IMS ICSCF 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. route_lir_user_unknown (string)
              3.2. route_uar_user_unknown (string)
              3.3. scscf_entry_expiry (integer)
              3.4. cxdx_forced_peer (string)
              3.5. cxdx_dest_realm (string)
              3.6. use_preferred_scscf_uri (int)
              3.7. preferred_scscf_uri (string)

        4. Functions

              4.1. I_scscf_select(initial)
              4.2. I_scscf_drop()
              4.3. I_perform_user_authorization_request(route_block,
                      capabalities)

              4.4. I_perform_location_information_request(route_block)

        5. Statistics

              5.1. Average UAR Response Time (uar_avg_response_time)
              5.2. UAR Timeouts (uar_timeouts)
              5.3. Average LIR Response Time (lir_avg_response_time)
              5.4. LIR Timeouts (lir_timeouts)

   List of Examples

   1.1. route_lir_user_unknown parameter usage
   1.2. route_uar_user_unknown parameter usage
   1.3. scscf_entry_expiry parameter usage
   1.4. cxdx_forced_peer parameter usage
   1.5. cxdx_dest_realm parameter usage
   1.6. use_preferred_scscf_uri parameter usage
   1.7. preferred_scscf_uri parameter usage
   1.8. I_scscf_select usage
   1.9. I_scscf_drop usage
   1.10. I_perform_user_authorization_request usage
   1.11. I_perform_location_information_request

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. route_lir_user_unknown (string)
        3.2. route_uar_user_unknown (string)
        3.3. scscf_entry_expiry (integer)
        3.4. cxdx_forced_peer (string)
        3.5. cxdx_dest_realm (string)
        3.6. use_preferred_scscf_uri (int)
        3.7. preferred_scscf_uri (string)

   4. Functions

        4.1. I_scscf_select(initial)
        4.2. I_scscf_drop()
        4.3. I_perform_user_authorization_request(route_block,
                capabalities)

        4.4. I_perform_location_information_request(route_block)

   5. Statistics

        5.1. Average UAR Response Time (uar_avg_response_time)
        5.2. UAR Timeouts (uar_timeouts)
        5.3. Average LIR Response Time (lir_avg_response_time)
        5.4. LIR Timeouts (lir_timeouts)

1. Overview

   This module provides all functionality to build an IMS ICSCF.

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
     * SL - Stateless Reply
     * CDP - C Diameter Peer
     * CDP_AVP - CDP AVP Applications

2.2. External Libraries or Applications

   This modules requires the Kamailio internal IMS library.

3. Parameters

   3.1. route_lir_user_unknown (string)
   3.2. route_uar_user_unknown (string)
   3.3. scscf_entry_expiry (integer)
   3.4. cxdx_forced_peer (string)
   3.5. cxdx_dest_realm (string)
   3.6. use_preferred_scscf_uri (int)
   3.7. preferred_scscf_uri (string)

3.1. route_lir_user_unknown (string)

   This is the route which is executed if HSS returns "user unknown" in
   LIR

   Default value is ''.

   Example 1.1. route_lir_user_unknown parameter usage
...
modparam("ims_icscf","route_lir_user_unknown", "lir_term_user_unknown")
...

3.2. route_uar_user_unknown (string)

   This is the route which is executed if HSS returns "user unknown" in
   UAR.

   Default value is ''.

   Example 1.2. route_uar_user_unknown parameter usage
...
modparam("ims_icscf","route_uar_user_unknown", "uar_term_user_unknown")
...

3.3. scscf_entry_expiry (integer)

   This is the time in s after which S-CSCF entries in the I-CSCF's SCSCF
   list will expire.

   Default value is 300.

   Example 1.3. scscf_entry_expiry parameter usage
...
modparam("ims_icscf","scscf_entry_expiry", 300)
...

3.4. cxdx_forced_peer (string)

   FQDN of Diameter Peer (HSS) to use for communication (UAR, LIR). If you
   use this, the routing defined in your diameter xml configuration file
   (CDP) will be ignored and as a result you will lose the benefits of
   load balancing and failover.

   Default value is "".

   Example 1.4. cxdx_forced_peer parameter usage
...
modparam("ims_icscf", "cxdx_forced_peer", "hss.ims.smilecoms.com")
...

3.5. cxdx_dest_realm (string)

   Destination realm to be used in Diameter messags to HSS

   Default value is "ims.smilecoms.com".

   Example 1.5. cxdx_dest_realm parameter usage
...
modparam("ims_icscf", "cxdx_dest_realm", "ims.smilecoms.com")
...

3.6. use_preferred_scscf_uri (int)

   Whether or not this ICSCF has a preferred S-CSCF to use when the HSS
   returns a list of SCSCFs. 0 means this I-CSCF has no preferred SCSCF. 1
   means it has a preferred S-CSCF.

   Default value is 0.

   Example 1.6. use_preferred_scscf_uri parameter usage
...
modparam("ims_icscf", "use_preferred_scscf_uri", 1)
...

