Fax and Modem Parameters

The fax and modem parameters are described in the table below.

Fax and Modem Parameters

Parameter

Description

'Fax Transport Mode'

configure voip > media fax-modem > fax-transport-mode

[FaxTransportMode]

Determines the fax transport mode used by the device.

[0] Disable = transparent mode
[1] T.38 Relay (default)
[2] Bypass
[3] Events Only

Note: The parameter is overridden by the parameter [IsFaxUsed]. If the parameter [IsFaxUsed] is set to 1 (T.38 Relay) or 3 (Fax Fallback), then [FaxTransportMode] is always set to 1 (T.38 relay).

V34-fax-transport-type

[V34FaxTransportType]

Determines the V.34 fax transport method (whether V34 fax falls back to T.30 or pass over Bypass).

[0] = Transparent
[1] = (Default) Relay
[2] = Bypass
[3] = Transparent with Events

Note: To configure [V34FaxTransportType] to [1] (i.e., fax relay), you also need to configure [FaxTransportMode] to [1] (fax relay).

'V.21 Modem Transport Type'

configure voip > media fax-modem > V21-modem-transport-type

[V21ModemTransportType]

Determines the V.21 modem transport type.

[0] Disable = (Default) Transparent.
[2] Enable Bypass
[3] Events Only = Transparent with Events.

Note: You can also configure this feature per specific calls, using IP Profiles ('Vxx Modem Transport Type' parameter). For more information, see Configuring IP Profiles.

'V.22 Modem Transport Type'

configure voip > media fax-modem > V22-modem-transport-type

[V22ModemTransportType]

Determines the V.22 modem transport type.

[0] Disable = Transparent.
[2] Enable Bypass (default)
[3] Events Only = Transparent with Events.

Note: You can also configure this feature per specific calls, using IP Profiles ('Vxx Modem Transport Type' parameter). For more information, see Configuring IP Profiles.

'V.23 Modem Transport Type'

configure voip > media fax-modem > V23-modem-transport-type

[V23ModemTransportType]

Determines the V.23 modem transport type.

[0] Disable = Transparent.
[2] Enable Bypass (default)
[3] Events Only = Transparent with Events.

Note: You can also configure this feature per specific calls, using IP Profiles ('Vxx Modem Transport Type' parameter). For more information, see Configuring IP Profiles.

'V.32 Modem Transport Type'

configure voip > media fax-modem > V32-modem-transport-type

[V32ModemTransportType]

Determines the V.32 modem transport type.

[0] Disable = Transparent.
[2] Enable Bypass (default)
[3] Events Only = Transparent with Events.

Note:

The parameter applies only to V.32 and V.32bis modems.
You can also configure this feature per specific calls, using IP Profiles ('Vxx Modem Transport Type' parameter). For more information, see Configuring IP Profiles.

'V.34 Modem Transport Type'

configure voip > media fax-modem > V34-modem-transport-type

[V34ModemTransportType]

Determines the V.90/V.34 modem transport type.

[0] Disable = Transparent.
[2] Enable Bypass (default)
[3] Events Only = Transparent with Events.

Note: You can also configure this feature per specific calls, using IP Profiles ('Vxx Modem Transport Type' parameter). For more information, see Configuring IP Profiles.

bell-modem-transport-type

[BellModemTransportType]

Determines the Bell modem transport method.

[0] Disable = (Default) Transparent.
[2] Enable Bypass
[3] Events Only = Transparent with Events.

'Fax CNG Mode'

configure voip > media fax-modem > fax_cng_mode

[FaxCNGMode]

Determines the device's handling of fax relay upon detection of a fax CNG tone or a V.34/Super G3 V8-CM (Call Menu) signal from originating faxes.

[0] Doesn't send T.38 Re-INVITE = (Default) SIP re-INVITE is not sent.
[1] Sends on CNG tone = Sends a SIP re-INVITE with T.38 parameters in SDP to the terminating fax upon detection of a fax CNG tone, if the CNGDetectorMode parameter is set to 1.
[2] Sends on CNG or v8-cn = Sends a SIP re-INVITE with T.38 parameters in SDP to the terminating fax upon detection of a fax CNG tone (if the CNGDetectorMode parameter is set to 1) or upon detection of a V8-CM signal.

Note:

If the parameter is set to [2] and the CNGDetectorMode parameter is set to [0], the device sends a re-INVITE only if it detects a V8-CM signal from the originating fax.
This feature is applicable only if the IsFaxUsed parameter is set to [1] or [3].
The device also sends T.38 re-INVITE if the CNGDetectorMode parameter is set to [2], regardless of the FaxCNGMode parameter settings.

'CNG Detector Mode'

configure voip > media fax-modem > coder

[CNGDetectorMode]

Global parameter that enables the detection of the fax calling tone (CNG) and defines the detection method. You can also configure this feature per specific calls, using IP Profiles ('CNG Detector Mode' parameter). For a detailed description of the parameter and for configuring this feature in the IP Profiles table, see Configuring IP Profiles.

Note: If you configure this feature for a specific IP Profile, the device ignores this global parameter for calls associated with the IP Profile.

