H3C XE 200 IP, Operation Manual

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Operation Manual – Process Server Configuration
H3C XE 200/2000 IP PBX
Chapter 2 H.323 Overview
2-2
They allow PSTN terminals and H.323 terminals to communicate with each other
transparently.
III. H.323 gatekeeper
H.323 gatekeepers are optional to an H.323 network. They function to manage H.323
network by providing endpoints services such as network access control, call routing
control, and address translation.
IV. H.323 signaling
H.323 protocol suite contains the following three types of signaling:
z
RAS signaling. This type of signaling is used between H.323 gateways and H.323
gatekeepers for operations such as gatekeeper discovery, gateway
registration/unregistration, call access permission, and call release. In a voice
network that contains gatekeepers, RAS signaling channels exist between voice
gateways and gatekeepers. They are established prior to other channels and are
independent of the call control channels and the media control channels. RAS
signaling exchange is necessary for both direct and gatekeeper routed call modes.
A RAS channel is an unreliable channel.
z
H.225.0 call control signaling. This type of signaling is used to set up call
connections between H.323 gateways or between H.323 gateways and
gatekeepers. In a voice network that contains no gatekeepers, a call control
signaling channel is established between the calling gateway and the called
gateway. In a voice network that contains gatekeepers, if the call is set up in direct
call mode, the calling gateway obtains the call address of the called gateway
through RAS signaling exchange, and the call control signaling channel is
established between the calling gateway and the called gateway. Whereas if the
call is setup in routed call mode, the call control signaling channel is established
between the gateway and the gatekeeper. A call control signaling channel is
independent of the RAS channel and H.245 media control channel. It is a reliable
channel.
z
H.245 media channel control signaling. This type of signaling is used to establish
multimedia channels (RTP [real time protocol]/RTCP [RTP control protocol]
channels) between calling gateways and called gateways. The procedure to
establish a multimedia channel contains sub-procedures such as master-slave
determination, capability exchange, and opening logical channels. In this
procedure, the calling and called gateways exchange multimedia information such
as the information about the channel ports and the coding/decoding methods of
them.
In a voice network that contains no gatekeepers, the H.245 media channel control
signaling channel is established between the calling gateway and the called gateway.
The calling gateway obtains the H.245 signaling address of the called gateway through
H.225.0 call control signaling. In a voice network that contains gatekeepers, if the call is