atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Fax problem caused by RX slips. (T1/Titan5500/5ESS)

Can you find out what the two failing T1s have in common. Anthony has a good suggestion. Find out if they ride on the same T3 and try switching the circuits to the protection card.

Bill’s right, ONE GOOD timing source can’t cause slips.

BUT… One BAD (or going bad) timing source can cause slips.

Also, TWO or more good timing source trying to control the timing of a circuit can cause slips.

Hopefully that’s already understood… I’m pretty much out of ideas on this one… :rolleyes: Well, good ideas anyway.

Let me clarify that just a bit Bryan. I was talking source as in Verizon, AT&T ect. As everything from the carrier would be bad. CPE timing sources can go bad as you pointed out.

Also, TWO or more good timing source trying to control the timing of a circuit can cause slips.

I am of the belief that this is what is causing this.

I just proactively found 3 more customers that are all taking slips on the t1 that serves voice. They are all multiple T1 customers.

They are all in different latas and ride over different DS3 facilities.

Again, the only common thing is that they are connected to the 5E for voice and our ciscos for data. The Cisco's are 7500s that are set to time off of the loop. The 5E is using a bits clock.

have you gone as far back as the oc3 (or 12 or 48, or whatever you are using)

Different circuits, riding different rings, may still ride the same oc3. I really do not think the problem will be in the 5e

I hear ya Anthony even though everything seems to point to the 5E because when it's not in the picture, neither are the slips. As many of you might imagine, I'm quite frustrated with all of this.

I am working with my supervisor today and seeing how we can escalate this to have the OC circuit facilities checked.

I wouldn't think it would be larger than the T-1 level or you'd be having a lot more problems, especially on data. If the only common thing is the 5E that's where I'd look. Anthony, when a 5E is used for a tandem switch it's slaved off the master clock isn't it? Don't know how you could have two 5E's in tandem with both suppling clock. I'm sure it would be at the T-1 level in the DTU (maybe not the right term for the T-1 cards)

Was this problem ever resolved? Lots of good help has been given!!

Not as of yet. We are still working on this. Sadly I don't see much progress.

Well boys and girls it is with great pride that I come to you today with great news!

Yesterday we were finally able to pinpoint some crucial differences and similarities that gave us a way to stop the slips.

1) All of the customers have at least 2 T1s or more.
2) All of the customers had at least 1 T1 configured for voice (went to a 5ESS) and 1 configured for data (went to a Cisco 7500).
3) All of the customers had a Carrier Access ADIT 600 router and both (or more) T1s went into it.
4) All of the Carrier Access ADIT 600s were set to time off of A:1 which is the first T1 slot.

Now here is where things were different...

Some of the customers had the voice going to T1 1 and the data going to T1 2. Some were the other way around.

Those that had voice on T1 1 and slot 1 was the timing source were fine on all ports.

Those that had data on T1 1 and slot 1 was the timing source took slips on the "voice" T1 which would be in a different slot.

Changing the clock source for the router to use the VOICE T1 (regardless of slot) stopped the slips from occurring.

Now the big question is, why would this be an issue? We time off of the loop for either voice or data. The real difference is that the 5E has a BITS clock and is set to be a master and the Cisco 7500s are set to recovered/loop timing.

Thanks for everyone's help with all of this. I'm glad that I can post a solution to the problem. (Even though I still would like to know the difference of timing on the voice T1 instead of the Data T1)

Fred