VOIP fax troubles with OOMA

[FORANE]

We recently converted to OOMA and dropped the landline POTS. OOMA works well provided the internet service isn't down, in which case the phone is also down. Not sure if we have something set incorrectly, but when a call comes in and the line is busy it seems the line will ring for the caller until a fax machine noise is heard by the caller.

We have an OOMA linx and second line set up as a fax line within OOMA but its reliability is terribly poor with maybe 10-20% success rate.

We have considered paying a monthly fee for an online fax service such as one of the following:
http://www.nextivafax.com/index.php
http://www.faxbetter.com/Options.aspx

Are there any current generation fax machines which are compatible with VOIP such as the OOMA?
We currently have a Brother MFC-7860DW fax machine.

What are the good alternatives for fax with a VOIP line? We are low volume with maybe 50 incoming and 50 outgoing pages per month.

 

[Clark1961]

We recently converted to OOMA and dropped the landline POTS. OOMA works well provided the internet service isn't down, in which case the phone is also down. Not sure if we have something set incorrectly, but when a call comes in and the line is busy it seems the line will ring for the caller until a fax machine noise is heard by the caller.

We have an OOMA linx and second line set up as a fax line within OOMA but its reliability is terribly poor with maybe 10-20% success rate.

We have considered paying a monthly fee for an online fax service such as one of the following:
http://www.nextivafax.com/index.php
http://www.faxbetter.com/Options.aspx

Are there any current generation fax machines which are compatible with VOIP such as the OOMA?
We currently have a Brother MFC-7860DW fax machine.

What are the good alternatives for fax with a VOIP line? We are low volume with maybe 50 incoming and 50 outgoing pages per month.

From your first paragraph it sounds like calls are "rolled over" from the first line to the second line if the first line is busy. Once the call is rolled over then the fax machine eventually auto-answers.

As for faxing over VOIP, OOMA sez: http://www.ooma.com/app/support/faxing-ooma

biggies are slowing the fax-data rate and using *99 prefix on outgoing calls.

 

[weilke]

There is some tweaking you or support can do with the settings on the oooma box. Denverpilot gave me great pointers at the time. I got it to work with the fax line on vonage. I then switched yo a hosted pbx aystem and that was the end of my faxing via voip. I now maintain a pots line just for fax and alarm system. Btw, I have the same fax and rvrn on the pots line only 1/2 the faxes get through.

 

[FORANE]

From your first paragraph it sounds like calls are "rolled over" from the first line to the second line if the first line is busy. Once the call is rolled over then the fax machine eventually auto-answers.

As for faxing over VOIP, OOMA sez: http://www.ooma.com/app/support/faxing-ooma

biggies are slowing the fax-data rate and using *99 prefix on outgoing calls.

No, calls are not rolled over from any settings I can find. Suppose it could be doing this; I will look into it. We have 2 separate lines with the OOMA premier service.
One line for voice connected to the OOMA device.
One line for fax connected to the OOMA linx device.
When the voice line is in use and someone else calls in on that line, they eventually get a fax tone after it rings like noone is answering the line not in use.
We have read the link you post and followed the recommendations there to no avail.
Thanks for the post.

There is some tweaking you or support can do with the settings on the oooma box. Denverpilot gave me great pointers at the time. I got it to work with the fax line on vonage. I then switched yo a hosted pbx aystem and that was the end of my faxing via voip. I now maintain a pots line just for fax and alarm system. Btw, I have the same fax and rvrn on the pots line only 1/2 the faxes get through.

When we had the POTS line, we did not have fax trouble. Just were looking to decrease ever increasing costs associated with that line.

 

[weilke]

One line for voice connected to the OOMA device.
One line for fax connected to the OOMA linx device.

The fax line should already be set up as such from ooma. There is something called the 'comfort tone' which is white noise superimposed to the voice signal which is used to fill the awkward silence in conversations. It has to be turned off for fax to work. There are also some encoding algorithms that work better with fax than others. This should be pre-set on a fax line by the voip company, if ooma allows you to play with the settings on the device it may be worth doing that.
Also, if possible, have the device outside of your firewall, there is no need to inspect the packages going to your voip box, depending on the performance of the firewall, it could create packages that are 'out of sequence' and throw off the fax algorithm.

