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

Sun May 8 21:16:18 MSD 2011

How much reliable FS + mod_spandsp is compared to other solutions (open
source or not)?

2011/5/8 Steve Underwood <steveu at coppice.org>

> 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
>
>
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