1. Registrar Module

Jan Janak

   FhG FOKUS

   Copyright © 2003 FhG FOKUS
   Revision History
   Revision $Revision: 1.11.6.1 $ $Date: 2008/06/11 13:12:02 $
     __________________________________________________________________

   1.1. Overview
   1.2. NAT Support In Registrar
   1.3. Synchronizing UA Internal Clock
   1.4. Processing +sip.instance parameter
   1.5. Dependencies
   1.6. Parameters

        1.6.1. default_expires (integer)
        1.6.2. min_expires (integer)
        1.6.3. max_expires (integer)
        1.6.4. default_q (integer)
        1.6.5. append_branches (integer)
        1.6.6. use_domain (integer)
        1.6.7. case_sensitive (integer)
        1.6.8. desc_time_order (integer)
        1.6.9. received_avp (integer)
        1.6.10. received_param (integer)
        1.6.11. max_contacts (integer)
        1.6.12. retry_after (integer)

   1.7. Functions

        1.7.1. save(domain)
        1.7.2. save_noreply(domain)
        1.7.3. lookup(domain)
        1.7.4. registered(domain)

1.1. Overview

   The module contains REGISTER processing logic.

1.2. NAT Support In Registrar

   Registrar and usrloc modules implement NAT extensions that ensure that
   SIP messages beging sent to registered contacts would use the same
   socket (with the same IP address and port) on which the REGISTER that
   registered the contact had been received. REGISTER messages generated
   by user agents behind NAT ofter open a pinhole in the NAT because
   REGISTER is usually the first message sent from the user agent to the
   SIP server. A small example follows.

   Let's suppose that we have a single SER instance listening on two ports
   -- 5060 and 5090. Using a different port seems to be often necessary
   because of broken SIP ALGs (Application Level Gateways) that are often
   built into DSL routers or other devices. Such ALGs would mangle SIP
   requests and responses coming to and from port 5060 and the only option
   how to avoid such mangling is using a different port number.

   Let's suppose that we have two UAs beind NAT, one of them is configured
   to reach SER on port 5060, the other one is configured to use port 5090
   (due to the reasons described above):
                      SER
                  +---------+
UA1 ---- NAT1 ----| 5060    |
                  |         |
UA2 ---- NAT2 ----| 5090    |
                  +---------+

   Registrar and usrloc would store the public IP of NAT with each
   registered contact, thus it would know how to reach both user agents.

   In addition to the publi IP and port of the NAT device, registrar would
   also remember the destination IP and port of the REGISTER request (the
   IP and port used in SER). If registrar did not store this information,
   it would not know what outbound socket it should use when sending SIP
   messages to the registered contact. It would use the default port
   number (often 5060) for such outgoing requests.

   When an INVITE for UA1 comes, everything would work because UA1 used
   port 5060 when registering and that is also the destination port in the
   pinhole being kept open in NAT1:
                                 SER
                 INVITE UA1  +--------+     INVITE UA1
UA1 ---- NAT1 <------------- |  5060  | <----------------
                             |        |
UA2 ---- NAT2                |  5090  |
                             +--------+

   When an INVITE for UA2 comes, SER would again use port 5060 as the
   default outgoing source port number, but this time the message will be
   dropped by NAT2, because the pinhole opened during the registration has
   5060 as the destination port number:
                                 SER
                 INVITE UA2  +--------+     INVITE UA2
UA1 ---- NAT1        +------ |  5060  | <---------------
                     |       |        |
UA2 ---- NAT2 X <----+       |  5090  |
                             +--------+

   That is the reason why registrar and usrloc also need to remmember the
   IP and port used on the server side, that information would be used
   later when forwarding INVITEs:
                                 SER
                             +--------+     INVITE UA2
UA1 ---- NAT1                |  5060  | <---------------
                 INVITE UA2  |        |
UA2 ---- NAT2 <------------- |  5090  |
                             +--------+

Note

   The X next to NAT2 has disappeared in this picture which means that the
   message will be lucky enough to make it through.

   SER would encode this information into a SIP URI when saving contacts
   in database and later, after restart of SER, this information will be
   restored. The URI looks like:
sip:1.2.3.4:5060;dstip=5.6.7.8;dstport=5090

   Where the hostname part is the public IP of the NAT, the port (5060) is
   the port allocated by the NAT, "dstip" parameter is the IP used on SER
   side and "dstport" parameter is the port number used on SER side during
   registration. This information is later used to find the correct
   outgoing socket in SER. If no such socket can be found (it can happen
   if you reconfigure SER to use different ports or IPs), it will use the
   default IP/port again.

