Hello Everyone,

We are looking to setup an interconnection with a local ILEC. Basically we will be asking them for multiple DS3s muxed into a single STS-1/OC3 connection. We would then put our media gateway at the end of that connection. After demultiplexing, we would translate the signaling to SIP, throw an IP stack on top, and provide customers with a hosted SIP PRI solution.

My questions are:

* Is that typically how such interconnects are carried out? At a general level of course...
* Where does SS7 fit in this picture if anywhere
* Can tie trunks be used to connect the separate connections together. If so, do that mean we can share channels (i.e., DS0s) between the different POPs.
* Is this the best way to interconnect, and how does it differ compared to A-Links (ISUP Trunks)

What we are trying to accomplish is the following:

CO<------------>Our Network Core<---------> Internet (SIP PRIs)
ISDN over SONET

I have more questions, and can explain in more detail what we are trying to do however, will hold them back for the sake for brevity.

Kind Regards,

Mike.

I am just putting some links here that I will refer to at a later time (please ignore):

T1/E1/CCIS

Muxing DS3s

done

Move/merge ended up creating double posts... Removing duplication.

Anyone?

You take 3 electrical DS3's add the sonet overhead and you get a STS3. Then your mux converts the STS3 to an optical OC3 for transport on a OCN fiber. Is this your starting point?

Hello John, sorry for the delayed response, I was trying to educate myself a little more before responding. I have setup many T1 connections for customers with my father (I am 17), and was wondering what other options companies have to handle larger number of circuits in a cost effective manner.

From my understanding there are two main approaches to this (i.e., ISDN/PRI Trunks vs. SS7 Trunks). As for PRI trunks the basics are known (23B channels, 1D timing channel, out of band signaling..).

Sorry for the detour however, my question is where does SS7 fit in the PRI world. From the research I have done, I am able to understand that SS7 provides only signaling that carry info such as CallID, and LNP. What I can't understand is where does the call passing signal come from in an SS7 interconnect?

As a starting point I also understand that a point code (a kind of address) is needed to identify the SSP in an SS7 network.

There is a lot of material on the net when trying to understand PRI trunks however, not so much for SS7. I know there are a lot of sector professionals in this forum (have read your posts).. Hope I am not insulting anyone with this question :S.

Kind Regards,

Mike.

Good Moring PGM. In regards to your last response:
Most T1/DS1's sold are of the ISDN Primary Rate Interface type. They consist of 23 Bearer Channels at 64kb/s that can be used for EITHER voice or data. The 24th channel is labeled the Delta Signaling Channel also at 64kb/s. Most of the time the Delta's only purpose is to process call functions from the CPE EPBX Voice Bearer channels to the Signaling System Seven world wide network "gateway" at the LEC.

Kinda sorta example: Early in the last century and before dial telephones if I wanted to place a call from Denver to Milwaukee I would pick up the receiver which would signal the local operator that I was off hook. Once the operator in Denver new the number and where it was located she had to make a connection to say to the Omaha operator who would in turn make a connection to the Chicago operator who would make a connection to the Milwaukee operator who would see if the called party was idle. Remember this was one long Physical connection. It took a lot of people from Denver to Milwaukee to built it. What happened if the line was busy? All the Physical connections had to be manually taken down across the path from Denver to Milwaukee. Imagine the waste of technicians and operators time as well as interstate trunking resources.

PGM. Fast forward to the world of SS7.
A PRI Bearer channel wants to make a call from Denver to Milwaukee. The caller lifts the handset signaling an off hook. The Delta channel receives instructions from the EPBX that an off hook has occurred and get ready to process instructions to the SS7 Network. The Delta channel connected through software, will communicate with the SS7 Network. The SS7 Network will check its nationwide database to find the closest Central Office to the called party in Milwaukee. At the same time it will request that all switches in the path from Denver to Milwaukee reserve enough bandwidth for the call. Through its SS7 trunks to the called central office it will check with the switch to see if the called party is idle. If idle and only after a voice path has been reserved end to end will a voice path be cut through from Denver to Milwaukee and the local switch at Milwaukee applies ringing voltage. What happens if the number is busy? The SS7 network connection at Milwaukee signals the switch at Denver through the SS7 Network to either tell the local Denver switch or the EPBX to apply a busy tone to the Denver caller.

Hello John, Thank you so much for your response


Even though not as common, I would like to learn more about SS7 interconnects, and how they are generally performed by the carriers (i.e., point codes, signaling etc..). Basically how ISDN/PRI trunks differ from traditional SS7 trunks.

I hope this is not a stupid question .

Dear PGM,
First off "The only stupid question is the one that is NOT asked". Secondly, I applaud your thirst for knowledge, however this forum does not allow the space needed to go into a detailed overview of ISDN or SS7. May I suggest you first get the book "Understanding Data Communications" by William Held. It will provide a good base of Telecommunications and Data Communications including ISDN and SS7. After that I would suggest searching for a book on "Understanding the Basics of SS7 and ISDN" in non technical terms.

PGM:
If you would send me a PM with your mailing address I would gladly send you a book titled " Telecom Crash Course" at no charge.

Thanks,

John O

Hello John,

Thanks again so much for your direction. I have found the third edition of the the Wiley book online, as well as a copy of the crash course book. Will go through them and better educate myself on the parts I am unfamiliar with. Stay tuned...

PGM, An important part of understanding ISDN (and PRI's) is an understanding of the various interfaces and protocols as defined by the International Telephone Union's standard setting committees. Don't overlook them.