as usage
...
if (!isc_from_as("orig")) {
    remove_hf("P-Asserted-Identity");
}
...