As for the web-fax services: I use myfax for all incoming fax traffic, I rather delete a pdf with a spam fax than paying for toner and paper to print it out. If you have a convenient way to create pdfs (a good scanner), webfax works like a charm for outgoing messages.

 

[FORANE]

The fax line should already be set up as such from ooma. There is something called the 'comfort tone' which is white noise superimposed to the voice signal which is used to fill the awkward silence in conversations. It has to be turned off for fax to work. There are also some encoding algorithms that work better with fax than others. This should be pre-set on a fax line by the voip company, if ooma allows you to play with the settings on the device it may be worth doing that.
Also, if possible, have the device outside of your firewall, there is no need to inspect the packages going to your voip box, depending on the performance of the firewall, it could create packages that are 'out of sequence' and throw off the fax algorithm.

As for the web-fax services: I use myfax for all incoming fax traffic, I rather delete a pdf with a spam fax than paying for toner and paper to print it out. If you have a convenient way to create pdfs (a good scanner), webfax works like a charm for outgoing messages.

Yes, OOMA allows for us to log into the account online and select a setting for the Linx device line optimizing it as a fax line. We have done that, but it has not helped.

Looks like Webfax is just for outgoing fax. Really we need incoming fax more so than outgoing.

I would prefer to just buy a modern fax machine that is VOIP compatible. It does not look like that is available however. I try to avoid ongoing recurring expenses in favor of a single incurred expense; that does not appear to be an option with VOIP/fax.

 

[JGoodish]

My guess is that you are not going to receive reliable fax service from any VoIP provider who does not provide T.38 support.


JKG

 

[PW_Plack]

I had an eFax account for years, worked great. At the time, outgoing fax appeared as one of the printer options, but I think they now have other options, even faxing from a smartphone.

I have Ooma and it's been flawless in every other way.

Ooma is essentially voice sent as data. A fax over Ooma is an image, converted to data, converted to audio by the fax machine, then converted back to data by Ooma...

Get an internet fax service. They work great!

 

[denverpilot]

VoIP + Fax is problematic unless the provider does T.38 and/or allows G.711 as the CODEC for a fax line, and you have almost no packet loss.

Sounds like you've already set the settings at the provider. Check that your fax machine is set to force itself to its LOWEST possible speed. (Usually 9600 bps or 14.4 Kb/s.) Usually buried way down in a menu.

Also if you have control of it, try both with Error Correction turned off and on. Off honestly, will usually work better, even if the image gets a little bit "damaged".

Fax tones (especially at higher speeds) were designed to use up all the audio bandwidth available in an analog circuit designed to carry roughly 0-3000 Hz consistently enough to not cause problems. That equates to a raw data speed of 64 Kb/s, e.g. G.711. Most VoIP providers are compressing the audio path and using CODECs like G.729.

Some chipset manufacturer would probably make a killing if they would just put a device right in the FXS-providing VoIP device that faked out the fax machine into thinking it was talking to the other fax machine, and just properly sending the data from that MODEM direct over the bit-pipe to a similar device at the VoIP provider, or software that mimicked it and didn't carry the tones at all. That's KINDA what T.38 is supposed to do, but not exactly what I'm thinking...

A "dedicated" port on the VoIP device with the modem right in it to talk to the fax machine and fake it out to think it's talking to the far-end fax machine... wouldn't really be that hard to implement. Fix a lot of problems for a lot of folks...

I'm also surprised someone hasn't just made a standard for Fax over Ethernet and been done with putting modems in Fax machines altogether... really it's just scanning and uploading a file, in the end... but since government, financial, and other entities still treat the fax machine like it's somehow superior to other forms of scanning and uploading... especially in a legal sense... it's weird... might as well play along.

Dunno. The problem is it's all at commodity price points nowadays... "fixing" the home phone line to do fax, isn't high on anyone's list because it is a money-loser.

