2N BRI Lite/Enterprise v1.1 - Manual (Page 17)

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 Location server – receives registration requests from the UA and updates the
terminal database accordingly.
All the server components (Proxy, Redirect, Location) are mostly on one physical
device called Proxy server, which is responsible for keeping a client database and
connection establishing, maintaining and terminating, as well as call routing.
The 2N BRI gateway VoIP-GSM gateway acts as a UA in any case (has the same
functions as a VoIP phone), i.e. receives call set-up requirements and, on the basis of
its inner LCR table, routes calls to GSM networks.
None of the SIP-defined server components are integrated in the 2N BRI gateway
gateway.
SIP Signalling Messages
Below is a list of messages sent via the SIP:
 INVITE – connection set-up request;
 ACK – INVITE confirmation by the final message addressee;
 BYE – connection termination;
 CANCEL – failed connection cancellation;
 REGISTER – UA registration with the SIP Proxy;
 OPTIONS – server capability query.
The answers to the SIP messages are numerically coded as the case is with the http
protocol. Below are the most important ones:
 1XX – information messages (100 – trying, 180 – ringing, 183 -
progress);
 2XX – successful request completion (200 – OK);
 3XX – request forwarding needed (302 – temporarily moved, 305 – use
Proxy);
 4XX – error (403 – forbidden, 486 – busy here);
 5XX – server error (500 – Server Internal Error, 501 – not implemented);
 6XX – global failure (606 – not acceptable).
 Types of 2N ® BRI Enterprise Connection