User's Manual  668  Document #: LTRT-10632 
 
  Mediant 800B Gateway & E-SBC 
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). 
 
29.4.5  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. 
 
29.4.6  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: 
# clear voip register db sbc user John@10.33.2.22 
# clear voip register db sbc user John 
  To delete all registered users belonging to a specific IP Group: 
# clear voip register db sbc ip-group <ID or name> 
 
29.5  Media Handling 
Media behavior includes anything related to the establishment, management and 
termination of media sessions within the SIP protocol. Media sessions are created using 
the SIP offer-answer mechanism. If successful, the result is a bi-directional media (RTP) 
flow (e.g. audio, fax, modem, DTMF). Each offer-answer may create multiple media 
sessions of different types (e.g. audio and fax). In a SIP dialog, multiple offer-answer 
transactions may occur and each may change the media session characteristics (e.g. IP 
address, port, coders, media types, and RTP mode). The media capabilities exchanged in 
an offer-answer transaction include the following: 
  Media types (e.g., audio, secure audio, video, fax, and text) 
  IP addresses and ports of the media flow 
  Media flow mode (send receive, receive only, send only, inactive) 
  Media coders (coders and their characteristics used in each media flow) 
  Other (standard or proprietary) media and session characteristics