Specifications
TD 92326GB
2009-03-10 / Ver. E
Installation and Operation Manual
VoIP Gateway
135
and accessible if the ID is OK. Devices that log on to the gatekeeper using the RAS
protocol are configured in “Gatekeeper client group mode”.
Figure 123. Call sequence with two gatekeepers and RAS
A number of VoIP devices do not support the RAS protocol. Such devices can nevertheless
still be managed by being statically configured (hence with fixed IP addresses) in the
gatekeeper. Steps 1 and 2 then no longer apply in the sequence in figure 122 on page
133. Such devices are configured in “Gateway” or “Gateway group” mode.
The VoIP Gateway itself can also log on to another gatekeeper with RAS protocol as
illustrated in figure 123. This operating mode is configured in “Registration at Gatekeeper
as endpoint” or “Registration at Gatekeeper as Gateway” mode.
19.1.1 Gatekeeper Discovery
Gatekeeper discovery works via IP multicast packets which a gatekeeper client transmits if
it wants to find a suitable gatekeeper.
Normally such packets are only transmitted within one's own LAN segment and, in
particular, are not routed into other networks. That is why gatekeepers can only be found
within one's own LAN segment. However, routers can be configured so that they transfer
such packets according to certain rules. This makes it possible to also find gatekeepers
which are connected via WAN links.
The difference made is based on the so called multicast addresses. The multicast address
used for gatekeeper discovery is 224.0.1.41.
19.1.2 The Gatekeeper Identifier (ID)
Each gatekeeper within a network can be identified by means of its own Gatekeeper
Identifier (ID), i.e. the name defined in the GUI. This ID allows the administrator to operate
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