 

[DaleB]

Huh. I guess I'm glad I did this before Ooma and the others came along.

I've been using VOIP exclusively for a couple of years now for my work (100% telecommuter) and for my side business. I recently went ahead and ported our home number over and canceled the POTS phone line.

FAX has been a non-issue the whole time. At first I used the FAX machine attached to an analog card (A400 FXO/FXS 4-port card) in the Asterisk server. Later on I installed iaxmodem and HylaFAX, with an email/FAX and FAX/email gateway. We haven't used the FAX machine (actually a multifunction Lexmark machine) in ages - I need to donate or sell it. Anything that needs to be scanned we scan with a little hand scanner or my wife's flatbed. After that it's a simple matter of emailing the image to "<faxnumber>@fax.out", which gets sent as a FAX via the VOIP service. Works every time. Incoming FAX calls to any number are automatically detected, received and delivered to our email.

All the work is done by a combination of Linux, Postfix, Asterisk and HylaFAX. It did take a few hours' work to set up the first time and get it working the way it should, but since then it's been rock stable for those very few times we need to use it. Nearly everyone now is comfortable with emailed PDF or images, so I'm glad it doesn't cost us a cent to handle faxes. I think my total cost of telecom over a typical month (that's three regular numbers and one toll free) is now under $10. The analog line alone was costing us something like $35 after all the taxes and tacked-on fees.

Next project: Setting up a Raspberry Pi with Asterisk as a failover, just in case the server blows up.

 

[FORANE]

Huh. I guess I'm glad I did this before Ooma and the others came along.

I've been using VOIP exclusively for a couple of years now for my work (100% telecommuter) and for my side business. I recently went ahead and ported our home number over and canceled the POTS phone line.

FAX has been a non-issue the whole time. At first I used the FAX machine attached to an analog card (A400 FXO/FXS 4-port card) in the Asterisk server. Later on I installed iaxmodem and HylaFAX, with an email/FAX and FAX/email gateway. We haven't used the FAX machine (actually a multifunction Lexmark machine) in ages - I need to donate or sell it. Anything that needs to be scanned we scan with a little hand scanner or my wife's flatbed. After that it's a simple matter of emailing the image to "<faxnumber>@fax.out", which gets sent as a FAX via the VOIP service. Works every time. Incoming FAX calls to any number are automatically detected, received and delivered to our email.

All the work is done by a combination of Linux, Postfix, Asterisk and HylaFAX. It did take a few hours' work to set up the first time and get it working the way it should, but since then it's been rock stable for those very few times we need to use it. Nearly everyone now is comfortable with emailed PDF or images, so I'm glad it doesn't cost us a cent to handle faxes. I think my total cost of telecom over a typical month (that's three regular numbers and one toll free) is now under $10. The analog line alone was costing us something like $35 after all the taxes and tacked-on fees.

Next project: Setting up a Raspberry Pi with Asterisk as a failover, just in case the server blows up.

This looks like English, but I am not sure.

 

[DaleB]

It ain't easy being geek.

 

[denverpilot]

Huh. I guess I'm glad I did this before Ooma and the others came along.

What CODEC are you using for your SIP trunks? I suspect G.711.

My answers were aimed at those who are using "consumer" ATAs provided by their SIP provider. Most are using G.729 which just compresses the audio too much to have reliable faxing over it.

Asterisk on a Raspberry Pi is on my "whenever I finally get some free time" list. We use so much Asterisk at work, I am not very motivated to play with it at home. I'd much rather go flying or shooting.

Hell, I'd rather walk the dog.

Some doofuses at Corporate attempted a back-door coup once they realized they bought a small company using Asterisk instead of their beloved Avaya gear.

A recent all-hands meeting proved that while the VP would be politically correct and say they'd continue to "evaluate all options", rumor is that their $3M price tag and never ending licensing costs per seat vs our roughly $5K per server for T1 and $3K per server for SIP, probably means that the Avaya cabal's stupid little end-run was DOA before they even started it.

They're feeling threatened. Probably should with numbers like that.

