[asterisk-dev] Virtual Modem Pool

[Steven S. Critchfield]

Seems like a very stupid way of doing this. Modems do not do well over
VoIP connections. Even if you could get a connection to be made and
stay up for long, any jitter in the VoIP connection will kill your
throughput. You will still be sending the same amount of data per
VoIP call and getting much less end to end bandwidth.

You would be SOOO much better off if you just looked at contracting 
with some service like TiVo did to provide POP access and do modem to
PSTN to POP, then you have internet access for your download. 

Just for the quick math.

uncompressed VoIP ~ 80kbps bandwidth from you to your VoIP gateway
2400bps signal that might be usable over voip.

hmm, you loose 76kbps of data trying to support that idea per line in
use.

----- "Brad Silen" <brads at qualityprocess.com> wrote:

> We are looking to deploy thousands of hardware devices connected to
> the PSTN
> which will upload data and download firmware updates using v.90
> modems. It
> will be deployed to a demographic which does not have Internet
> access.
> 
> We are hoping to avoid setting up an old fashion modem pool, POTs or
> T1-PRI,
> and hope to access the PSTN through a SIP Trunk or IAX2.  This
> solution
> would be both cost effective and scale to handle peak loads; For
> example,
> when a firmware download is required.
> 
> Ideally we would like our application servers to send/receive using
> TCP/IP
> sockets with the virtual modems which are being driven by the VOIP
> infrastructure.
> 
> The network might look like:
> 
> Device <--> POTs <--> VOIP Gateway <--> IAX2 <--> ??? <--> Clear Text
> on
> TCP/IP Socket
> 
> Solve for ???
> 
> Has anyone used Asterisk in this way?
> 
> Is there any reason why the VOIP Gateway (SIP Trunk or IAX2) data path
> would
> prevent modem communication?
> 
> Is there any similar solution terminating a v.34 connection (aka Fax)?
>  A
> Fax solution would verify the ability to send data via the VOIP
> pathway and
> offer sample code as a starting point.
> 
> Would we extend the Asterisk concept of an "extension"?  For example,
> instead of forwarding the traffic to a SIP Phone the virtual modem
> would be
> an "extension" which converts the data stream to ASCII clear text. 
> Or, what
> would be the suggested architecture choice in Asterisk?
> 
> Note, I am very open to better, easier, or more clever solutions.
> 
> If there are service providers offering this type of virtual modem
> pool
> please have your shameless commerce division email me directly.  I
> suggest
> they not respond to the list since I am concerned it would violate the
> rules
> of this list.  I have not been able to find a solution and expect to
> contribute.
> 
> 
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-- 
Steven Critchfield critch at basesys.com