IMS Registrar SCSCF Module

Jason Penton

   Smile Communications

Edited by

Richard Good

   Smile Communications

   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. default_expires (int)
              3.2. default_expires_range (int)
              3.3. min_expires (int)
              3.4. max_expires (int)
              3.5. subscription_default_expires (int)
              3.6. subscription_expires_range (int)
              3.7. subscription_min_expires (int)
              3.8. subscription_max_expires (int)
              3.9. user_data_dtd (string)
              3.10. user_data_xsd (string)
              3.11. support_wildcardPSI (int)
              3.12. scscf_name (string)
              3.13. store_profile_dereg (int)
              3.14. cxdx_dest_realm (string)
              3.15. cxdx_forced_peer (string)
              3.16. append_branches (integer)
              3.17. method_filtering (integer)
              3.18. user_data_always (integer)
              3.19. error_reply_code (int)
              3.20. skip_multiple_bindings_on_reg_resp (int)

        4. Functions

              4.1. save(async_reply_route, domain, mode, flags)
              4.2. lookup(domain)
              4.3. lookup_path_to_contact(uri)
              4.4. unregister(domain)
              4.5. assign_server_unreg(aysnc_reply_route, domain,
                      direction)

              4.6. impu_registered(domain)
              4.7. term_impu_registered(domain)
              4.8. reg_fetch_contacts(domain, uri, profile)
              4.9. reg_free_contacts(profile)
              4.10. can_subscribe_to_reg(domain)
              4.11. subscribe_to_reg(domain)
              4.12. can_publish_reg(domain)
              4.13. publish_reg(domain)

        5. RPC Commands

              5.1. regscscf.dereg_impu

        6. Statistics

              6.1. registered contacts
              6.2. impus
              6.3. expired contacts

   2. Frequently Asked Questions

   List of Examples

   1.1. Set default_expires parameter
   1.2. Set default_expires_range parameter
   1.3. Set min_expiresparameter
   1.4. Set max_expiresparameter
   1.5. Set subscription_default_expires parameter
   1.6. Set subscription_expires_range parameter
   1.7. Set subscription_min_expiresparameter
   1.8. Set subscription_max_expiresparameter
   1.9. Set user_data_dtdparameter
   1.10. Set user_data_xsdparameter
   1.11. Set support_wildcardPSIparameter
   1.12. Set scscf_nameparameter
   1.13. Set store_profile_deregparameter
   1.14. Set cxdx_dest_realmparameter
   1.15. Set cxdx_forced_peerparameter
   1.16. Set cxdx_forced_peerparameter
   1.17. Set cxdx_forced_peerparameter
   1.18. Set user_data_alwaysparameter
   1.19. Set error_reply_code parameter
   1.20. Set skip_multiple_bindings_on_reg_resp parameter
   1.21. save usage
   1.22. lookup usage
   1.23. lookup usage
   1.24. unregister usage
   1.25. impu_registered usage
   1.26. term_impu_registered usage
   1.27. reg_fetch_contacts usage
   1.28. reg_free_contacts usage
   1.29. can_subscribe_to_reg usage
   1.30. subscribe_to_reg usage
   1.31. can_publish_reg usage
   1.32. publish_reg 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. default_expires (int)
        3.2. default_expires_range (int)
        3.3. min_expires (int)
        3.4. max_expires (int)
        3.5. subscription_default_expires (int)
        3.6. subscription_expires_range (int)
        3.7. subscription_min_expires (int)
        3.8. subscription_max_expires (int)
        3.9. user_data_dtd (string)
        3.10. user_data_xsd (string)
        3.11. support_wildcardPSI (int)
        3.12. scscf_name (string)
        3.13. store_profile_dereg (int)
        3.14. cxdx_dest_realm (string)
        3.15. cxdx_forced_peer (string)
        3.16. append_branches (integer)
        3.17. method_filtering (integer)
        3.18. user_data_always (integer)
        3.19. error_reply_code (int)
        3.20. skip_multiple_bindings_on_reg_resp (int)

   4. Functions

        4.1. save(async_reply_route, domain, mode, flags)
        4.2. lookup(domain)
        4.3. lookup_path_to_contact(uri)
        4.4. unregister(domain)
        4.5. assign_server_unreg(aysnc_reply_route, domain, direction)
        4.6. impu_registered(domain)
        4.7. term_impu_registered(domain)
        4.8. reg_fetch_contacts(domain, uri, profile)
        4.9. reg_free_contacts(profile)
        4.10. can_subscribe_to_reg(domain)
        4.11. subscribe_to_reg(domain)
        4.12. can_publish_reg(domain)
        4.13. publish_reg(domain)

