[VoiceOps] Dynamic T1 Faxing over IP

Peter R. peter at 4isps.com
Wed Dec 15 19:33:01 EST 2010

The whole connection has to be SIP with hardly any conversion.
So if it G.711 from the customer premise it has to stay G.711 all the 
way to the other fax machine.
It has to be end-to-end. It breaks down when there is a lot of A/D 

On 12/15/2010 5:53 PM, Jeff Anderson wrote:
> We are experiencing a fair amount of heart burn attempting to support 
> faxing over our Dynamic T1 product. Some customers it works great and 
> others have frequent problems.
> We currently support dynamic T1's using both Adtran TA900 series and 
> Cisco IAD2400 services routers. The customers fax machines will 
> connect to their PBX that has a PRI to an IAD/TA. We have the IAD/TA 
> configured for SIP signaling to an Acme SBC selecting T.38 as the 
> preferred codec with fallback to g.711 pass-through. We can force a 
> slower speed, disable error correction, disabled VAD but in the end 
> still have very inconsistent results. From a network perspective the 
> QoS is matching and queuing correctly, the circuits are clean and the 
> IP SLA gives us no reason to believe they are having any network drops 
> or jitter.
> I was wondering if others who have experience with faxing over IP 
> could share what they have learned works best or anything else that 
> may be helpful.
> Any help is greatly appreciated.
> Thanks,
> Jeff
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