1.3. Synchronizing UA Internal Clock

   Many existing user agents support date and time synchronization from
   the registrar. Registrar can append "Date" header field to the 200 OK
   to REGISTER message received from the user agent. User agents that
   support time synchronization would read the current date and time from
   the header field and set internal clock to it. For example:
SIP/2.0 200 OK
Via: SIP/2.0/UDP 62.240.165.98;branch=z9hG4bK3E66B9EB
CSeq: 1469 REGISTER
To: "1 1" <sip:jan@charon.ok2rab.cz>;tag=2bd21cbe8bf183397d829c66d62463e6.0aea
From: "1 1" <sip:jan@charon.ok2rab.cz>
Call-ID: 1767561454@62.240.165.98
Date: Fri, 02 Sep 2005 11:20:12 GMT

   You can use append_time function from textops module to append the
   header field to the reply. Put the function before save("location"); in
   the configuration file.

   Example 1. Adding Date header to Replies
if (uri == myself) {
    if (method == "REGISTER") {
        append_time();
        save("location");
        break;
    };
};

1.4. Processing +sip.instance parameter

   The GRUU extension for SIP (draft-ietf-sip-gruu-04) adds a new
   parameter to the URI of the Contact header in the REGISTER request to
   identify a UA instance globaly unique in the world. This is reached by
   adding a globaly unqiue identifier, the so called sip instace, as a
   parameter to the Contact URI within all REGISTER requests.

   Example 2. A Contact header with sip instance parameter
Contact: <sip:nils@192.168.0.122:2532>;q=1.0;+sip.instance="<urn:uuid:6a66f3bd-5
b1f-448a-a8be-e29572ea3bee>"

   By looking at this sip instance parameter the registrar can decide if
   the incoming request is just an update of an existing Contact URI or if
   a new Contact URI has to be added to the AOR of this account. Thus even
   after a reboot of the UA the new REGISTER can be determined the request
   as an update of an old, already existing entry.

   The registrar module now looks for the sip instance parameter in the
   Contact URI:
     * If the sip instance parameter is not present in the URI of the
       Contact header the algorithm stays the same as like before the GRUU
       extension. Which means the registrar only compares the SIP URI from
       the Contact header with the existing URIs for the AOR (account). If
       exactly the same URI already exists the existing entry will be
       updated, otherwise the URI will be added to the list.
     * If the sip instace parameter is present in the URI of the Contact
       header it will be first searched for an existing Contact with
       exactly the same sip instance value. If an URI with exactly the
       same sip instance value exists already in the database, the
       existing entry will be replaced with the new value, no matter if
       they differ or not. If no Contact with this sip instance value
       exists a new entry for it will be added.

   For example the following Contact would replace the Contact value from
   the example above in the usrloc database because the sip instance value
   is the same, although the Contact URI differs. Without the sip instance
   this would have created two entries in the usrloc database.

   Example 3.
Contact: <sip:lando@192.168.0.2:2500>;q=1.0;+sip.instance="<urn:uuid:6a66f3bd-5b
1f-448a-a8be-e29572ea3bee>"

1.5. Dependencies

   Registrar module depends on the following SER modules:
     * usrloc - User Location Module.
     * sl - Stateless Replies.

1.6. Parameters

   Revision History
   Revision $Revision: 1.11.6.1 $ $Date: 2008/06/11 13:12:02 $

1.6.1. default_expires (integer)

   If the processed message contains neither Expires HFs nor expires
   contact parameters, this value will be used for newly created usrloc
   records. The parameter contains number of second to expire (for example
   use 3600 for one hour).

   Default value is 3600.

   Example 4. Set default_expires parameter
...
modparam("registrar", "default_expires", 1800)
...

1.6.2. min_expires (integer)

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

   Default value is 60.

   Example 5. Set min_expires parameter
...
modparam("registrar", "min_expires", 60)
...

1.6.3. max_expires (integer)

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

   Default value is 0.

   Example 6. Set max_expires parameter
...
modparam("registrar", "max_expires", 120)
...

1.6.4. default_q (integer)

   The parameter represents default q value for new contacts. Because ser
   doesn't support float parameter types, the value in the parameter is
   divided by 100 and stored as float. For example, if you want default_q
   to be 0.38, use value 38 here.

