Registration Refreshes; Registration Restriction Control; Deleting Registered Users - AudioCodes E-SBC User Manual

CHAPTER 30 SBC Overview

Registration Refreshes

Registration refreshes are incoming REGISTER requests from users that are registered in the
device's registration database. The device sends these refreshes to the serving proxy only if the
serving proxy's Expires time is about to expire; otherwise, the device responds with a 200 OK to
the user without routing the REGISTER. Each such refresh also refreshes 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 its
registration database and whose registration timeout has expired. When a user's registration timer
expires, the device removes the user's 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).
You can also apply a graceful period to unregistered requests, using the 'User Registration Grace
Time' parameter (SBCUserRegistrationGraceTime):
■ You can configure the device to add extra time (grace period) to the expiration timer of
registered users in the database. If you configure this grace period, the device keeps the user
in the database (and does not send an un-register to the registrar server), allowing the user to
send a "late" re-registration to the device. The device removes the user from the database only
when this additional time expires.
■ The graceful period is also used before removing a user from the registration database when
the device receives a successful unregister response (200 OK) from the registrar/proxy server.
This is useful in scenarios, for example, in which users (SIP user agents) such as IP Phones
erroneously send unregister requests. Instead of immediately removing the user from the
registration database upon receipt of a successful unregister response, the device waits until it
receives a successful unregister response from the registrar server, waits the user-defined
graceful time and if no register refresh request is received from the user agent, removes the
contact (or AOR) from the database.
The device keeps registered users in its' registration database even if connectivity with the proxy is
lost (i.e., proxy does not respond to users' registration refresh requests). The device removes users
from the database only when their registration expiry time is reached (with the additional grace
period, if configured).

Registration Restriction Control

The device provides flexibility in controlling user registrations:
■ Limiting Number of Registrations: You can limit the number of users that can register with
the device per IP Group, SIP Interface, and/or SRD, in the IP Group, SIP Interface and SRDs
tables respectively. By default, no limitation exists.
■ Blocking Incoming Calls from Unregistered Users: You can block incoming calls (INVITE
requests) from unregistered users belonging to User-type IP Groups. By default, calls from
unregistered users are not blocked. This is configured per SIP Interface or SRD. When the call
is rejected, the device sends a SIP 500 (Server Internal Error) response to the remote end.

Deleting Registered Users

You can remove registered users from the device's registration database through CLI:
■ To delete a specific registered user:
# clear voip register db sbc user <AOR of user – user part or user@host>
For example:
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