AEQ
PHOENIX MERCURY
48
One of the objectives of SIP was to contribute a set of processing functions to apply to calls and
capacities present in the public switched telephone network. Thus, it implemented typical
functions that a common telephone terminal offers, such as: calling a number, making a
telephone ring when called, hearing a dial tone or busy tone. The implementation and
terminology in SIP are different.
SIP requires proxy servers and register elements to give a practical service. Although two SIP
terminals can communicate with each other without the mediation of SIP infrastructures through
the use of URIs of the name@IP-address type (which is why SIP is defined as a point-to-point
protocol), this approach is impracticable for a public service because of the problems inherent in
IP addressing, where obtaining static public addresses is nearly impossible and extremely
costly.
To simplify the operation of the unit, AEQ offers, at no additional cost, the services of its
2 own SIP servers (one of them working as main server and the other one as backup
server),
although it cannot guarantee its operation 100% of the time, nor be held responsible for
the inconveniences that this may produce for the end user. The unit leaves the factory
preconfigured with the parameters required to work with the resources of any of these 2 SIP
servers.
SIP makes use of elements called
proxy servers
to help route the requests toward the user’s
current location, authenticate users to give them service, enable call routing policies to be
implemented, and contribute added capabilities to the user.
SIP also contributes register functions that enable the user to inform the proxy servers of his or
her location.
For complete information on the SIP protocol, we recommend consulting:
http://tools.ietf.org/html/rfc3261
C4.1. Working modes.
With the PROXY SIP option activated in the PHOENIX MERCURY, when the unit is started up it
will automatically connect and register itself in the SIP Proxy server configured in its memory,
indicating its name (URI: name@domain) and position (IP address, ports…).
To establish any communication, the unit that wishes to establish the connection will search the
SIP Proxy server register for the information regarding the called device and will redirect the
call—in a way that is transparent to the user—toward the real physical place where the device is
located.
Esquema de funcionamiento protocolo SIP. Fase 1: Registro. Fase 2: Búsqueda del equipo
llamado en la base de datos del servidor SIP. Fase 3: Establecimiento de la conexión