 

[DaleB]

Yes, G.711. It works great, and with no more than a couple of calls over a halfway decent cable modem connection there's certainly no bandwidth issue. Besides, G.729 costs money and I'm cheap.

I briefly tried a Pi FreePBX distribution, and quickly realized that I'd much rather configure Asterisk by hand. I can just scp my config files over and do some minor editing. That's the easy part. I want automatic, no-intervention failover; that will be the hard part.

I would not want to be Avaya or Nortel. If they don't feel like Fox Photo (remember them?) right now, they should. I think the only reason they still have any business left at all may be because there are companies that just haven't hired anyone who knows about Asterisk.

 

[JGoodish]

In my experience, most residential-grade VoIP providers actually default to a codec such as G.726, as G.729 requires licensing. Even with G.711, it is unlikely that any of these providers are going to deliver reliable fax performance.


JKG

 

[JGoodish]

I would not want to be Avaya or Nortel. If they don't feel like Fox Photo (remember them?) right now, they should. I think the only reason they still have any business left at all may be because there are companies that just haven't hired anyone who knows about Asterisk.

Nortel is long gone, owing their demise to years of scandal and mismanagement, not to competition from open-source software. Both Avaya and Cisco market systems which far outclass anything based on Asterisk or FreeSwitch, though that doesn't mean that such systems are a better solution for every use case.


JKG

 

[weilke]

In my experience, most residential-grade VoIP providers actually default to a codec such as G.726, as G.729 requires licensing. Even with G.711, it is unlikely that any of these providers are going to deliver reliable fax performance.

As a I said, it works without a problem on my vonage box. Both on the 'voice' line and when I had their 'free' fax-line on the business account.

 

[denverpilot]

In my experience, most residential-grade VoIP providers actually default to a codec such as G.726, as G.729 requires licensing. Even with G.711, it is unlikely that any of these providers are going to deliver reliable fax performance.

G.711 over a loss-less circuit is indistinguishable from a standard POTS line. Nyquist kinda created this law about sampling rates...

 

[denverpilot]

Nortel is long gone, owing their demise to years of scandal and mismanagement, not to competition from open-source software. Both Avaya and Cisco market systems which far outclass anything based on Asterisk or FreeSwitch, though that doesn't mean that such systems are a better solution for every use case.

Nah, not that gone. Ericsson bought up most of the useful stuff. They just didn't quite get the timing right on their bankruptcy car wash. Like most telecom and networking manufacturers, their leadership got away with illegal book cooking. Nortel just got caught.

 

[JGoodish]

G.711 over a loss-less circuit is indistinguishable from a standard POTS line. Nyquist kinda created this law about sampling rates...

The codec is only part of the equation. The reliable transmission of fax (or voice, for that matter) depends on much more than just the codec.


JKG

 

[JGoodish]

Nah, not that gone. Ericsson bought up most of the useful stuff. They just didn't quite get the timing right on their bankruptcy car wash. Like most telecom and networking manufacturers, their leadership got away with illegal book cooking. Nortel just got caught.

Nortel ceased business operations nearly 5 years ago, and their patents and business units were sold off to various entities. Avaya acquired their telephony assets, for which they were perhaps best known.

Accounting irregularities were only a symptom of Nortel's troubles. Nortel acquired top-shelf technology over the years, but demonstrated a habitual ineptitude with respect to development and marketing of that technology. As is the case with many companies, they made some large acquisitions that distracted from their core competency, and they were never able to recover from those mistakes.


JKG

 

[weilke]

Our last Nortel VPN firewall is shutting down this week. There were still about 50 people in the company who apparently haven't upgraded their computer in 5 years .

 

[JGoodish]

As a I said, it works without a problem on my vonage box. Both on the 'voice' line and when I had their 'free' fax-line on the business account.

If they are marketing a fax line with any claim of reliability, I suspect that they are employing some type of T.38 relay architecture to deliver the service.