   5. RPC Commands

        5.1. regscscf.dereg_impu

   6. Statistics

        6.1. registered contacts
        6.2. impus
        6.3. expired contacts

1. Overview

   This module contains REGISTER processing logic for the S-CSCF. The
   'storage engine' of this module is provided by the ims_usrloc_scscf
   module:

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:
     * CDP
     * CDP_AVP
     * TM
     * ims_usrloc_scscf

2.2. External Libraries or Applications

   The following libraries or applications must be installed before
   running Kamailio with this module loaded:
     * LibXML2 - used for parsing the XML Subscription information
       obtained from the HSS (Home Subscriber Server)

3. Parameters

   3.1. default_expires (int)
   3.2. default_expires_range (int)
   3.3. min_expires (int)
   3.4. max_expires (int)
   3.5. subscription_default_expires (int)
   3.6. subscription_expires_range (int)
   3.7. subscription_min_expires (int)
   3.8. subscription_max_expires (int)
   3.9. user_data_dtd (string)
   3.10. user_data_xsd (string)
   3.11. support_wildcardPSI (int)
   3.12. scscf_name (string)
   3.13. store_profile_dereg (int)
   3.14. cxdx_dest_realm (string)
   3.15. cxdx_forced_peer (string)
   3.16. append_branches (integer)
   3.17. method_filtering (integer)
   3.18. user_data_always (integer)
   3.19. error_reply_code (int)
   3.20. skip_multiple_bindings_on_reg_resp (int)

3.1. default_expires (int)

   If the processed message contains neither Expires HFs nor expires
   contact parameters, this value will be used for newly created S-CSCF
   usrloc records. The parameter contains number of second to expire (for
   example use 3600 for one hour). If it is set to a lower value than the
   min_expires parameter then it will be ignored. This parameter can be
   modified via ser config framework. A random value in a specific
   interval can be selected by using the default_expires_range parameter

   Default value is 3600.

   Example 1.1. Set default_expires parameter
...
        modparam("ims_registrar_scscf", "default_expires", 3600)
...

3.2. default_expires_range (int)

   This parameter specifies that the expiry used for newly created S-CSCF
   usrloc records are not fixed(when default_expires applies), but a
   random value in the intervalrdq
   [default_expires-default_expires_range%,
   default_expires+default_expires_range%]. The value is between 0 and 100
   and represent the maximum percentage from default_expires that will be
   subtracted or added when computing the value. Default in 0, meaning
   default_expires is left unmodified. This parameter can be modified via
   ser config framework.

   Default value is 0.

   Example 1.2. Set default_expires_range parameter
...
        modparam("ims_registrar_scscf", "default_expires_range", 30) # +- 30% fr
om default_expires
...

3.3. min_expires (int)

   The minimum expires value of a Contact, values lower than this minimum
   will be automatically set to the minimum. Value 0 disables the
   checking. This parameter can be modified via ser config framework.

   Default value is 60.

   Example 1.3. Set min_expiresparameter
...
        modparam("ims_registrar_scscf", "min_expires", 1800)
...

3.4. max_expires (int)

   The maximum expires value of a Contact, values higher than this maximum
   will be automatically set to the maximum. Value 0 disables the
   checking. This parameter can be modified via ser config framework.

   Default value is 0.

   Example 1.4. Set max_expiresparameter
...
        modparam("ims_registrar_scscf", "max_expires", 3600)
...

3.5. subscription_default_expires (int)

   If the processed message contains neither Expires HFs nor expires
   contact parameters, this value will be used for newly created
   subscriptions. The parameter contains number of second to expire (for
   example use 3600 for one hour). If it is set to a lower value than the
   subscription_min_expires parameter then it will be ignored. A random
   value in a specific interval can be selected by using the
   subscription_expires_range parameter

   Default value is 3600.

   Example 1.5. Set subscription_default_expires parameter
...
        modparam("ims_registrar_scscf", "subscription_default_expires", 3600)
...

3.6. subscription_expires_range (int)

   This parameter specifies that the expiry used for newly created
   subscriptions are not fixed(when subscription_default_expires applies),
   but a random value in the interval
   [subscription_default_expires-subscription_expires_range%,
   subscription_default_expires+subscription_expires_range%]. The value is
   between 0 and 100 and represent the maximum percentage from
   subscription_default_expires that will be subtracted or added when
   computing the value. Default in 0, meaning subscription_default_expires
   is left unmodified.

   Default value is 0.

   Example 1.6. Set subscription_expires_range parameter
...
        modparam("ims_registrar_scscf", "subscription_expires_range", 30) # +- 3
0% from subscription_expires_range
...

