[SIPForum-discussion] Failed called dial-up modem and fax

Mon Aug 17 15:40:15 UTC 2015

Hi Rafael, 
FAX over IP is indeed not that mature yet, and to troubleshoot FAX issues some times its a nightmare! A few days back i got a few guidelines to follow while troubleshooting FAX issues, sharing with you( in good faith, if it helps you minimize daily hectic of going through logs, dsp traces, wireshark captures etc..):
Required Background Information Gathering
 Is the suspected defect observed in the production/field or lab? If it is in a lab, is the customer trying to reproduce a field reported issue? Is it reproducible? What are the call flow, signaling, and media type (eg, codec type and rate)? What is the test procedure? How many pages attempted? Describe the failure and end results such as whether the endpoint received any page at all or displayed any error message. Describe any relevant user observations. Identify both originating and terminating fax equipment brand and model. Identify whether fax calling and answering endpoint are Group 3 or Super Group 3.Identify the name and model of other devices involved (such as other T.38/media GW, PBX, IAD, TDM switch, etc) in the fax call. What is the fax speed set at?What is the fax tone treatment? What is the modem tone treatment? Is there an NBS (or SBC) in the call flow? If so, is it doing relay or transcoding? Is it doing back-to-back T.38 transcoding? Do the customers have the latest NBS (or SBC) release or use a release that has known fax fixes that they should be upgraded to? Is the handset offhook while making/receiving fax call? If so, does the fax endpoint cut off the voice path to the handset once the fax starts?
Also worth reading:http://www.voipmechanic.com/faxingissuesandotherdevices.htmhttps://supportforums.cisco.com/document/54151/fax-over-ip-troubleshooting-basics

Regards, Shah Hussain 
An ounce of practice is worth more than tons of preaching. (Mohandas Gandhi)
"In three words I can sum up everything I've learned about life: it goes on." (Robert Frost)

Date: Sat, 15 Aug 2015 18:19:19 -0300
From: rafaeldiego21 at gmail.com
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Failed called dial-up modem and fax

Hello,
I would like to share with you some of my esperiência on the subject addressed.Daily realize voice network migration, tdm to sip and encounter many problems in relation to fax and dial-up modemIn some cases resolve by adjusting the speed of the equipment, but there are cases that can not solve.I have a question on how to perform a more effective troubleshooting, for I perceive that this is a problem of SIP technology, for these attributes.To adjust the codecs, but sometimes it does not.Working with Cisco and HP routers and no matter what type of router the problem is always the same.I wonder if anyone has experience on this subject.What in the sip could impact on the problem seems addressed attributes.I appreciate the opportunity to be posting on this site.
Sds,

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