Simultaneous Negotiation Of Fax (T.38) And Modem (V.150.1) Relay - AudioCodes Mediant 3000 User Manual

Media gateway & enterprise session border controller (e-sbc)

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To configure V.150.1 Modem relay:

In the Coders Table (Configuration tab > VoIP menu > Coders and Profiles >

Coders), set the coder to V.150.

On the Fax/Modem/CID Settings page, configure the V.150.1 parameters appearing

under the 'V.150.1 Modem Relay Settings' group:

Set the 'Profile Number' parameter (V1501AllocationProfile) to the amount of

DSP channels allocated for regular voice and V.150.1 Modem Relay capability.

Once the V.150.1 session has been negotiated and activated by SIP, a Modem

Relay DSP channel is allocated alongside the existing allocated voice DSP

channel. The DSP Modem Relay channel is responsible for the entire V.150.1

part of the call. The table below lists the currently supported DSP allocation

Table 15-1: DSP Allocation Options for V.150.1 Modem Relay

TP-8410 16 E1/21 T1

The TP-8410 16 E1/21 T1 blade provides 6 DSPs, supporting up to 21 DS1

spans. The TP-8410 and TP-6310 blades provide 21 DSPs, supporting up to 84

The Number Of Voice Channels column represents channel density when the

blade supports SRTP.

Set the 'SSE Payload Type Rx' parameter to the V.150.1 SSE payload type that

the device uses when it offers the SDP.

Set the 'SSE Redundancy Depth' parameter to the number of sent SSE

redundant packets. The parameter is important in case of network impairments.

For additional V.150.1 related parameters, see ''Fax and Modem Parameters'' on

15.2.5 Simultaneous Negotiation of Fax (T.38) and Modem (V.150.1)

The device can negotiate fax relay (T.38) and modem relay (V.150.1) sessions in the

same, already established call channel. Fax relay sessions require bypass answering tone

(CED) while modem relay requires RFC 2833 answering tone. As the device is not always

aware at the start of the session whether the answering tone is fax or modem, it uses both

methods for CED tone transfer and sends both answering tone types. Only when the

answering tone is detected, does the device send the fax or modem.

To support this functionality, you need to configure a Coders Group (in the Coders Group

table - see ''Configuring Coder Groups'' on page 385) that includes the T.38, V.150, and

G.711/VBD coders.

Profile Number

Number of Voice

Number of Modem

Mediant 3000