The H.323 Connection; Connection Considerations - 3Com 3C10402B Administrator's Manual

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PPENDIX ONNE
The H.323
Connection
Connection
Considerations
X H.323 G
TIONS ATEWAY
POTS Adapters
You can purchase circuit boards that plug into a personal computer and
adapt an analog telephone (POTS) for use with an H.323 connection.
H.323 Gatekeepers
The gatekeeper is an H.323 entity on the network that provides address
translation and controls access to the network for H.323 terminals,
Gateways, and MCUs. The gatekeeper also provides services to the
terminals, Gateways, and MCUs, such as managing bandwidth and
locating Gateways.
H.323 calls between local and remote 3Com Business and Basic
Telephones are transparent to users, except for the IP dial plan. The Call
Processor sets up the local end of the H.323 call as though it were setting
up a call through a line card. However, this connection actually goes to a
network interface card (NIC) in a dedicated Windows 2000 system that is
running the ConneXtions software.
The Call Processor requests an H.323 port in the ConneXtions software
by sending a frame, with a simulated Ethernet address, that contains a
requested IP address. The ConneXtions gateway uses this address to
request a level three connection between the local router and the remote
router associated with another PBX or NBX system.
After an IP connection has been established, the ConneXtions software
begins a series of H.323 exchanges by using TCP packets on the IP
connection.
These H.323 exchanges set up the call and negotiate the type of voice
compression that is used. They also cause the remote NBX (or PBX)
system to begin setting up the remote end of the connection.
As soon as an end-to-end connection has been set up, all three networks
(local LAN, WAN, and remote LAN) are ready to pass voice packets. The
3Com Business and Basic Telephones use their DSP to convert spoken
words into digital voice packets. The voice packets are transferred across
the Ethernet to the local H.323 gateway. The gateway strips off the
Ethernet frames, compresses the voice, and encapsulates it within UDP
packets which are delivered to the router, again via the Ethernet. The UDP
packets are placed on the WAN for IP delivery to a remote H.323