   Default value is 0.

   Example 7. Set default_q parameter
...
modparam("registrar", "default_q", 100)
...

1.6.5. 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.

   Default value is 1.

   Example 8. Set append_branches parameter
...
modparam("registrar", "append_branches", 0)
...

1.6.6. use_domain (integer)

   If set to 1 then the registrar will use username@domain as address of
   record. If the variable is set to 0 then only username will be used as
   the address of record.

   Default value is 0.

   Example 9. Set use_domain parameter
...
modparam("registrar", "use_domain", 1)
...

1.6.7. case_sensitive (integer)

   If set to 1 then AOR comparison will be case sensitive, if set to 0
   then AOR comparison will be case insensitive--This is recommended.

   Default value is 0.

   Example 10. Set case_sensitive parameter
...
modparam("registrar", "case_sensitive", 1)
...

1.6.8. desc_time_order (integer)

   If set to 1 then all contacts will be ordered in descending
   modification time order. In this case the most recently updated/created
   contact will be used.

   Default value is 0.

   Example 11. Set desc_time_order parameter
...
modparam("registrar", "desc_time_order", 1)
...

1.6.9. received_avp (integer)

   Registrar will store the value of the AVP configured by this parameter
   in the received column in the user location database. It will leave the
   column empty if the AVP is empty. The AVP should contain a SIP URI
   consisting of the source IP, port, and protocol of the REGISTER message
   being processed.

Note

   The value of this parameter should be the same as the value of
   corresponding parameter of nathelper module.

   Default value is 42.

   Example 12. Set received_avp parameter
...
modparam("registrar", "received_avp", 43)
...

1.6.10. received_param (integer)

   The name of the parameter that will be appended to Contacts of 200 OK
   when the received URI was set by nathelper module.

   Default value is "received".

   Example 13. Set received_param parameter
...
modparam("registrar", "received_param", "rcv")
...

1.6.11. max_contacts (integer)

   The parameter can be used to limit the number of contacts per AOR
   (Address of Record) in the user location database. Value 0 disables the
   check.

   Default value is 0.

   Example 14. Set max_contacts parameter
...
# Allow no more than 10 contacts per AOR
modparam("registrar", "max_contacts", 10)
...

1.6.12. retry_after (integer)

   The registrar can generate 5xx reply to REGISTER in various situations.
   It can, for example, happen when the max_contacts parameter is set and
   the processing of REGISTER request would exceed the limit. In this case
   the registrar would generate "503 Service Unavailable" response.

   If you want to add the Retry-After header field in 5xx replies, set
   this parameter to a value grater than zero (0 means do not add the
   header field). See section 20.33 of RFC3261 for more details.

   Default value is 0 (disabled).

   Example 15. Set retry_after parameter
...
modparam("registrar", "retry_after", 30)
...

1.7. Functions

   Revision History
   Revision $Revision: 1.11.6.1 $ $Date: 2008/06/11 13:12:02 $

1.7.1.  save(domain)

   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, 200 OK will be returned listing all contacts that
   are currently in usrloc. On an error, error message will be send with a
   short description in reason phrase.

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar. If database is used then
       this must be name of the table which stores the contacts.

   Example 16. save usage
...
save("location");
...

1.7.2.  save_noreply(domain)

   Same as save() but it doesn't send a reply.

   Meaning of the parameters is as follows:
     * domain - Logical domain within registrar. If database is used then
       this must be na e of the table which stores the contacts.

   Example 17. save_noreply usage
...
save_noreply("location");
...

1.7.3.  lookup(domain)

   The functions extracts username from Request-URI and tries to find all
   contacts for the username in usrloc. If there are no such contacts, -1
   will be returned. If there are such contacts, Request-URI will be
   overwritten with the contact that has the highest q value and
   optionally the rest will be appended to the message (depending on
   append_branches parameter value).

   Meaning of the parameters is as follows:
     * domain - Name of table that should be used for the lookup.

   Example 18. lookup usage
...
lookup("location");
...

1.7.4.  registered(domain)

   The function returns true if the AOR in the Request-URI is registered,
   false otherwise. The function does not modify the message being
   process, it neither rewrites the Request-URI if a contact is found not
   append branches.

   Meaning of the parameters is as follows:
     * domain - Name of table that should be used for the lookup.

   Example 19. registered usage
...
if (registered("location")) {
    sl_send_reply("100", "Trying");
    ...
};
...
