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mgcp config to perform G711 fax correcly even if T38 enabled

AS5850 Cisco IO12.4(7c),

The used protocol is MGCP with a call agent.

the behaviour we want for the gateway is to be able

to have fax transmission in G711 codec

without nse - without t38

The mgcp parameters are on mgcp side

MGCP Admin State ACTIVE, Oper State ACTIVE - Cause Code NONE

MGCP call-agent: 172.20.xx.xx 2727 Initial protocol service is MGCP 1.0

MGCP validate call-agent source-ipaddr DISABLED

MGCP validate domain name DISABLED

MGCP block-newcalls DISABLED

MGCP send SGCP RSIP: forced/restart/graceful/disconnected DISABLED

MGCP quarantine mode process/loop

MGCP quarantine of persistent events is ENABLED

MGCP dtmf-relay voip codec all mode out-of-band

MGCP dtmf-relay for voAAL2 is SDP controlled

MGCP voip modem passthrough disabled

MGCP voaal2 modem passthrough disabled

MGCP voip modem relay: Disabled.

MGCP T.38 Named Signalling Event (NSE) response timer: 200

MGCP Network (IP/AAL2) Continuity Test timer: 200

MGCP 'RTP stream loss' timer disabled

MGCP request timeout 3000

MGCP maximum exponential request timeout 4000

MGCP gateway port: 2427, MGCP maximum waiting delay 5

MGCP restart delay 0, MGCP vad DISABLED


MGCP system resource check DISABLED

MGCP xpc-codec: DISABLED, MGCP persistent hookflash: DISABLED

MGCP persistent offhook: ENABLED, MGCP persistent onhook: DISABLED

MGCP piggyback msg DISABLED, MGCP endpoint offset DISABLED

MGCP simple-sdp ENABLED

MGCP undotted-notation ENABLED

MGCP codec type g729r8, MGCP packetization period 40

MGCP JB threshold lwm 4, MGCP JB threshold hwm 100

MGCP LAT threshold lwm 150, MGCP LAT threshold hwm 300

MGCP PL threshold lwm 1000, MGCP PL threshold hwm 10000

MGCP CL threshold lwm 1000, MGCP CL threshold hwm 10000

MGCP playout mode is adaptive 50, 30, 100 in msec

MGCP Fax Playout Buffer is 300 in msec

MGCP media (RTP) dscp: ef, MGCP signaling dscp: ef

MGCP default package: trunk-package

MGCP supported packages: gm-package dtmf-package trunk-package rtp-package

ms-package dt-package mo-package res-package mt-package


MGCP Digit Map matching order: shortest match

SGCP Digit Map matching order: always left-to-right

MGCP VoAAL2 ignore-lco-codec DISABLED

MGCP T.38 Max Fax Rate is 14400 bps



MGCP T.38 Fax NSF Override is DISABLED

MGCP T.38 Fax Low Speed Redundancy: 0

MGCP T.38 Fax High Speed Redundancy: 0

MGCP control bound to interface Loopback2

MGCP media bound to interface Loopback1

MGCP Upspeed payload type for G711ulaw: 0, G711alaw: 8

MGCP Dynamic payload type for G.726-16K codec

MGCP Dynamic payload type for G.726-24K codec

MGCP Dynamic payload type for G.Clear codec

MGCP Dynamic payload type for NSE is 100

MGCP Dynamic payload type for NTE is 101

MGCP Guaranteed scheduler time is disabled

The T38 is enabled on the gateway but the CA doesn't ask for a T38 fax

The Fax must work in V17 (group3)

The comm is established direclty to G711

The CA send REQNT for ft d?tection

The MGW send NTFY when the ft is observed

but it send also 3 NSE packets PT=100.

Which is very surprising because we are no modem passthrough mode nse.

If we modify the mgcp configuration, there is nore more paquets NSE


our wish is to have only a configuration from which it must be possble to perform g711 ot t38 fax using

mgcp (without modification of the GW depending on the service type that can used it)

is there some additionnal modification on this GW possible to perform this.


Re: mgcp config to perform G711 fax correcly even if T38 enabled

You do not have to enable the CAS MD package with the mgcp package-capability command. The CAS MD package is enabled automatically when a T1 controller is configured for FGD EANA signaling using the ds0-group command.