Background: I spent a month getting this to work and now know more about fax protocols than I ever wanted to. Hope this saves you some time. AT&T installed an IP Flex circuit in June 2011 and we had no problem faxing. From my research, the Cisco Session Border Controller uses a proprietary protocol (not T.37 or T.38) to pass faxes over IP and it works well.
AT&T installed an IP Office 500 in January 2014. We have twelve buildings on a ¾ square mile campus and have gigabit fiber between buildings. The previous phone system used copper and had constant lightning problems. I opted for Patton M/ATA’s to avoid that. They didn’t work as configured. They were set up with G.711 ULAW 64K. The problem is every fax made in the last twenty years uses V.34 at 33.6K. Theoretically you need at least twice the sampling rate (33.6K x 2 = 67.2K > 64K), but in the real world you need three to five times to accurately digitize the sound waves.
Step 1. Go to each fax and reduce the baud rate to 14400 and if that doesn’t work 9600. Most newer Multifunction Printers (MFP) don’t have a baud rate setting, but V.34 needs the Error Correction Mode (ECM) turned on or they step down to 14400. Turn off ECM.
Step 2. In Avaya IP Office Manager, go to Extension and select the extension with the Patton M/ATA you want to configure. Go to the VoIP tab and set Fax Transport Support to T38 (not T38 Fallback); set DTMF Support to RFC2833. Uncheck VoIP Silence Suppression if checked. Go to the T38 Fax tab and uncheck Use Default Values, but don’t change anything. I don’t know why this makes a difference, but it didn’t work with it checked.
Step 3. Login to the Patton ATA’s web page. Go to Telephony, SIP and set the RTP Telephone Event Configuration, Send DTMF Events to Out-of-Band (RFC2833), the Payload will automatically change to 96; Save SIP Settings. Go to Telephone, CODEC and uncheck all of the codecs except the two G711, Silence Suppression Off, and G711U Preferred-codec. Set Jitter Buffer to Fixed Jitter Buffer 40ms. Uncheck FAX without T.38 (Use G.711 fax); Save Codec Configuration. Go to System, Reload and Reset and execute Main Application for change to take effect.
AT&T installed an IP Office 500 in January 2014. We have twelve buildings on a ¾ square mile campus and have gigabit fiber between buildings. The previous phone system used copper and had constant lightning problems. I opted for Patton M/ATA’s to avoid that. They didn’t work as configured. They were set up with G.711 ULAW 64K. The problem is every fax made in the last twenty years uses V.34 at 33.6K. Theoretically you need at least twice the sampling rate (33.6K x 2 = 67.2K > 64K), but in the real world you need three to five times to accurately digitize the sound waves.
Step 1. Go to each fax and reduce the baud rate to 14400 and if that doesn’t work 9600. Most newer Multifunction Printers (MFP) don’t have a baud rate setting, but V.34 needs the Error Correction Mode (ECM) turned on or they step down to 14400. Turn off ECM.
Step 2. In Avaya IP Office Manager, go to Extension and select the extension with the Patton M/ATA you want to configure. Go to the VoIP tab and set Fax Transport Support to T38 (not T38 Fallback); set DTMF Support to RFC2833. Uncheck VoIP Silence Suppression if checked. Go to the T38 Fax tab and uncheck Use Default Values, but don’t change anything. I don’t know why this makes a difference, but it didn’t work with it checked.
Step 3. Login to the Patton ATA’s web page. Go to Telephony, SIP and set the RTP Telephone Event Configuration, Send DTMF Events to Out-of-Band (RFC2833), the Payload will automatically change to 96; Save SIP Settings. Go to Telephone, CODEC and uncheck all of the codecs except the two G711, Silence Suppression Off, and G711U Preferred-codec. Set Jitter Buffer to Fixed Jitter Buffer 40ms. Uncheck FAX without T.38 (Use G.711 fax); Save Codec Configuration. Go to System, Reload and Reset and execute Main Application for change to take effect.
