AudioCodes Mediant 500 E-SBC, User Manual

Page: 448 / 920

User's Manual 448 Document #: LTRT-10437
Mediant 500 E-SBC
27.3.2 SBC Users Registration Database
The device manages a dynamic Users Registration database that is updated according to
registration requests that traverse it. Each database entry for a user represents a binding
between an AOR (obtained from the SIP To header) and one or more contact (obtained
from the SIP Contact headers). Database bindings are added upon successful registration
responses.
Database bindings are removed in the following cases:

Successful de-registration responses (REGISTER with Expires header that equals
zero).

Registration failure responses.

Timeout of the Expires header value (in scenarios where the user agent did not send a
refresh registration request).
Note: The device's Users Registration database poses the following restrictions:
•
The same contact cannot belong to more than one AOR.
•
Contacts with identical URIs and different ports and transport types are not
supported (same key is created).
•
Multiple contacts in a single REGISTER is not supported.
•
One database is shared between all User-type IP Groups.
27.3.3 Routing using Users Registration Database
The device uses the Users Registration database when routing calls of registered users.
The device tries to locate a match for the IP-to-IP Routing rule between the incoming
Request-URI and the following, listed in chronological order:
1. Unique Contact: the contact generated by the device and sent in the initial registration
request to the serving proxy.
2. Registered AOR in the Users Registration database: the AOR of the incoming
REGISTER request.
3. Registered Contact in the Users Registration database: the Contact of the incoming
REGISTER request.
If registrations are destined to the database (using the above rules), the device does not
attempt to find a database match, but instead replies with a SIP 200 OK (used for
Survivability). Once a match is found, the request is routed either to the contact received in
the initial registration or (if the device identifies that the user agent is behind a NAT) to the
source IP address of the initial registration.
27.3.4 Registration Refreshes
Registration refreshes are incoming REGISTER requests that are associated with a
registered user in the Users Registration database. These refreshes are routed to the
serving proxy only if the serving proxy Expires time is about to expire; otherwise, the device
responds with a 200 OK without routing the REGISTER. Each such refreshes also refresh
the internal timer set on the device for this specific registration.
The device automatically notifies SIP Proxy / Registrar servers of users that are registered
in the device's Users Registration database whose registration timeout has expired. When
a user's registration timer expires, the device removes the user record from the database
and sends an un-register notification (REGISTER message with the Expires header set to
0) to the Proxy/Registrar. This occurs only if a REGISTER message is sent to an IP Group
destination type (in the IP-to-IP Routing table).