3.7. subscription_min_expires (int)

   The minimum expires value of a subscription, values lower than this
   minimum will be automatically set to the minimum. Value 0 disables the
   checking.

   Default value is 10.

   Example 1.7. Set subscription_min_expiresparameter
...
        modparam("subscription_min_expires", "min_expires", 1800)
...

3.8. subscription_max_expires (int)

   The maximum expires value of a subscription, values higher than this
   maximum will be automatically set to the maximum. Value 0 disables the
   checking.

   Default value is 1000000.

   Example 1.8. Set subscription_max_expiresparameter
...
        modparam("ims_registrar_scscf", "subscription_max_expires", 3600)
...

3.9. user_data_dtd (string)

   DTD to check the user data received in SAA (Server Assignment Answer).

   Default value is NULL (none).

   Example 1.9. Set user_data_dtdparameter
...
        modparam("ims_registrar_scscf", "user_data_dtd", "/usr/local/etc/kamaili
o/CxDataType_Rel7.dtd")
...

3.10. user_data_xsd (string)

   XSD to check the user data received in SAA (Server Assignment Answer).

   Default value is NULL (none).

   Example 1.10. Set user_data_xsdparameter
...
        modparam("ims_registrar_scscf", "user_data_xsd", "/usr/local/etc/kamaili
o/CxDataType_Rel7.xsd")
...

3.11. support_wildcardPSI (int)

   indicate support for wildcard PSI is subscription profile (SAA)

   Default value is 0.

   Example 1.11. Set support_wildcardPSIparameter
...
        modparam("ims_registrar_scscf", "support_wildcardPSI", 1)
...

3.12. scscf_name (string)

   The name of the S-CSCF

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

   Example 1.12. Set scscf_nameparameter
...
        modparam("ims_registrar_scscf", "scscf_name", "sip:scscf2.ims.smilecoms.
com:6060")
...

3.13. store_profile_dereg (int)

   Should the subscription profile be stored on de-registration

   Default value 0.

   Example 1.13. Set store_profile_deregparameter
...
        modparam("ims_registrar_scscf", "store_profile_dereg", 1)
...

3.14. cxdx_dest_realm (string)

   Destination realm to be used in Diameter messages

   Default value "ims.smilecoms.com"

   Example 1.14. Set cxdx_dest_realmparameter
...
        modparam("ims_registrar_scscf", "cxdx_dest_realm", "my.domain,org")
...

3.15. cxdx_forced_peer (string)

   FQDN of Diameter Peer (HSS) to use for communication (SAR). 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 NULL (none)

   Example 1.15. Set cxdx_forced_peerparameter
...
        modparam("ims_registrar_scscf", "cxdx_forced_peer", "hss.ims.smilecoms.c
om")
...

3.16. append_branches (integer)

   The parameter controls how lookup function processes multiple contacts.
   If there are multiple contacts for the given username in usrloc and
   this parameter is set to 1, Request-URI will be overwritten with the
   highest-q rated contact and the rest will be appended to sip_msg
   structure and can be later used by tm for forking. If the parameter is
   set to 0, only Request-URI will be overwritten with the highest-q rated
   contact and the rest will be left unprocessed. This parameter can be
   modified via Kamailio config framework.

   Default value is 0 (disabled)

   Example 1.16. Set cxdx_forced_peerparameter
...
        modparam("ims_registrar_scscf", "append_branches", 1)
...

3.17. method_filtering (integer)

   Tells if the contact filtering based on supported methods should be
   performed during lookup. It's enabled only if it has a non zero value.

   Default value is 0 (disabled)

   Example 1.17. Set cxdx_forced_peerparameter
...
        modparam("ims_registrar_scscf", "method_filtering", 1)
...

3.18. user_data_always (integer)

   If specified this will make the S-CSCF always request user data from
   HSS.

   Default value is 0 (disabled)

   Example 1.18. Set user_data_alwaysparameter
...
        modparam("ims_registrar_scscf", "user_data_always", 1)
...

3.19. error_reply_code (int)

   In certain error conditions, the S-CSCF may not be able to process the
   request (e.g. in case of database failures). Per default and according
   to the Specs, the S-CSCF would return a 500 error in this case.
   However, according to the SIP-Specs for DNS-SRV, this won't trigger a
   failover, which may be desired.

   This parameter let's you override the default 500 with another
   return-code (e.g. 503) in order to get the desired behaviour.

   Default value is 500.

   Example 1.19. Set error_reply_code parameter
...
        modparam("ims_registrar_scscf", "error_reply_code", 503)
...