3.7. preferred_scscf_uri (string)

   If use_preferred_scscf_uri is set then this is the URI of the preferred
   SCSCF.

   Default value is "".

   Example 1.7. preferred_scscf_uri parameter usage
...
modparam("ims_icscf", "preferred_scscf_uri", "sip:scscf.ims.smilecoms.com:6060")
...

4. Functions

   4.1. I_scscf_select(initial)
   4.2. I_scscf_drop()
   4.3. I_perform_user_authorization_request(route_block, capabalities)
   4.4. I_perform_location_information_request(route_block)

4.1. I_scscf_select(initial)

   This function is used to retrieve the next unused SCSCF from thelist
   for this request (based on callid).

   A positive return code (1) means an SCSCF was found and is armed for
   routing.

   Meaning of the parameters is as follows:
     * initial - Signal whether or not this is an original or subsequent.

   This function can be used from REQUEST_ROUTE | FAILURE_ROUTE.

   Example 1.8. I_scscf_select usage
...
if (I_scscf_select("0")) {
     #there is an S-CSCF list - no need to do a UAR
     t_on_reply("register_reply");
     t_on_failure("register_failure");
     t_relay();
}
...

4.2. I_scscf_drop()

   Drop the list of SCSCFs for this request (based on callid).

   This function can be used from REQUEST_ROUTE | FAILURE_ROUTE |
   REPLY_ROUTE

   Example 1.9. I_scscf_drop usage
...
I_scscf_drop();
...

   .

4.3. I_perform_user_authorization_request(route_block, capabalities)

   Perform a UAR on Diameter CXDX interface. This function will build a
   list of SCSCFs to be used and populate the SCSCF list for the request.
   On a succesful return of this message you can get the next available
   SCSCF by using the I_scscf_select functoin in 4.1.
     * Route block to resume after async UAR Diameter reply.
     * capabilities - whether to request capabilities or not "1" - with
       capabilities, "0" - no capabilities.

   This function can be used from REQUEST_ROUTE.

   p.s. this is executed asynchronously. See example on how to retrieve
   return value

   Example 1.10. I_perform_user_authorization_request usage
...
I_perform_user_authorization_request("REG_UAR_REPLY","0"); #0=REG/DEREG; 1=REG+C
apabilities
exit;
...
route[REG_UAR_REPLY]
{
    #this is async so to know status we have to check the reply avp
    switch ($avp(s:uaa_return_code)){
            case 1: #success
                    if (I_scscf_select("0")){
                            t_on_failure("register_failure");
                            t_on_reply("register_reply");
                            #now relay to appropriate SCSCF
                            if (!t_relay()) {
                                    t_reply("500", "Error forwarding to SCSCF");
                            }
                    } else {#select failed
                            I_scscf_drop();
                            t_reply("500", "Server error on SCSCF Select (UAR)")
;
                    }
                    break;
            case -1: #failure
                    xlog("L_ERR", "UAR failure - error response sent from module
\n");
                    break;
            case -2: #error
                    xlog("L_ERR", "UAR error - sending error response now\n");
                    t_reply("500", "UAR failed");
                    break;
            default:
                    xlog("L_ERR", "Unknown return code from UAR, value is [$avp(
s:uaa_return_code)]\n");
                    t_reply("500", "Unknown response code from UAR");
                    break;
    }
}
...

4.4. I_perform_location_information_request(route_block)

   Perform a LIR on Diameter CXDX interface.
     * Route block to resume after async LIR Diameter reply.

   This function can be used from REQUEST_ROUTE.

   p.s. this is executed asynchronously. See example on how to retrieve
   return value

   Example 1.11. I_perform_location_information_request
...
I_perform_location_information_request("SESSION_LIR_REPLY","0");
exit;
...
route[SESSION_LIR_REPLY]
{
    if ($avp(lia_return_code) == 1) {
            if (I_scscf_select("0")) {
                    append_branch();
                    t_on_reply("initial_request_reply");
                    t_on_failure("initial_request_failure");
                    if (!t_relay()) {
                            t_reply("500","Error forwarding towards S-CSCF");
                            break;
                    }
                    break;
            } else {
                    xlog("L_DBG", "dropping scscf list on initial request\n");
                    I_scscf_drop();
                    t_reply("500", "Server error on LIR select S-CSCF");
                    break;
            }
    } else {
            t_reply("500", "Server error on LIR");
            break;
    }
    break;
}
...

5. Statistics

   5.1. Average UAR Response Time (uar_avg_response_time)
   5.2. UAR Timeouts (uar_timeouts)
   5.3. Average LIR Response Time (lir_avg_response_time)
   5.4. LIR Timeouts (lir_timeouts)

5.1. Average UAR Response Time (uar_avg_response_time)

   The average response time in milliseconds for UAR-UAA transaction.

5.2. UAR Timeouts (uar_timeouts)

   The number of UAR timeouts.

5.3. Average LIR Response Time (lir_avg_response_time)

   The average response time in milliseconds for LIR-LIA transaction.

5.4. LIR Timeouts (lir_timeouts)

   The number of LIR timeouts.