16 • SIP Architecture
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S N O M
4 S P
R O X Y
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E G I S T R A R
M
A N U A L
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snom technology AG • 17
[
S N O M
4 S P
R O X Y
/ R
E G I S T R A R
M
A N U A L
]
Registrars
User agents register with a registrar. When a request for the user
agent arrives at the registrar, it redirects the request to the location that
was previously stored in the internal database.
The registrar is the part of the location server that can be
controlled with REGISTER requests. So snom 4S Proxy/Location Server
would be a better name for the product.
Media Server
Strictly speaking, the media server is just a special kind of user
agent. Typically it is able to deal with several calls at the same time and
is a located on a PC or workstation.
The media server has the following tasks:
• Implement mailbox function. When a user is absent, the user
agent of the stateful proxy redirects the call to the mailbox, so that
the caller may leave a message. The owner of the mailbox calls the
mailbox directly to listen to messages.
• Implement music on hold. Using a fat client, all kinds of music
tastes can be played with highest possible quality.
• Implement call parking. Calls can be parked on the media server
until a user picks the call for processing. In the meantime, the
caller can enjoy the music on hold, using DTMF keys to select his
favourites.
• Implement conferencing services. Three or more persons dial
into the conference server, which mixes the audio streams for
each participant and also notifies them of participants joining and
leaving the conference. The conference server also checks the
credentials of participants joining the conference. The snom 4s is
an example of this technology.
Gateways
From a SIP perspective, the gateway is also just a user agent.
Instead of playing the audio stream on a speaker, it sends it to the PSTN
2.
Summary of Contents for 4S Media Server
Page 1: ...Administrator s Manual snom 4S SIP Proxy Registrar Version 2 30 ...
Page 14: ...14 VoIP Protocol S N O M 4 S P R O X Y R E G I S T R A R M A N U A L 1 ...
Page 84: ...84 Routing S N O M 4 S P R O X Y R E G I S T R A R M A N U A L 10 ...
Page 98: ...98 Maintenance S N O M 4 S P R O X Y R E G I S T R A R M A N U A L 13 ...