Sending FAX over SIP trunk

Discussion in 'General' started by yesmat, Mar 21, 2009.

  1. yesmat

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    Hi all,

    I think one of the best features of Elastix over other distros is FAXing capabilities.

    I have one question, could we send faxes, reliably, over SIP trunk and NOT over PSTN FXO interfaces?

    thanks
     
  2. dicko

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    Never reliably over sip unless you have set up "end to end" T38, however with a good VOIP provider and adequate bandwidth I get a 99% or better success rate. (no T38)
     
  3. yesmat

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    99% is pretty good. I understand good provider but what bandwidth is required?
     
  4. ramoncio

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    You will need your faxes to use an uncompressed codec, like g711 or slin.
    If you use g729 or gsm faxes will fail.
    You will also need to configure QoS in your router if you haven't done so yet, and don't use your internet connection exclusively for VoIP.
     
  5. dicko

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    As ramoncio, says, QOS is essential, you need 80k (g711 plus overhead) each way per fax call, latency to the VOIP provider should be less than 40ms. you can afford NO dropped packets, and if possible use prioritized vlan's for the VOIP traffic on your LAN.
     
  6. userfromca

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    I chose elastix over other distributions for this same feature. Using 1.3 stable since it came out. I am able to send fax over IP (g.711) using hylafax as well as from real fax machine connected through PAP2. It does require some tweaking and selecting a good provider. (I have found one that works reliably). Incoming faxes on PSTN come in as pdf files and I can delete all the junk faxes from inbox without wasting any paper.

    BTW It also works great as VOIP server but we all know that :) My last uptime was 38 days and rebooted the server just because I can and have had bad habbit from winblows world.
     

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