Tips for Using Fax More Efficiently over VoIP by Nitzan Kon
So, you're contemplating about ditching that POTS in favor of VoIP? So far so good... but what about that fax machine that's sitting there, lonely in the corner? is it going to play nice with the new technology? The short answer is "No". The long answer is "it's complicated"...
To put things into perspective, a fax machine basically needs several things to operate successfuly:
1. An analog telephone signal.
2. Enough bandwidth to send the data over.
3. No broken signals or interupptions
The problem(s) with Faxing over IP are precisely those:
1. VoIP carries a digital signal - not an analog one.
2. More often than not, the codecs used in VoIP do not provide the fax with enough bandwidth to transmit over.
3. With VoIP it is possible and even likely that some data signals will get "lost" before reaching the remote machine. When carrying a voice call this is not an issue since we (humans) do not hear the subtle difference that one lost packet represents. Fax machines, are far more senstive (one could say grouchy) than us humans. If they don't get their data exactly as they expect it, they throw a temper tantrum and abort the transmission.
For these reasons, trying to fax over IP is a daunting task indeed. Even with the best of internet pipes you're still expecting a 70% success rate - if you're lucky.
Alright, enough with the bad news, let's go back to what this article is about - helping you achieve the best results you can with your faxes and Voice over IP connection! For purposes of illustration, we're going to describe settings for Linksys Analog Telephone Adapters. Some of the steps described below will work with other makes too though. Alright, let's get started!
1. Set your codec to G711u (ulaw). Why? because G711 is the only codec with enough bandwidth to simulate a "real" phone line's bandwidth.
2. Set your RTP Packet Size to 0.020, or even 0.010. This value is essentially a measurement of how much time in milliseconds will be contained in each voice packet. You are going to lose voice packets - that is a given - but the smaller the lost packets are, the better the chance is that your fax will be able to recover from the error.
3. Stop all uploads. You have a 15/5mbit connection? good for you, now stop that p2p client - and don't even think of the word "video" until your transmission is done. Even the most subtle interference will cause you problems, so do yourself a favor and just stop all traffic ahead of time.
4. This is a bit counter-intuitive, but turn off ECM (error correction) on your fax. ECM is great for error correction on POTS, doesn't play well over IP.
5. Decrease the transfer speed on your fax. Some machines will call this "overseas mode", and some will just have an option to lower the speed. Either way you want to use the lowest speed possible and definitely under 9600 bps. Why? we go back to our first point - bandwidth. The best way to counter limited bandwidth is to, well, not use bandwidth.
6. Put a DSL filter between your fax machine and your ATA.
7. Try to avoid faxing long documents. Try to fax pages in bunches of 2-3 at most to maximize chances of success. The longer the fax session is, the higher the likelihood you're going to run into a problem.
8. Disable echo cancelation in your ATA. You probably want to keep echo cancelation on when you're making voice calls, but your fax cares less about echo and more about getting an accurate signal. A recommended approach to handle this is to use echo cancelation on Line 1 - but disable it on Line 2.
9. Disable silence suppression. Silence suppression is one of those catch phrases that had a lot of hype behind them due to bandwidth being saved. But in order to save the little bandwidth that you do, you sacrifice both voice quality and signal clarity. Your faxes are definitely not going to approve.
10. Set Codec Symmetric to No.
11. Set Passthrough Method to ReINVITE.
12. Set FXS Port Input Gain and FXS Port Output Gain to -3. (this is the default for Linksys adapters)
If you follow these steps, and pray a little, you are guaranteed... well, you're not guaranteed anything. Faxing over IP will still be totally hit-or-miss, but your chances will go from 0% to something much higher than that. My advice is that if you do serious faxing for your business, and particularly if your business depends on it - do yourself a favor and keep that land line. After all- if you've read some of my other articles, you already know that you should keep at least one land line for proper 911 availability!
Nitzan Kon is the CEO of Future Nine Corp - a leading Cheap Phone Service Provider, who also specializes in Callings Cards driven by Voice over IP.
