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New Member

Fax over IP problem

I got a 1750 router with one voice port connecting a fax machine, the other site with same config.

Recently I found the content of incoming fax is distorted: the height is only half of the orignal content, and the incoming fax at the other site is OK.

My fax machine is OK and the configs at both routers are just same and this fax over ip has been working for some time. Has some of you come across this problem before?


New Member

Re: Fax over IP problem

I have done several dozens of FAX test between fax machines connected to analog ports on IP enabled devices using G.711ulaw and no fax relay or T.38.

I have a Storm unit from Shunra that I use to cause delay, loss, congestion, bandwidth shaping, etc.

I used 8 paged of medium complexity pages as my base for all tests.

My tests have indicated that low packet loss has a profound impact (as it should). Low levels of packet loss (.5%) were found to cause problems.

Delay caused transfer time problems. A network delay of 10 ms increased the transfer time from 4:20 to 6:10. A 20ms delay increased the transfer time from 4:20 to 7:35.

Jitter caused both quality and transfer time problems. A jitter of 20 ms caused a 30% quality degradation and increased the transfer time from 3:26 to 4:33.


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