[Freeswitch-users] Major deployment of outbound FAX on latest version of Freeswitch question

[Steve Underwood]

On 05/07/2011 04:02 AM, Andrew Keil wrote:
> Steve,
>
> Thanks for your response.
>
> Further clarification on my part:
>
> 1) 20,000 to 30,000 pages per day to be sent out.
So, this is fairly small scale. A single E1 will do fine.
> 2) It will be an e-mail to fax style gateway (not fax to e-mail since that would involve inbound faxes)
That covers a few requirements, depending what you expect to be in the 
e-mails - send the whole e-mail as a FAX; extract a PDF, Word document, 
etc. from an e-mail, and turn that into a FAX; and so on.
> 3) The reason I asked about e-mail to PDF is the initial comments from my client requested the ability to send PDFs and WORD documents (I guess from attachments to the original e-mail), I understand the format that gets faxed should be TIFF so I saw on the freeswitch wiki email2pdf mentioned.  Then ImageMagick can help get a PDF to TIFF.
If the incoming e-mails are limited to ones containing PDFs and doc 
files to be extracted and turned into FAXes things you seem to have a 
fairly well defined requirement. OpenOffice can be used to turn the doc 
files into FAXable images, but I am not clear how well the newer docx 
files are handled. Ghostscript can be used to turn PDFs into TIFF files.

Avoid ImageMagick for this kind of work. It uses Ghostscript to do the 
hard work, but it doesn't get the best from it. If you use Ghostscript 
directly you get better control, and you can achieve good results.
> Can I ask some more questions:
>
> Q1) Based on your experience what would be the average time (in seconds) to send a single fax page (TIFF file) via Freeswitch&  Sangoma TDM?  You can quote a TIFF file size to make it more accurate.  From there I should be able to do the math to calculate my Client's requirements better.
The time per page depends a lot on its complexity. I use a torture test 
file with images that take half an hour to send. Typical office work is 
probably 20s per page at 14400bps.
> Q2) Running on CentOS and using mod_spandsp/Freeswitch&  Sangoma TDM what percentage CPU usage would I expect to see if 30 concurrent faxes are being sent at the same time (ie. All channels of my E1 are faxing)?  (The hardware would be a new 1U rack server from a major hardware vendor)
The greater part of the CPU load is likely to be what you didn't list 
there - the processing from e-mail to FAXable TIFF files. A single E1 of 
FAXing is a really low load these days, though.
> Q3) What version of CentOS 5.x would you recommend?  Would the latest version 5.6 be fine?
5.6 is fine.
> Q4) From memory there used to be different fax quality modes on fax machines (STANDARD, FINE&  SUPER FINE or something like that).  Is it possible to set the fax send quality from mod_spandsp (also can you provide an example)?  If this is the case could you also answer question (Q1) based on the different fax send quality modes.
You can't really set the quality in mod_spandsp. The quality follows the 
TIFF files to be sent. You can, however, select the image quality as you 
generate the TIFF files in Ghostscript. STANDARD, FINE and SUPERFINE are 
the right names, although many machines refuse to use SUPERFINE.
> Q5) From exisiting deployments of Freeswitch using mod_spandsp (&  Sagoma TDM cards (although this is not critical)) what is the largest number of concurrent outbound faxes done on a single box that you know of?
I'm not sure of the biggest, but an E1 of FAXing is pretty small volume 
these days. The biggest number of channels should be in the hundreds.
> I appreciate your feedback and experience.  It sounds like this will work fine with the mod_spandsp/Freeswitch&  Sangoma TDM combination on CentOS.
>
> I will most likely go for two servers with at least 2 x E1s in each, that way I future proof it a little and add redundancy.  Plus my Client can start using Freeswitch for Voice related services also.  On my side I can also test faxes going out on the first server and via a cross-over cable I can terminate them on the second server (for testing) - much nicer.
>
> Thanks again,
>
> Andrew
Two servers with one E1 in each sounds like more than enough to meet 
your needs, unless your 30k pages per day occur over a fairly short 
working hours, and the customer demands rapid delivery. Then you might 
need more channels to deal with rush hour.

Steve