On 05/09/2011 08:18 AM, Steve Underwood wrote:
On 05/09/2011 01:16 AM, Juan Antonio Ibañez Santorum wrote:
How much reliable FS + mod_spandsp is compared to other solutions (open source or not)? The open source options are:
Asterisk + spandsp Asterisk + Hylafax + iaxmodem + spandsp Freeswitch
These are all tested and proven to give well below 1% failures, even with quite a lot of concurrent FAX channels in use, if things are set up well. They can give you bad failure rates if things are not set up well. I believe that right now you will have less trouble achieving a reliable setup with Freeswitch. Going forward, most of my effort goes into making the Freeswitch option the most thoroughly implemented one.
The main commercial option is:
Asterisk + Digium's commercial FAX
Of course, there are numerous other fully commercial FAXing options which could be used in conjunction with things like Asterisk or Freeswitch
The Digium FAX module is based on the well known Commetrex FAX engine, which is widely deployed, and should be capable of solid results. However, the module is more than just the core FAX engine, and some people do have serious trouble with the module. I have helped moved people off this, and onto Asterisk + spandsp, to improve their reliability. In a couple of those cases people were getting quite a lot of pages cut short when receiving FAXes with T.38, even though a wireshark log showed a perfect exchange, from which I could correctly decode these FAXes. The module was not reporting any errors. In a couple of cases strange machines were sending weird things the Digium FAX didn't cope with very well. I worked with these people to make sure spandsp did handle the weird stuff well, and we ended up with a more usable solution. These people told me that when they complained to Digium they got little help. The best was an offer of a refund. Paying to get some support didn't seem to work out too well for these people, but I guess if the support you are looking for is mostly in getting things configured and working on day one you might get value for money.
All these solutions require reliable signaling and reliable media timing, and many people have setups which cannot achieve that. Most people don't understand how things work, and will claim a solution doesn't function for spurious reasons. For example, a number of people say the spandsp module for Asterisk doesn't work, because they keep getting a 488 response. That response has nothing to do with the FAX engine. It is a negotiation error that occurs outside the FAX engine. If they fixed their configuration the error would go away. However, many just move on, having "proven" to themselves the solution doesn't work.
I forgot one important point. Right now, the only out of the box solution for T.38 gateway is Freeswitch. There are patches in the Digium bugtracker to add T.38 gateway functionality, but its not in the software distribution. They seem to be seriously working on T.38 gateway for a future release of Asterisk. I don't know if there will be a commercial T.38 gateway from Digium. It looks like all their current work is with spandsp. Steve