R&S M3SR 4100 Series, Operating Manual

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M3SR Series 4100 SIP – Useful Information for System Integration
5.122 Operating Manual 6172.5808.02 – 01
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.
100 Trying
CONNECTED
ICN-4G-N-231054-R-D0894-00009-A-01-1
both way
RTP media
Broadcast
200 OK
BYE RELEASED
SIP Proxy Gateway Radio Endpoint Radios
SIP Signalling Proprietary Signalling
INVITE
INCOMING
180 Ringing
200 OK
ACK
HANG UP
ACCEPT