3.20. skip_multiple_bindings_on_reg_resp (int)

   If set to 1 - on Re-Registration registrar sends in 200 OK reply only
   current contact in case of multiple bindings. If set to 0 - on
   Re-Registration registrar sends in 200 OK reply all contacts in case of
   multiple bindings according to RFC3261.

   Default value is 0.

   Example 1.20. Set skip_multiple_bindings_on_reg_resp parameter
...
        modparam("ims_registrar_scscf", "skip_multiple_bindings_on_reg_resp", 1)
...

4. Functions

   4.1. save(async_reply_route, domain, mode, flags)
   4.2. lookup(domain)
   4.3. lookup_path_to_contact(uri)
   4.4. unregister(domain)
   4.5. assign_server_unreg(aysnc_reply_route, domain, direction)
   4.6. impu_registered(domain)
   4.7. term_impu_registered(domain)
   4.8. reg_fetch_contacts(domain, uri, profile)
   4.9. reg_free_contacts(profile)
   4.10. can_subscribe_to_reg(domain)
   4.11. subscribe_to_reg(domain)
   4.12. can_publish_reg(domain)
   4.13. publish_reg(domain)

4.1. save(async_reply_route, domain, mode, flags)

   The function processes a REGISTER message. It can add, remove or modify
   usrloc records depending on Contact and Expires HFs in the REGISTER
   message. On success and when called from the REQUEST_ROUTE, 200 OK will
   be returned listing all contacts that are currently in usrloc. On an
   error, error message will be sent with a short description in reason
   phrase. In case of internal errors the function will return FALSE,
   otherwise a force to exit the cfg is file is actioned by returning 0
   (asynchronous processing)

   Meaning of the parameters is as follows:
     * async_reply_route- the route to execute after the save has
       completed. This is required because the save function is executed
       asynchronously (Diameter).
     * domain- Logical domain within registrar.
     * mode- Optional and unused legacy parameter.
     * flags- Optional parameter. Valid values: 0x01 - Realm is not used
       when extracting Private Identity from the Authorization header.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE

   Example 1.21. save usage
...
if (!impu_registered("location")) {
   save("PRE_REG_SAR_REPLY","location");
}
...

4.2. lookup(domain)

   This function extract the IMPU from the Request-URI and tries to find
   all registered contacts in usrloc. If there are no such contacts, -1 is
   returned. If there are, Request-URI will be rewritten with the contact
   that has the highest q value. The rest of the contacts will be appended
   to the sip msg structure (if append_branches is set) and can be later
   used by TM module for forking for example...

   If the method filtering option is enabled, the lookup function will
   only return contacts that support the method of the request being
   processed (see allows header)

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar.

   Return codes:
     * -1 - Not found
     * -2 - Found, but method not allowed (check Allows header for INVITE,
       MESSAGE, etc).
     * -3 - Error occurred internally during processing

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.22. lookup usage
...
lookup("location");
switch ($retcode) {
    case -1:
    case -3:
        sl_send_reply("404", "Not Found");
        exit;
    case -2:
        sl_send_reply("405", "Not Found");
        exit;
};
...

4.3. lookup_path_to_contact(uri)

   This function take a URI and tries to find the contact in usrloc. If
   the contact is found and has a path set, then a path header is added to
   the SIP message so it can be loose routed.

   Meaning of the parameters is as follows:
     * uri - URI of contact to lookup

   Return codes:
     * 1 - Success
     * -1 - Failure

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.23. lookup usage
...
lookup_path_to_contact($ruri);
...

4.4. unregister(domain)

   This function will remove all bindings for the IMPU found in the
   Request-URI.

   Meaning of the parameters is as follows:
     * Domain- Logical domain within registrar.

   This function can be used in REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.24. unregister usage
...
unregister("location");
...

4.5. assign_server_unreg(aysnc_reply_route, domain, direction)

   TBD

   used in REQUEST_ROUTE

4.6. impu_registered(domain)

   This function checks if the IMPU in the To header is registered in
   usrloc.

   Meaning of the parameters is as follows:
     * domain- Logical domain within registrar.

   Return codes:
     * 1 - True, IMPU exists in registered state in usrloc
     * -1 - False, IMPU not registered

   This function can be used in REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.25. impu_registered usage
...
impu_registered("location");
switch ($retcode) {
    case -1:
        sl_send_reply("404", "Not Found");
        exit;
    case 1:
        #true, continue with normal processing
};
...

4.7. term_impu_registered(domain)

   This function checks if the IMPU in the Request-URI is registered in
   usrloc.

   Meaning of the parameters is as follows:
     * domain- Logical domain within registrar.