'Fax Detect Timeout Since Connect'

fax-detect-timeout-since-connect

[FaxDetectTimeoutSinceConnect]

Defines a timeout (in msec) for detecting fax from the Tel side during an established voice call. The interval starts from when the voice call is established. If the device detects a fax tone within the interval, it ends the voice session and sends a T.38 or VBD re-INVITE message to the IP side and processes the fax. If the interval expires without any received fax event, the device ignores all subsequent fax events during the voice session.

The valid value is 0 to 120000. The default is 0. If set to 0, the device can detect fax during the entire voice call.

Note: The parameter is applicable only to the Gateway application.

'SIP T.38 Version'

configure voip > sip-definition settings > sip-t38-ver

[SIPT38Version]

Defines the T.38 fax relay version.

[-1] Not Configured = (Default) No T.38
[0] Version 0
[3] Version 3 = T.38 Version 3 (V.34 over T.38)

Note:

Interworking of T.38 Version 3 is supported only for Gateway calls. For SBC calls, the device forwards T.38 Version 3 transparently (as is) to the other leg (i.e., no transcoding).
For a description on V.34 over T.38 fax relay, see V.34 Fax Support.

configure voip > media fax-modem > rx-t38-over-rtp-payload-type

[RxT38OverRTPPayloadType]

Defines the received T.38 over RTP payload type.

The valid range is 96 to 127. The default is 106.

Note: The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.

'Fax Relay Enhanced Redundancy Depth'

configure voip > media fax-modem > enhanced-redundancy-depth

[FaxRelayEnhancedRedundancyDepth]

Defines the number of times that control packets are retransmitted when using the T.38 standard.

The valid range is 0 to 4. The default is 2.

'Fax Relay Redundancy Depth'

configure voip > media fax-modem > redundancy-depth

[FaxRelayRedundancyDepth]

Defines the number of times that each fax relay payload is retransmitted to the network.

[0] 0 = (Default) No redundancy
[1] 1 = One-packet redundancy
[2] 2 = Two-packet redundancy

Note: The parameter is applicable only to non-V.21 packets.

'Fax Relay Max Rate' (bps)

configure voip > media fax-modem > max-rate

[FaxRelayMaxRate]

Defines the maximum rate (in bps) at which fax relay messages are transmitted (outgoing calls).

[0] 2400 = 2.4 kbps
[1] 4800 = 4.8 kbps
[2] 7200 = 7.2 kbps
[3] 9600 = 9.6 kbps
[4] 12000 = 12.0 kbps
[5] 14400 = 14.4 kbps (default)
[6] 16800bps = 16.8 kbps
[7] 19200bps = 19.2 kbps
[8] 21600bps = 21.6 kbps
[9] 24000bps = 24 kbps
[10] 26400bps = 26.4 kbps
[11] 28800bps = 28.8 kbps
[12] 31200bps = 31.2 kbps
[13] 33600bps = 33.6 kbps

Note:

The rate is negotiated between both sides (i.e., the device adapts to the capabilities of the remote side). Negotiation of the T.38 maximum supported fax data rate is provided in SIP’s SDP [T38MaxBitRate] parameter. The negotiated [T38MaxBitRate] is the minimum rate supported between the local and remote endpoints.
Fax relay rates greater than 14.4 kbps are applicable only to V.34 / T.38 fax relay. For non-T.38 V.34 supporting devices, configuration greater than 14.4 kbps is truncated to 14.4 kbps.

'Fax Relay ECM Enable'

configure voip > media fax-modem > ecm-mode

[FaxRelayECMEnable]

Enables Error Correction Mode (ECM) mode during fax relay.

[0] Disable
[1] Enable (default)

'Fax/Modem Bypass Coder Type'

[FaxModemBypassCoderType]

Determines the coder used by the device when performing fax/modem bypass. Typically, high-bit-rate coders such as G.711 should be used.

[0] G.711Alaw = (Default) G.711 A-law 64
[1] G.711Mulaw = G.711 Mu-law

configure voip > media fax-modem > fax-modem-telephony-events-mode

[FaxModemNTEMode]

Determines whether the device sends RFC 2833 ANS/ANSam events upon detection of fax and/or modem Answer tones (i.e., CED tone).

[0] = Disabled (default)
[1] = Enabled

Note: The parameter is applicable only when the fax or modem transport type is set to bypass or Transparent-with-Events.

'Fax Bypass Payload Type'

configure voip > media rtp-rtcp > fax-bypass-payload-type

[FaxBypassPayloadType]

Defines the fax bypass RTP dynamic payload type.

The valid range is 0 to 127. The default is 102.

Note: The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.

configure voip > media rtp-rtcp > modem-bypass-payload-type

[ModemBypassPayloadType]

Defines the modem bypass dynamic payload type.

The range is 0 to 127. The default is 103.

Note: The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.

volume

[FaxModemRelayVolume]

Defines the fax gain control.

The range is -18 to -3, corresponding to -18 dBm to -3 dBm in 1-dB steps. The default is -6 dBm fax gain control.

