Hello All,
Do you have someone working IP connection between 4400 (R5Ux) and Cisco. I have no problem with voice over IP. I try to send FAX over IP (T38) protocol. During FAX sending INTIP board goes out. (without incident).
For Enterprise we have some IP and FAX parameters (40 ms framing and so on). But what about 4400? In TC I found only one approved device MP-102.
I just want to know - somewhere FAX over IP (T38) between 4400 (before Linux) and non Alcatel device works or no.
T38 FAX over IP
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IceMan_DUP
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bbocjcp
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cavagnaro
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gundam
Fax on VoIP s*&ks!
I have a customer running pure VoIP environment and using Audiocode equipment for FAX mechines.
During the day, faxing anything was crap shooot, but at night, it works great.
Told the customer this is a bendwidth issue and was told by the customer they have QoS running on the voice traffic.
I hate
VoIP 
I have a customer running pure VoIP environment and using Audiocode equipment for FAX mechines.
During the day, faxing anything was crap shooot, but at night, it works great.
Told the customer this is a bendwidth issue and was told by the customer they have QoS running on the voice traffic.
I hate
VoIP -
bbocjcp
Actually, you can run modems over IP, but you have to have the DSPs in the voice gateways load in a G.711 codec, disable echo cancellation, and even then you won't get much better than 2400bps.
Why take async data, put in a QAM modulation analogue signal, then put it into an IP packet ?? Just take the Async data and put it straight into an IP packet.
Fax is different, fax is actually T.4/T.6 encoded data, and there are specific codecs designed to take this data and put it into IP packets (hence T.38).
The main issue, is that TDM circuits have a central clock, and not a single packet is lost. VoIP has no such central clock, and the codecs are tuned for human voice, not data. If a Fax sends a checksummed chunk of data, and a single packet is lost in the IP network, the checksum at the other end is wrong. So, the fax resend the message, a packet is lost, etc.
A quick way to mitigate this, is to disable ECM on the fax machines. Cisco Voice gateways can do this, if the end users do not know how to.
If you are having problems with Fax over IP in your network, packet loss is the most likely issue, and disabling ECM will help.
If you have a super G3 fax, with a 33K6 transmission speed, you are hosed, because faxes at that speed are required to use ECM.
For good or bad, I know more about this subject than most people will ever care to know. I don't dip into this forum very much these days, but feel to drop me a note about fax over IP stuff if you are confused by something.
-Conrad
conrad - at bebock.com
Why take async data, put in a QAM modulation analogue signal, then put it into an IP packet ?? Just take the Async data and put it straight into an IP packet.
Fax is different, fax is actually T.4/T.6 encoded data, and there are specific codecs designed to take this data and put it into IP packets (hence T.38).
The main issue, is that TDM circuits have a central clock, and not a single packet is lost. VoIP has no such central clock, and the codecs are tuned for human voice, not data. If a Fax sends a checksummed chunk of data, and a single packet is lost in the IP network, the checksum at the other end is wrong. So, the fax resend the message, a packet is lost, etc.
A quick way to mitigate this, is to disable ECM on the fax machines. Cisco Voice gateways can do this, if the end users do not know how to.
If you are having problems with Fax over IP in your network, packet loss is the most likely issue, and disabling ECM will help.
If you have a super G3 fax, with a 33K6 transmission speed, you are hosed, because faxes at that speed are required to use ECM.
For good or bad, I know more about this subject than most people will ever care to know. I don't dip into this forum very much these days, but feel to drop me a note about fax over IP stuff if you are confused by something.
-Conrad
conrad - at bebock.com
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Pal
Re: T38 FAX over IP
Hi Vad
Where do I set the fax parameter framing to 40ms in the Enterprise.(I'm using G711)
Where do I set the fax parameter framing to 40ms in the Enterprise.(I'm using G711)