I've been using VoIP providers for my residential phone line(s) for at least 6 years now, using different codecs (mostly G.711), and reliability even for voice has been a crapshoot. When I look back over the past 6-7 years, the performance has been generally underwhelming, at a reduced but still rather high cost over PSTN lines when performance is considered. Migrating to my own Asterisk server trunked to a wholesale SIP provider has resulted in substantially better service at a much lower cost.


JKG

 

[DaleB]

I've been using VoIP providers for my residential phone line(s) for at least 6 years now, using different codecs (mostly G.711), and reliability even for voice has been a crapshoot. When I look back over the past 6-7 years, the performance has been generally underwhelming, at a reduced but still rather high cost over PSTN lines when performance is considered. Migrating to my own Asterisk server trunked to a wholesale SIP provider has resulted in substantially better service at a much lower cost.

I was wondering what was wrong with your Internet connection until I read that last sentence. I've been tickled pink with the performance (Asterisk) and cost (Flowroute) of my VOIP setup, and I'm really picky.

 

[weilke]

If they are marketing a fax line with any claim of reliability, I suspect that they are employing some type of T.38 relay architecture to deliver the service.

I've been using VoIP providers for my residential phone line(s) for at least 6 years now, using different codecs (mostly G.711), and reliability even for voice has been a crapshoot. When I look back over the past 6-7 years, the performance has been generally underwhelming, at a reduced but still rather high cost over PSTN lines when performance is considered. Migrating to my own Asterisk server trunked to a wholesale SIP provider has resulted in substantially better service at a much lower cost.


JKG

I can't complain about vonage. I used to have a dedicated 'fax line' on the business account and it worked with a hp MFP. On the home phone I use the voice line with a older panasonic fax also without issues.

 

[wsuffa]

I would not want to be Avaya or Nortel. If they don't feel like Fox Photo (remember them?) right now, they should. I think the only reason they still have any business left at all may be because there are companies that just haven't hired anyone who knows about Asterisk.

Nah, at least not for Avaya or Cisco. Too many big companies wedded to expensive, big-name options because it's the "safe" decision. Same reason that IBM still has a lot of business. And same reason that Verizon and AT&T continue to charge exhorbinant rates - even witht he MVNOs operating on their networks.

Corporate America.

I will tell you sometime about the company that budgeted $10,000 per employee to replace every computer (regardless of age) in a company that they acquired - just so they could be on the "company standard".

 

[DaleB]

Nah, at least not for Avaya or Cisco. Too many big companies wedded to expensive, big-name options because it's the "safe" decision. Same reason that IBM still has a lot of business. And same reason that Verizon and AT&T continue to charge exhorbinant rates - even witht he MVNOs operating on their networks.

Corporate America.

You know, you'd think that... but Sun felt the exact same way about "that cheap Intel hardware" and Linux not that many years ago. It didn't work out so well for them.

 

[wsuffa]

You know, you'd think that... but Sun felt the exact same way about "that cheap Intel hardware" and Linux not that many years ago. It didn't work out so well for them.

Difference is that Sun was a vendor view - I'm talking customer view. At the time wintel hardware offered more options for software & centralized desktop management compared to Sun. Linux is making headway, but in most corporations you'll still not find much Linux deployment compared to wintel (or Apple). And IBM had an awful lot to do with wintel deployment at large companies.

 

[DaleB]

Difference is that Sun was a vendor view - I'm talking customer view. At the time wintel hardware offered more options for software & centralized desktop management compared to Sun. Linux is making headway, but in most corporations you'll still not find much Linux deployment compared to wintel (or Apple). And IBM had an awful lot to do with wintel deployment at large companies.

Apple? Now I know you're kidding. The Linux server population at my company is in the tens of thousands, about 2/3 the number of Windows servers and gaining ground. Solaris -- I think there may be a couple hundred left. Apple? Zero, as far as I know. Of course when I say "server" that means, about 80% of the time, a virtual server.

At the last place I worked, we were 100% Sun in the data center when I got there... about 25% Sun when I left, the rest replaced with Linux on Intel machines from a combination of HP/Compaq, IBM and Dell. That was a while ago; I heard they replaced the Fujitsu/Solaris back end systems with a few racks of Intel/Linux servers.

