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M3SR Series 4100
Figure 5.36 SIP and Proprietary Signalling (ACCEPT, Endpoint Radio)
Figure 5.36: An external VoIP user calls the radio network; a radio accepts the incoming call
(automatic call accept delay timer is interrupted), the call session is successfully established
and, eventually, a radio terminates the call session.
5.5.3.2
SIP Signalling
As a SIP user agent, the VoIP gateway radio supports the exchange of SIP messages with
another SIP user agent over the IP network. Since it can act as a UAC and a UAS, the VoIP
gateway radio can send request or return responses.
VoIP Gateway Radio Invites an External VoIP User to a SIP Session
In Figure 5.36 the transaction of a SIP session establishment, which has been started from
the VoIP gateway radio, is shown.
If the VoIP gateway radio wants to establish a SIP session with an external VoIP user, it acts
as a UAC and sends an "INVITE" request to the target VoIP user. Afterwards, the VoIP gate-
way radio waits for a SIP response "200 OK" with session description. This is not necessarily
the destination VoIP user, it may be another SIP identity in the IP Network, e.g. a proxy serv-
er, which should send the "100 Trying" response as soon as it has received the "INVITE" re-
quest. This is a provisional response intended to avoid that the VoIP gateway radio resends
an "INVITE" before the first has been completely processed at the target VoIP user.
5.122
SIP Proxy
Gateway Radio
both way
RTP media
SIP Signalling
SIP – Useful Information for System Integration
Endpoint Radios
Broadcast
Proprietary Signalling
ICN-4G-N-231054-R-D0894-00009-A-01-1
Operating Manual 6172.5808.02 – 01
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