'Fax Bypass Output Gain'

configure voip > media fax-modem > fax-bypass-output-gain

[FaxBypassOutputGain]

Defines the fax bypass output gain control.

The range is -31 to +31 dB, in 1-dB steps. The default is 0 (i.e., no gain).

'Modem Bypass Output Gain'

configure voip > media fax-modem > modem-bypass-output-gain

[ModemBypassOutputGain]

Defines the modem bypass output gain control.

The range is -31 dB to +31 dB, in 1-dB steps. The default is 0 (i.e., no gain).

modem-bypass-output-gain

[FaxModemBypassBasicRTPPacketInterval]

Defines the basic frame size used during fax/modem bypass sessions.

[0] = (Default) Determined internally
[1] = 5 msec (not recommended)
[2] = 10 msec
[3] = 20 msec

Note: When set to 5 msec (1), the maximum number of simultaneous channels supported is 120.

jitter-buffer-minimum-delay

[FaxModemBypasDJBufMinDelay]

Defines the Jitter Buffer delay (in milliseconds) during fax and modem bypass session.

The range is 0 to 150 msec. The default is 40.

enable-fax-modem-inband-network-detection

[EnableFaxModemInbandNetworkDetection]

Enables in-band network detection related to fax/modem.

[0] = (Default) Disable.
[1] = Enable. When the parameter is enabled on Bypass and transparent with events mode (VxxTransportType is set to 2 or 3), a detection of an Answer Tone from the network triggers a switch to bypass mode in addition to the local Fax/Modem tone detections. However, only a high bit-rate coder voice session effectively detects the Answer Tone sent by a remote endpoint. This can be useful when, for example, the payload of voice and bypass is the same, allowing the originator to switch to bypass mode as well.

NSE-mode

[NSEMode]

Global parameter that enables Cisco's compatible fax and modem bypass mode, Named Signaling Event (NSE) packets. You can also configure this feature per specific calls, using IP Profiles ('NSE Mode' parameter). For a detailed description of the parameter and for configuring this feature in the IP Profiles table, see Configuring IP Profiles.

Note: If you configure this feature for a specific IP Profile, the device ignores this global parameter for calls associated with the IP Profile.

NSE-payload-type

[NSEPayloadType]

Defines the NSE payload type for Cisco Bypass compatible mode.

The valid range is 96-127. The default is 105.

Note:

Cisco gateways usually use NSE payload type of 100.
The device ignores this parameter for Rx payload types and uses the payload type determined during SDP negotiation. For using this configured payload type, see the [BackwardPTBehavior] parameter.

'T.38 Max Datagram Size'

configure voip > sip-definition settings > t38-mx-datagram-sz

[T38MaxDatagramSize]

Defines the maximum size of a T.38 datagram that the device can receive. This value is included in the outgoing SDP when T.38 is used.

The valid range is 120 to 600. The default is 560 .

'Detect Fax on Answer Tone'

det-fax-on-ans-tone

[DetFaxOnAnswerTone]

Determines when the device initiates a T.38 session for fax transmission.

[0] Initiate T.38 on Preamble = (Default) The device to which the called fax is connected initiates a T.38 session on receiving . Preamble signal from the fax.
[1] Initiate T.38 on CED = The device to which the called fax is connected initiates a T.38 session on receiving a CED answer tone from the fax. This option can only be used to relay fax signals, as the device sends T.38 Re-INVITE on detection of any fax/modem Answer tone (2100 Hz, amplitude modulated 2100 Hz, or 2100 Hz with phase reversals). The modem signal fails when using T.38 for fax relay.

Note: The parameters is applicable only if the [IsFaxUsed] parameter is set to 1 (T.38 Relay) or 3 (Fax Fallback).

'CED Transfer Mode'

configure voip > media fax-modem > ced-transfer-mode

[CEDTransferMode]

Defines the method for sending fax/modem CED (answering) tones.

[0] Fax Relay or VBD = (Default) The device transfers the CED tone in Relay mode and starts the fax session immediately.
[1] Voice Mode or VBD = The device transfers the CED tone in either Voice or Bypass mode and starts the fax session on V21 preamble.
[2] RFC 4733 Blocking RTP VBD = The device transfers the CED tone in RFC 2833.
[3] RFC 4733 Along with RTP VBD = The device transfers the CED tone in RFC 2833 and bypass, in parallel.

configure voip > sip-definition settings > backward-pt-behavior

[BackwardPTBehavior]

Enables backward compatibility for the following parameters that configure Rx payload types for media features (e.g., RFC 2833 DTMF, RTP redundancy, and fax bypass): [FaxBypassPayloadType], [ModemBypassPayloadType], [RxT38OverRTPPayloadType], [V1501SSEPayloadTypeRx], [V1501SPRTPayloadTypeRx], [NSEPayloadType], [RFC2833RxPayloadType], and [RFC2198PayloadType].

[0] = (Default) Disables backward compatibility. The device only supports media features that are negotiated in SDP (and ignores the configured payload types).
[1] = Enables backward compatibility. The device supports media features by using the configured payload types.