Sun thought they were invincible, customers would keep buying Sun hardware and Solaris just because -- well, they were Sun, after all. They failed to adapt, in any meaningful way, to the progress of technology outside their door.

I will readily admit that I don't know nearly as much about telecom systems as I do servers; I didn't even remember Nortel was long dead (I had heard that, but forgot it). I don't work in that field. I'm sure that especially for the higher end systems, they will continue to hang on for years to come. But it's undeniable that a whole lot of companies that would once have been forced to call a manufacturer of a proprietary system now have the choice of a far less expensive open system, and the number of them making that choice is growing. Like I said... if I were selling a proprietary PBX I'd be looking over my shoulder and starting to sweat a little.

 

[wsuffa]

Apple? Now I know you're kidding. The Linux server population at my company is in the tens of thousands, about 2/3 the number of Windows servers and gaining ground. Solaris -- I think there may be a couple hundred left. Apple? Zero, as far as I know. Of course when I say "server" that means, about 80% of the time, a virtual server.

At the last place I worked, we were 100% Sun in the data center when I got there... about 25% Sun when I left, the rest replaced with Linux on Intel machines from a combination of HP/Compaq, IBM and Dell. That was a while ago; I heard they replaced the Fujitsu/Solaris back end systems with a few racks of Intel/Linux servers.

Sun thought they were invincible, customers would keep buying Sun hardware and Solaris just because -- well, they were Sun, after all. They failed to adapt, in any meaningful way, to the progress of technology outside their door.

I will readily admit that I don't know nearly as much about telecom systems as I do servers; I didn't even remember Nortel was long dead (I had heard that, but forgot it). I don't work in that field. I'm sure that especially for the higher end systems, they will continue to hang on for years to come. But it's undeniable that a whole lot of companies that would once have been forced to call a manufacturer of a proprietary system now have the choice of a far less expensive open system, and the number of them making that choice is growing. Like I said... if I were selling a proprietary PBX I'd be looking over my shoulder and starting to sweat a little.

You're talking servers, I'm talking desktops and workstations.

Yeah, Linux has pretty good penetration on servers. Sun went the way of Novell - lack of innovation and being supplanted by stuff that was more open and capable.

But yes, on Telecom, it's not seen quite the same way as server systems, and the life-cycle of your typical PBX is considerably longer than your average server. Some change has come, though - I don't know *anyone* using Centrex these days.

 

[denverpilot]

The codec is only part of the equation. The reliable transmission of fax (or voice, for that matter) depends on much more than just the codec.

You don't read real well, do you?

I clearly stated that on a lossless typical IP circuit (oh maybe I should add "terrestrial" in case some doofus wants to talk about delay) G.711 will pass fax audio just fine.

Christ. Ricoh was doing faxing on ****ty noisy analog circuits to the North Slope in the 1970s.

Fax isn't that hard. It just won't cram through a lossy audio CODEC. You and I could babble on about stupid crap like jitter and group delay, and it has virtually no bearing on the question posed by the person using a residential VoIP provider.

One of the many server farms from my past was a bulk faxing system for investor relations press releases, when most of the world barely had modems... thankfully US Robotics and Motorola had audio engineers worth a crap back then, since most of the others didn't... Or that system would have been a nightmare from hell.

Anyway, answers are still correct. For a modern home / typical small biz VoIP setup, your best chance of a fax machine working through the "phone line" is G.711 and set the machine to 9600 baud and lock it there. Better, is if your provider does T.38 or otherwise conditions the circuit for faxing. Best is just scan and email the stupid thing.

Taking a scanner, stuffing the data output through a modem into a VoIP ATA, converting back to data, passing to a provider who then converts it back to audio, over a DS0 and through the PSTN (who probably converts it back to SIP and G.771 *again* inside their backbone! especially if it's VZ), and then out to a fax machine on the other end which may be hooked to a real POTS line, or may be doing as much silliness as the sending end... Is essentially a losing battle. Too many D-to-A and A-to-D conversions in the chain anymore.