Article Source: ArticleSnatch Free Article Directory
So, you're contemplating about ditching that POTS in favor of VoIP? So far so good... but what about that fax machine that's sitting there, lonely in the corner? is it going to play nice with the new technology? The short answer is "No". The long answer is "it's complicated"...
To put things into perspective, a fax machine basically needs several things to operate successfuly:
1. An analog telephone signal.
2. Enough bandwidth to send the data over.
3. No broken signals or interupptions
The problem(s) with Faxing over IP are precisely those:
1. VoIP carries a digital signal - not an analog one.
2. More often than not, the codecs used in VoIP do not provide the fax with enough bandwidth to transmit over.
3. With VoIP it is possible and even likely that some data signals will get "lost" before reaching the remote machine. When carrying a voice call this is not an issue since we (humans) do not hear the subtle difference that one lost packet represents. Fax machines, are far more senstive (one could say grouchy) than us humans. If they don't get their data exactly as they expect it, they throw a temper tantrum and abort the transmission.
For these reasons, trying to fax over IP is a daunting task indeed. Even with the best of internet pipes you're still expecting a 70% success rate - if you're lucky.
Alright, enough with the bad news, let's go back to what this article is about - helping you achieve the best results you can with your faxes and Voice over IP connection! For purposes of illustration, we're going to describe settings for Linksys Analog Telephone Adapters. Some of the steps described below will work with other makes too though. Alright, let's get started!
1. Set your codec to G711u (ulaw). Why? because G711 is the only codec with enough bandwidth to simulate a "real" phone line's bandwidth.
2. Set your RTP Packet Size to 0.020, or even 0.010. This value is essentially a measurement of how much time in milliseconds will be contained in each voice packet. You are going to lose voice packets - that is a given - but the smaller the lost packets are, the better the chance is that your fax will be able to recover from the error.
3. Stop all uploads. You have a 15/5mbit connection? good for you, now stop that p2p client - and don't even think of the word "video" until your transmission is done. Even the most subtle interference will cause you problems, so do yourself a favor and just stop all traffic ahead of time.
4. This is a bit counter-intuitive, but turn off ECM (error correction) on your fax. ECM is great for error correction on POTS, doesn't play well over IP.
5. Decrease the transfer speed on your fax. Some machines will call this "overseas mode", and some will just have an option to lower the speed. Either way you want to use the lowest speed possible and definitely under 9600 bps. Why? we go back to our first point - bandwidth. The best way to counter limited bandwidth is to, well, not use bandwidth.
6. Put a DSL filter between your fax machine and your ATA.
7. Try to avoid faxing long documents. Try to fax pages in bunches of 2-3 at most to maximize chances of success. The longer the fax session is, the higher the likelihood you're going to run into a problem.
8. Disable echo cancelation in your ATA. You probably want to keep echo cancelation on when you're making voice calls, but your fax cares less about echo and more about getting an accurate signal. A recommended approach to handle this is to use echo cancelation on Line 1 - but disable it on Line 2.
9. Disable silence suppression. Silence suppression is one of those catch phrases that had a lot of hype behind them due to bandwidth being saved. But in order to save the little bandwidth that you do, you sacrifice both voice quality and signal clarity. Your faxes are definitely not going to approve.
10. Set Codec Symmetric to No.
11. Set Passthrough Method to ReINVITE.
12. Set FXS Port Input Gain and FXS Port Output Gain to -3. (this is the default for Linksys adapters)
If you follow these steps, and pray a little, you are guaranteed... well, you're not guaranteed anything. Faxing over IP will still be totally hit-or-miss, but your chances will go from 0% to something much higher than that. My advice is that if you do serious faxing for your business, and particularly if your business depends on it - do yourself a favor and keep that land line. After all- if you've read some of my other articles, you already know that you should keep at least one land line for proper 911 availability!
Nitzan Kon is the CEO of Future Nine Corp - a leading Cheap Phone Service Provider, who also specializes in Callings Cards driven by Voice over IP.
Article Source: ArticleSnatch Free Article Directory