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1.5.1
SIP proxy and SIP gateway
The tasks involved in switching calls between the different lines of SIP and
ISDN subscribers are handled by two functions in the LANCOM VoIP Router.
SIP proxy
A SIP proxy handles the switching between callers.
SIP gateway
The SIP gateway handles the conversion between IP-based telephony that
uses the SIP protocol and other (telephone) networks, for example the
ISDN network.
1.5.2
User registration at the SIP proxy
A LANCOM VoIP Router represents the central exchange for SIP calls between
different subscribers who wish to communicate over different types of line.
The task of switching in the LANCOM are handled by the SIP proxy. A tele-
phone signals the SIP proxy that it needs to establish a connection, and the
SIP proxy uses certain rules to decide which line is to be used for the connec-
tion. Conversely, incoming calls are assigned to a certain terminal device by
the SIP proxy according to its rules.
For terminal devices to be able to take part in this switching, they must be reg-
istered with the SIP proxy. Where the registration is limited to call switching
by the LANCOM, we refer to "local registration".
If other exchanges are involved, e.g. an SIP PBX at another location, then we
refer to an upstream registration. In this case, the LANCOM accepts the
request for registration and forwards it upstream. In this instance, the
LANCOM is described as "transparent proxy".
Local registration
User
LANCOM as SIP proxy
LANCOM 1722 VoIP – LANCOM 1724 VoIP
Upstream registration
Internet
VPN
Chapter 1: Introduction
SIP PBX
23
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