The analog PSTN is dead, long live the analog PSTN!

 

[denverpilot]

I have a t-shirt...

Linux for servers
Apple for desktop
Microsoft for Solitaire

 

[JGoodish]

You don't read real well, do you?

I do, and I also appear to have far more experience with VoIP design and operation than you do.


JKG

 

[FORANE]

eh, why do these threads deteriorate into personal assaults?

I guess the answer to the subject of the thread is either:
1: keep old phone line
2: sign up for internet fax service

 

[denverpilot]

I do, and I also appear to have far more experience with VoIP design and operation than you do.





JKG

That's so cute that you actually think so.

I always get a kick out of people on the Net who post stuff like that.

"I am The Master of the Universe!"

Nothing else, no useful information, nothing related to the discussion, just raw ego. LOL.

It's quite entertaining.

As for the person who was concerned about personal insults...

Stating "I'm awesome, smell me! I have experience!" on the Internet -- is of more comedic value to me, than anything.

 

[rpadula]

Stating "I'm awesome, smell me! I have experience!" on the Internet -- is of more comedic value to me, than anything.

Nate, my friend, prepare to inhale deeply. BTW, I have significant design experience in DSP and both FXO & FXS POTS (with just enough gray hairs to have worked with circuit-switched systems before moving to VoIP), and have troubleshot more modem/fax-over-IP issues than I would like to admit. My favorite was the gateway that turned the echo cancelers back on and changed the loss plan in the middle of a call, but I digress. I agree with JGoodish, when he said it takes more than the right codec for successful VoIP faxing.

In my experience, most residential-grade VoIP providers actually default to a codec such as G.726, as G.729 requires licensing. Even with G.711, it is unlikely that any of these providers are going to deliver reliable fax performance.

JKG

G.711 over a loss-less circuit is indistinguishable from a standard POTS line. Nyquist kinda created this law about sampling rates...

…and Nyquist has nothing to do with the issue, as G.711, G.726, and G.729 all sample at 8 kHz. Nothing to see here.

I will not pick on some of your other inaccuracies, nor quote more inner workings of faxing. Your argument thrice boiled down to this:

G.711 over a loss-less circuit is indistinguishable from a standard POTS line. Nyquist kinda created this law about sampling rates...

VoIP + Fax is problematic unless the provider does T.38 and/or allows G.711 as the CODEC for a fax line, and you have almost no packet loss.

You don't read real well, do you?

I clearly stated that on a lossless typical IP circuit (oh maybe I should add "terrestrial" in case some doofus wants to talk about delay) G.711 will pass fax audio just fine.
…snip...
Fax isn't that hard. It just won't cram through a lossy audio CODEC. You and I could babble on about stupid crap like jitter and group delay, and it has virtually no bearing on the question posed by the person using a residential VoIP provider.

Lossless connections only exist in textbooks. Throw your VoIP packets to the public internet, and all bets are off!

The v.xx modem schemes took advantage of certain properties of the constant bitrate circuit-switched network that VoIP can only emulate the best it can. Lose one packet, and your minimum loss is 160 "voice" samples at the typical 20 msec packet rate. If you're lucky and packetizing at 10 msec rates, you'll only lose 80 samples. This is huge compared to the traditional telephone system BER. And if one gets stuck behind others long enough or gets routed to east BFE and shows up late, it's as good as lost.

Have a look at this Dialogic whitepaper on Fax over IP. It doesn't take much packet loss at all to absolutely crater fax performance.

Anyway, answers are still correct. For a modern home / typical small biz VoIP setup, your best chance of a fax machine working through the "phone line" is G.711 and set the machine to 9600 baud and lock it there. Better, is if your provider does T.38 or otherwise conditions the circuit for faxing.

Your answers are helpful, but the professors always made us show our work, too, to ensure full credit.

 

[denverpilot]

Sigh. Saying lossless networks don't exist, is disingenuous. Some paths on some residential networks to some providers really are essentially lossless.