   Return codes:
     * 1 - True, IMPU exists in registered state in usrloc
     * -1 - False, IMPU not registered

   This function can be used in REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.26. term_impu_registered usage
...
term_impu_registered("location");
switch ($retcode) {
     case -1:
          sl_send_reply("404", "Not Found");
          exit;
     case 1:
          #true, continue with normal processing
};
...

4.8. reg_fetch_contacts(domain, uri, profile)

   The function fetches the contacts for 'uri' from table 'domain' to
   pseudo-variable $imssulc(profile) [imssulc = ims scscf ulc].

   Meaning of the parameters is as follows:
     * domain - Name of table that should be used for the lookup of
       contact addresses.
     * uri - The SIP URI address of the user which to fetch the contact
       addresses for. It can contain pseudo-variables that are evaluated
       at runtime.
     * profile - Name of $imssulc pseudo-variable profile that will store
       the fetched contacts. It is a static string.

   This function can be used in REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.27. reg_fetch_contacts usage
...
reg_fetch_contacts("location", "$ru", "callee");
reg_fetch_contacts("location", "sip:user@kamailio.org", "caller");
...

4.9. reg_free_contacts(profile)

   The function frees the contacts from pseudo-variable $ulc(profile).
   Should be called to release the content of a profile. Anyhow, fetching
   a new contact addresses set over a profile will release any existing
   data in that profile.

   Meaning of the parameters is as follows:
     * profile - Name of $imssulc pseudo-variable profile that stores the
       contacts. It is a static string.

   This function can be used in REQUEST_ROUTE, FAILURE_ROUTE

   Example 1.28. reg_free_contacts usage
...
reg_free_contacts("callee");
...

4.10. can_subscribe_to_reg(domain)

   This function checks to see that a SUBSCRIBE request is authorised to
   subscribe to the particular identity. Only 3 entities can subscribe:
     * The user agent to its own state
     * The P-CSCF specified in the path header for that user
     * Application Server (AS) not yet implemented

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar.

   This function can be used in REQUEST_ROUTE

   Example 1.29. can_subscribe_to_reg usage
...
if (can_subscribe_to_reg("location")){
     $var(ret)= subscribe_to_reg("location");
}
...

4.11. subscribe_to_reg(domain)

   Save the subscription to the REG event for the UAC or the appropriate
   P-CSCF (in the path to the UAC).

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar.

   This function can be used in REQUEST_ROUTE

   Example 1.30. subscribe_to_reg usage
...
if (can_subscribe_to_reg("location")){
     $var(ret)= subscribe_to_reg("location");
}
...

4.12. can_publish_reg(domain)

   This function checks to see that a PUBLISH request is authorised to
   publish for a particular identity. Only 3 entities can publish:
     * The user agent to its own state
     * The P-CSCF specified in the path header for that user
     * Application Server (AS) not yet implemented

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar.

   This function can be used in REQUEST_ROUTE

   Example 1.31. can_publish_reg usage
...
if (can_publish_reg("location")){
    $var(ret)= publish_reg("location");
}
...

4.13. publish_reg(domain)

   Save the publish to the REG event for the UAC or the appropriate P-CSCF
   (in the path to the UAC).

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar.

   This function can be used in REQUEST_ROUTE

   Example 1.32. publish_reg usage
...
if (can_publish_reg("location")){
    $var(ret)= publish_reg("location");
}
...

5. RPC Commands

   5.1. regscscf.dereg_impu

   exported RPC commands.

5.1. regscscf.dereg_impu

   Initiate network de-register of IMPU

6. Statistics

   6.1. registered contacts
   6.2. impus
   6.3. expired contacts

   Exported statistics are listed in the next sections.

6.1. registered contacts

   Number of AOR contacts in registered state - cannot be reset.

6.2. impus

   Number of IMPUs - cannot be reset.

6.3. expired contacts

   Number of expired contacts - can be reset.

Chapter 2. Frequently Asked Questions

   2.1. Where can I find more about Kamailio?
   2.2. Where can I post a question about this module?
   2.3. How can I report a bug?

   2.1.

   Where can I find more about Kamailio?

   Take a look at https://www.kamailio.org/.

   2.2.

   Where can I post a question about this module?

   First at all check if your question was already answered on one of our
   mailing lists:
     * User Mailing List -
       https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
     * Developer Mailing List -
       https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-dev

   E-mails regarding any stable Kamailio release should be sent to
   <sr-users@lists.kamailio.org> and e-mails regarding development
   versions should be sent to <sr-dev@lists.kamailio.org>.

   2.3.

   How can I report a bug?

   Please follow the guidelines provided at:
   https://github.com/kamailio/kamailio/issues.
