E1 PRI splitter for Call Manager Express

[pratapag5]

Hi team,

I have a query regarding E1 PRI splitter. We are setting up a new office with 2 CME routers (will be in redundant mode) and 1 E1 PRI terminated  on the primary router. We want to be able to use the PRI in case the primary CME goes down. We are actually looking into purchasing another E1 PRI which will be terminated on the second CME router, but it looks like using a splitter with single PRI is a cheaper option.

Could you please let me know the feasibility and pros/cons of using a splitter here when compared to purchasing a second PRI? I have read that

E1 circuits cannot be split like analog ports and that we need to use a Y cable (but we must always keep one interface shutdown). Please let me know how to use a splitter/Y cable here and where it can be purchased (vendor and cost information).

Also, I am not sure if there will be any voice quality issues with splitter/Y cable.

Thanks in advance.

Regards,

Suchitra

[paolo bevilacqua]

First of all, when using cisco router, you don't need to worry too much about redundancy. Their failure rate ix extremely small, much smaller than circuit failure rate.

Second. There is no real splitter/Y Cable for E1 circuits,because is not possible to make one due to the electrical considerations. You can make a manually operated A/B switch, but is probably not even wort it. If you have to move the circuit from one router to another, just move the cable, and that's it.

Anyway, this kind of considerations come most often from people that never had a Cisco or CME before. My recommendation, make the system work perfectly first, worry about redundancy after.

[pratapag5]

Thanks a lot for the reply, Paolo. We considered manually moving the circuit from one router to the other (when primary router fails), but we thought that is not an elegant design solution for a Trading office. Also, we might not have a Systems person readily available in that office to move the circuit. We want to have redundancy in case of primary CME failure.

>>You can make a manually operated A/B switch,

Could you please let me know what this is exactly and what does it take to make one.

Can we make use of  a Y cable/BNC connector here (I am not exactly sure how it works but I have read that we can make use of a Y cable as E1 PRI splitter). If this (splitter/Y cable or A/B switch) is not recommanded, we are inclined towards purchasing another PRI with same DID range and pilot number.

Regards,

Suchitra

[paolo bevilacqua]

An A/B switch only changes one circuit between two users.

Again: make it works first, that will keep you busy enough.

[pratapag5]

What about the Y cable?

Regards,

Suchitra

[Brandon Svec]

I agree with Paolo about this in general, but I have also heard of mechanisms to accomplish what you want.  Here is an example:  http://dataprobe.com/t1_protection_switch/index.php

However, you need consider carefully what type of failure you are trying to provide redundany for.  As an example if you have a unit that senses a T1 outage on the CPE1 side and automatically moves the PSTN circuit to the CPE2 you are only protecting against VWIC failure or maybe power failure.  What if the router locks up or crashes, but the T1/E1 still appears up?

[paolo bevilacqua]

That is the point I'm trying to make. I never seen a failed interface card, and if the router crashes, it restarts.

[david.trachsel]

Hi. The way I would accomplish this is to purchase an Adtran Atlas 550 with three E1 interfaces. You can have the E1 from your vendor coming into one interface and from there you can create a routing plan on the Atlas to divert different channels to each of the other two interfaces. This will also allow you to divert all channels from a failed interface to a working interface.

Good luck

Dave

[paolo bevilacqua]

And what happens if the "active splitter" device fails? I don't think they can demonstrate a better MTBF, or shorter RMA turn-around time than a Cisco router.

[david.trachsel]

Obviously, the best solution is to have a second E1. 

Best

Dave

[Dennis Mink]

If redundancy is that important,  then order 2 PRI's and terminate one on each CME router.

From the Telco's point of view you will need to have the same DID range routed to two PRI, I am not sure what country you are in but here in Australia that means load balancing in round robin fashion, until one of the PRI goes down.

You will need to do some tricks with your dial peers because with load balancing, calls will land on the CME router that has no phones register to it, so you will need to point your secondary router to your primary etc etc.  Its possible and you will need to test it against all types of failures (PRI outage, router down etc.)

Good luck

[pratapag5]

Hi team,

Thanks a lot for for all the information.

I am currently going through the two products mentioned in the above replies: 1) Adtran Atlas 550 and 2) Automatic protection switch, which can be used to make single PRI avaliable in case of the CME failure. But, I am not very sure if using one of these is the correct way to go.

>>Obviously, the best solution is to have a second E1

David, could you please let me know why you think a second E1 is better than single E1 with atlas 550 or protection switch?

Regards,

Suchitra

[pratapag5]

Thanks a lot for all the details, team.

After discussing all your inputs, we have finally decided to take a second E1 PRI and terminate it on cme2.mjv.

Once again, thanks for the details.

Regards,

Suchitra