Fax over SIP

[smarbar]

I am looking for some advice on fax over SIP and when T38 is required. A customer has two scenarios, they are are using Nupoint for incoming and outgoing faxes and they also have a couple of Linksys SPA2102 for physical fax machines in a couple of branch offices both going over SIP trunks. I am told that the SIP trunk provider supports T38 and will use this as the preferred method but will fail back to G711 if not supported by the receiving device.

Does anyone have any experience with either and can help shed some light on what the rules are and when T38 is required please?

[brantn]

T.38 is the recommendation on all faxing over SIP. It allows compression which is a lot more reliable than uncompressed when it comes to faxing. Mitel 3300 site to site must be configured for T.38.

[smarbar]

Thanks Brantn, but are T.38 licenses required on the 3300 if the SIP provider and the SIP client support it?

How does it work for Nupoint?

[brantn]

Not sure on nupoint as I have not done much on that platform with SIP as far as on the 3300 if you are using T.38 you would need T.38 licenses, compression licenses, and dsp II module.