SIP Incoming/Outgoing Fax Not Working

[Mustain]

Hi Good People,

Please help me to solve my problem. I have a CUBE that works fine for Voice traffic, and now I'm configuring the T38 protocol to enable the fax service. The problem is FAX can only send/receive faxes if the others are running on SIP too. But if a different side is running on E1, the fax will not work.

I've gathered the debug output from CUBE, but still don't understand what's going on.

The call flow is: ITSP <--> SIP <--> CUBE <--> CUCM <--> MGCP <--> VG224 <--> FAX Machines.

Thanks in advance.

[BalajiSivaraj49175]

SIP message may instruct that following threshold in the configuration

[Mustain]

Hi @BalajiSivaraj49175 

Thank you for your comment, would you like to provide an appropriate reference for your comment?

[BalajiSivaraj49175]

rules for message communication and sampling for channel information.

T.38 - Delay<1000ms, Jitter<300ms, Packet loss should be NONE unless T.38 with redundancy.
Passthrough - Delay<1000ms, Jitter<30ms, Packet loss should be NONE.
Protocol Based switchover - This is standard based.
NSE Based switchover - This is proprietary and works only between Cisco voice gateways.

[BalajiSivaraj49175]

Message communication between differant devices.

[BalajiSivaraj49175]

Can find the referance SIP communication message between the devices(FAX)

https://www.cisco.com/c/en/us/support/docs/voice/session-initiation-protocol-sip/118647-technote-sip-00.html

[BalajiSivaraj49175]

Debug message useful referaance to capture SIP message troubleshoot issue

[BalajiSivaraj49175]

This are different messages communicate between the devises.

[BalajiSivaraj49175]

GW and CUCM message communication frequency message communication when debug this info

[Mustain]

I've tried this, but it still doesn't solve my problem

[Mustain · Accepted solution]

The problem was solved. I tried to uncheck the MTP option on the CUCM SIP Trunk. And some things have been adjusted on the ITSP side such as Codecs, etc.