[Asterisk-Users] ISP connection to the PSTN using Asterisk

[Ronan Mullally]

Hi Ashling,

On Mon, 24 Jan 2005, Ashling O'Driscoll wrote:

> Could someone let me know the most common way that an Internet ISP
> would allow customers access to the PSTN?? Do they buy multiple fxo
> cards such as the TDM400P and rent multiple lines from a larger
> provider??

Do you mean how does an ISP allow its customers to make outbound voice
calls using its infrastructure?

Most ISPs these days will use something like a cisco AS5300 or AS5800, or 
an Ascend MAX TNT (it's been 5 years since I've played the ISP game, these 
model numbers are probably dating me ;-).  They take multiple PRIs from 
the telco(s) which can be terminated as either individual B channels (for 
ISDN calls) or into "digital modems" (for analogue modem dialup).  AFAIK 
the latter can be used as DSPs to permit in/outbound voice traffic.

> Would the best way be to connect to a third party voice/pstn
> gateway?? Is that simply a matter of forwarding all sip traffic
> destined for the pstn to another provider with a gateway and then
> they have to worry about the number of lines etc??And if that is the
> case, I presume no extra hardware is required?

Depending on the economics involved this might be a sensible way of doing 
it - a third party could be enlisted to take the SIP traffic and deliver 
it to it's ultimate destination.  The hand off would most likely be across
a private interconnect (ethernet within a co-lo, or a dedicated circuit 
between sites) to ensure the link is not congested.


-Ronan