78 System description
The IP trunk card configures two route table entries for the local subnet if a
different ToSis configured for the voice and control packets. Otherwise, a
single entry is created.
CAUTION
Service Interruption
Only technical personnel with detailed knowledge of router
capabilities should make changes to ToS.Improper changes to
ToScan degrade network performance.
Fax support The IP trunk card transfers T.30 protocol (G3 Fax)implementations over
the IP network. Near real-time operational mode is supported where two
T.30facsimile terminals are able to engage in a document transmission in
which the T.30protocol is preser ved.
The trunk uses the T.38 protocol on the connection between a pair of IP
Trunk3.01 (and later) nodes.
The call acts in the same way as a gateway-to-gatewayH.323 call. The call
is set up using the normal voice call process (that is, the normal voice call
codec negotiation process occurs and the correspondingcodec payload size
and jitter buffer valuesare used). When the call setup is complete, the two
G3 Fax terminals are linked. The DSP detects the fax call setup tones and
switches to handle the faxcall. For the remainder of the call, the parameters
administered for the fax call are used (forexample, payload size).
Some implications of the fax call setup process are as follows:
•a voice codec must be configured, evenif only fax calls will be made
•both ends of the call must be able to negotiate to a common voice codec
for the calls to be successful
All T.30session establishment and capabilities negotiation are carried out
between the telephones through the IP trunk cards over the IP Trunk3.01
(and later) network using the T.38protocol. In terms of the inter net fax
service roles, the IP trunk card acts as both the fax on-ramp gateway and
the fax off-ramp gateway,depending on the call direction.
The on-ramp gatewaydemodulates the T.30transmission received from the
originating G3 Fax terminal. The T.30 facsimile control and image data is
transferred in an octet stream structure, using a Real Time Protocol (RTP)
payload, over User Datagram Protocol (UDP) transport mechanism.
Signaling specified by H.323 V.2protocol is used for IP Trunk 3.01 (and
later) to IP Trunk 3.01 (and later) call setup.
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
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