SIP Trunking Mantra (Origination)

Home » Asterisk Users » SIP Trunking Mantra (Origination)
Asterisk Users 4 Comments

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!


4 thoughts on - SIP Trunking Mantra (Origination)

  • Hello Jai the benefits of SIP trunking is well noted. However, there will always be an underline interconnect that makes SIP trunking possible. What I am trying to say is that there will always be ISUP/ISDN trunk groups that we throw a TCP/IP stack on top, and offer clients with SIP trunking. We are looking for information on how to accomplish interconnect using ISUP trunks (i.e., SS7 interconnect).

    Kind Regards,