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Tricks to improve fax transmissions over IP

New VoIP deployment. 100+ phones, VG-224 with roughly 12-14 fax machines. Call Manager 7. VG-224 is at the same location as 2811 Gateway servicing the PRI. All fax calls come in and leave the PRI. T.38 between 2811 and VG-224.

Had some issues with T1 timing that was resolved with Cisco TAC (we missed a timing config on the 2811). Fax transmission has stabilized. However, speeds are still in the tank. A 24 page document took almost 40 minutes in once case. Any thoughts about what we might be missing? Are there any tips or tricks some of you who have been through this might be able to share with us?



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Re: Tricks to improve fax transmissions over IP


1) Check E1/t1s for clock slips (guess this is what TAC did for you)

2) Disable 'fancy' things on fax machines - particularly ECM or high speed functions. ECM means lots of retries (slowdowns) and potential failures, high speeds generally give bad results. ECM can usually be disabled from the fax menu maze.

3) Check for any packet loss on the IP path, and remediate. Use CDR/CMR logging on CCM to see whether you are experiencing any loss, then try to work out where this occurs if it does.

4) Avoid faxes, send email


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