I have seen the Dialogic white paper. It's obviously biased, since they're still selling their fax stuff they created back before they were bought by Intel and all the really brilliant people cashed out and left. Surprised me to see a 2011 copyright on it. Same paper was out over ten years ago. If you note carefully that they turned off ECM and put a vague (paraphrased) "with ECM completion rates were higher but the image was [in Dialogic's view, but not quantified and no examples shown, of course! because in many people's view the quality would have been fine for a simple document] unacceptably distorted".

If you look back at my sentence about Nyquist it's specifically talking about the resulting output of a lossless codec. Sampling at 8 KHz means absolutely bupkis if you're going to stuff it through a lossy codec instantly thereafter. The point was, that sampled at 8 KHz and left alone, fax tones will pass adequately through that, just fine.

Shoving that lossless codec through a packet loss filled network, sure... that'll suck.

We can sit here and quote textbooks all we like. The original question was, "Can I hook my fax up and have it work on a typical residential VoIP provider. And the answer was a complex... Maybe. And that's still true.

Your provider needs to not be using a lossy codec and/or you need a handle to pull to "change the voice quality" as an end user. Some providers are conscientious enough to provide it. They usually call it "bandwidth saver" or similar. All they're doing is telling their gear to negotiate G.711 on the high end of that end user setting for high bandwidth. (No one is offering it commercially as a residential service, but the so-called "HD" codecs will happily pass fax also. Typically only seen in business service on private networks, since carriers are cheap. Better audio quality than the old PSTN is not a goal that any residential provider usually shoots for or offers, since their head end bandwidth requirements go higher and their bottom of the barrel commodity prices won't allow them a profit using those.)

As far as the snarky "show your work" crap, it's an aviation Internet forum and the replies are tailored to the question. I'm not writing a damn engineering document explaining 20 years of VoIP to answer "can I make my fax machine work?" Kinda stupid waste of time, honestly. Folks asking "Will running my O-470 work LoP?" have the same types of never-ending threads come up, and the conclusion is always similar... "Go try it. Maybe. Some do, most don't. Not designed for it."

A scanner and an email is far smarter, but some businesses still think fax machines are the cat's meow. And Courts strangely still accept them over most digital documents, but that's been rapidly changing for a number of years now.

Best advice: Dump using the fax machine. But that's not the question the OP asked.

Second best advice: Let some other idiot go broke building bulk faxing tech (the money went out of that industry a looooong time ago, but it was fun back when bulk faxing investor relations documents Net'd $10M a year as a side business... Yeah, Net. Not Gross.) and use their service, but you'll have to pay a little for it. Inbound they receive and email to you, outbound you scan and send to them and they fax it. Basically let someone else pay to maintain the history museum. Heh.

Last resort advice: Set your "bandwidth" or "voice quality" setting as high as it will go on a commercial residential VoIP vendor's user interface and try it. The quality will probably be acceptable for one-off faxing when someone thinks they need you to. Force the fax machine to 9600 baud in the menu and ECM on and give it a shot. It often works.

Dialogic paper was a nice touch, but like I said, they're horribly biased. They're still selling cards they designed in the 90s. They did new versions of them to replace components not available after RoHS, but they're not innovators anymore.

(Side note: Want to see a disaster of BER? Install multiple Dialogic T1 cards in the same computer and feed them from different carriers and ask Dialogic how to make the clocks line up. Heh. They're not carrier class and never will be. But, they're cheap and meet the 80/20 rule for things people buy their stuff to do. Similarly early Cisco stuff was a clocking disaster too, but at least they invested in telecom engineers to clean up their crap eventually... with an appropriate increase in price tag...)

 

[rpadula]

Snarky? Good heavens, no. I said your answers were helpful. The bit about professors was tongue-in-cheek; Mr. Winkey-face icon made it so.

Pardon me.

 

[denverpilot]

Snarky? Good heavens, no. I said your answers were helpful. The bit about professors was tongue-in-cheek; Mr. Winkey-face icon made it so.

Pardon me.

Ahh sorry. The joys of typed communication with no verbal or visual clues bites again...