ITG User’s Guide
Chapter 3 ITG Concepts
The
ITG
enables
the
transmission
of
voice and fax traffic over any IP network by digitizing
voice
and fax signals, encapsulating the information within IP packets, and then sending the
packets across the IP network
3.1
How the ITG Operates
1.
The TIM inside the ITG digitizes analog voice signals at 8 Kbps.
2.
ITG system software handles the:
y
Capture of telephone number presented as DTMF tones.
y
Mapping the telephone number to the IP address of remote ITG.
y
Setting up calls with remote ITGs
utilizing H.323 call control protocol.
y
Digitizing, compressing and
encapsulating
the voice into IP packets and transmission
of the IP packets onto the Ethernet LAN.
3.
A router attached to the LAN forwards the IP packets
across
the
WAN, where they will
be received by another ITG at the remote.
4.
The process is reversed at the remote ITG.
3.2
ATPM
To allow you to easily dial a telephone or fax on the network, the ITG maps a
series
of
dialed
digits to the IP address of the remote ITG whose phone or fax you are calling.
This
mapping
information is contained in a database inside each ITG called the dial plan.
Based on the dial plan the Address Translation
and
Parsing
Manager
(ATPM) inside the ITG
translate telephony numbers to IP addresses of
remote
ITGs. The ATPM collects telephone
number dialed by users, decides whether the dial string is part of the
dial
plan
and,
if
it
is,
maps it a remote ITG. When the call is
set
up
to the destination, a sub-string of the original
dial string will be sent along to the remote ITG.
3.3
Destination
The destination is where a call is terminated. Typically, for inbound calls from
IP
network,
the ITG terminals the call at one of the
telephony ports. The destination for the call is the
telephony port where the
call
terminated.
For
calls initiated from telephony ports, the ITG
forward the call to a remote ITG via IP network, and the remote ITG terminal the call. The
destination of the call is the remote ITG.
3.4
Hunt
Group
Instead
of
directly
mapping
a
phone
number to a destination, the ATPM first maps the phone
number to a group of destinations known
as
a Hunt Group. A hunt group is a group of
destinations that are equivalent.
For example, the customer support group of a company
Configuring ITG from a Web Browser
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