[asterisk-users] Ast/Hyla/IAX Scalability?

[Stephen Davies]

Hi,

I know i doesn't make practical difference, but often it is the far
end that is atually buggy,  not out end.

A lot of the work in spandsp to increase success rate is to do with
workarounds for issues in the remote machine,

Steve

On 3/13/09, Marshall Henderson <marshallmch at gmail.com> wrote:
> On Fri, Mar 13, 2009 at 11:07 AM, David Backeberg <dbackeberg at gmail.com>
> wrote:
>>
>> On Fri, Mar 13, 2009 at 11:38 AM, Marshall Henderson
>> <marshallmch at gmail.com> wrote:
>> > I recently read the thread entitled "Faxing Success Rate on PRI" which
>> > dealt
>> > with Asterisk/HylaFax/IAXmodem. I'm successfully using this 'recipe' in
>> > a
>> > few instances on systems with only a couple of analog lines all the way
>> > up
>> > to a full PRI worth of Iaxmodems.
>>
>> Then you have probably seen that YMMD, and that some people claim
>> great success with VoIP fax.
>>
>> Other people claim that the only way to go is a hardware fax solution,
>> like the dedicated multi-modem fax cards.
>>
>> The only way you're going to find a solution that will work for you is
>> to try it, scale it, build your own expertise with your solution, load
>> test it, and watch your error rate.
>>
>
> I certainly understand the value of building the solution, testing,
> patching,  and fixing problems as they arise. It was my hope however
> that others would have large-scale experience with these technologies
> and could share some pointers.
>
> I'm about to perform some bulk testing between two servers to see how
> the system reacts. I'm more than happy to post my findings here if
> anyone has interest.
>
>> The other consideration is your budget and your cost of dropping a
>> fax. The faxmodem cards are not cheap compared to a voip solution. But
>> if the faxes have a high value to the business the hardware cards are
>> probably justified.
>>
>> Again, you'll find people arguing that their voip solution has as low
>> of a failure rate as a hardware solution. I'm jealous. My voip fax
>> solution does not yet have that low of a failure rate, but I'm
>> hopefully getting closer to working out the last bugs.
>>
>
> Do you have any specifics to share about the problems you're finding?
>
>> > I've also noticed that IAXmodem is compiled statically against a version
>> > of
>> > spandsp included with the iaxmodem source. For a large installation,
>> > would
>> > it be better to compile iaxmodem dynamically to reduce the per-instance
>> > size
>> > of each iaxmodem? Or, would it be better to simply throw more RAM at it?
>>
>> I'm not sure what difference RAM makes. What breaks a fax on voip is
>> latency and dropped packets.
>
> Agreed. I was simply inquiring about the efficiency of IAXmodem at the
> system resource level. Latency and packet drops will be minimal or
> nonexistent at all in this environment.
>
>>
>> You solve both of those problems if you go the hardware solution route
>> with a faxmodem card.
>>
>
> I've found hardware fax boards aren't a 100% fix either. Many of the
> boards are buggy. However, I will have to say that certain
> manufacturers like Mainpine are near 100%.
>
>> The in-between solution is using a proprietary telco -> fax gateway,
>> like a Cisco box that terminates a PRI and provides FXO ports that you
>> plug into a single-pair faxmodem or a 'real' fax machine. That
>> solution quickly becomes ridiculous when you try to scale it.
>>
>> > Are there any concurrency issues when receiving a large number of faxes
>> > on a
>> > system using IAXmodems?
>>
>> File system contention, but fax files aren't very large, and I would
>> call that a non-issue. Most people don't want a piece of paper; they
>> want a PDF that they can turn into paper once in a while.
>>
>
> The purpose of such a system as I'm inquiring about is for digital
> archival. Very little 'paper' will be in use. Buffering aside, each
> fax could be written at the speed at which it is received correct? So,
> if I'm receiving 50 faxes at 14.4kbps each, assuming a direct receive
> frame-->block write, I'd be looking at roughly 90KBps written to disk.
> Is my logic sound here?
>
> Thank you for the response and ideas.
>
> Marshall
>
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