[asterisk-users] SIP Trunking Mantra (Origination)

[Nick Khamis]

Hello Everyone,

We are currently having talks with various service providers, and
trying to determine what the best way is to interconnect in order to
have access to the PSTN network. As you know there are two ways of
doing this:

Traditional PRI: Have trunks grouped into a transport layer such as
OC3/12. With DIDs attached to the group. As you many know, this
approach would also require a POP near the CO of the exchange we want
to service etc.. We could also have the service provider backhaul some
of the NXX in areas we do not have a POP, to a location near by.

SIP Trunking: SIP traffic coming through the end of transport layer
such as OC3 or ethernet connection directly connected to the service
provider, with DID that can come from anywhere. No need for a POP in
Chicago, for example, when we are located in Kansas.

The benefits of one over the other are known, and not the topic of
this message. What we are trying to determine are:

When talking market price, a "virtual PRI/SIP Trunk" interconnect
costs about 500-550 per 24 channel virtual pri. This compared to a
true "ISDN/PRI" which can costs between "200-500" dollars depending
who you talk to. We also have to take into consideration the hardware
needed for either setup i.e.:

* Option 1: SIP Proxy
* Option 2: media gatweays, multiplexers, media server....

Even though it was natural to talk about "pricing", this is still not
what we are interested in knowing. What we are interested in finding
out is:

* How are service providers that offer "virtual pris" interconnected
with their suppliers? I would imagine that some (non-CLECS), are
renting a connection from the LECs, and grouping PRI/ISDN trunks
(option 2). And others (CLECS), have a A-Link/ISUP trunk interconnect
to the CO.
  - Which brings up a second question. How does a PRI trunk group
differ from an ISUP
    trunk. I don't know much about and ISUP trunks and would *really*
appreciate having
   someone educate us on (i) the concept, (ii) what type of equipment
would be needed,
   (iii) how it differs from ISDN trunk groups. (iv) is it only
available for LECS

I do have more questions, however for the sake of brevity will stop
right here. And before anyone asks the "it depends what you want to
do", I will mention that we are trying to establish an interconnection
that will sustain 2016 channels or 84 T1s, and 5000 DIDs. We are not
trying to become a CLEC however, still feel that option 2 would be the
better choice for reasons covered here, and some that are left
implicit (i.e, quality, reliability of managing our own
networks......).

Your insights are greatly appreciated!

Nick.