FAXes on SIP g711, need T.38

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Mar 12th, 2009
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We are about to implement a SIP trunk for our voice network.

We also have Xmedius as out FAX server.

Xmedius only supports T.38 fax relay, whereas we are trying to use G711ulaw natively or fax pass through.

Is there a workaround for this so we can use the SIP and Xmedius?

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Overall Rating: 5 (3 ratings)
gogasca Thu, 03/12/2009 - 23:00
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yes use cucm 4.2 or above.

7.0 has new features for exchange t.38 methods.

also if using mtp in sip trunk (early offer required) u will need ios 5.x and up for codec pass-trough support.

let us know what is the exact topology.

Nicholas Matthews Fri, 03/13/2009 - 20:22
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Unfortunately this isn't directly supported.

Since Xmedius is limited to T38, and the SIP trunk is limited to G711, you need to 'transcode' your G711 to T38.

There aren't any IOS gateways that support transcoding different types of fax codecs between call legs.

What you can do is create an analog loopback by connecting two PRI ports back-to-back on a single router via a T1 crossover cable, and terminate each end of the PRI with a different fax protocol.



It's kind of wacky, but it should work.



wilson_1234_2 Sat, 03/14/2009 - 10:31
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Thanks for the excellent reply nic, I will give that a try.


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