T-1 over ATM CBR

[brewerdude]

We're having some timing issues with tie lines we have running over an ATM CBR. We're getting massive amounts of frame slips during the day (users hear clicking on the line when they occur). AT&T has been making many adjustments to the ATM equipment (Cisco 8510), but haven't been successful. We've replaced the T-1 card and all cabling on our end, but nothing seems to help. Anyone seen this type of problem and have any ideas??

We have 81C's on both ends running 25.40. The ATM gear on both sides are Cisco 8510 catalyst switches.

 

[senk1s]

frame slips are just that ...slipping in clocks tracking.
in any network make sure only one clock exists and all other switches derive/extract clock from that source.
the ATM (or any other form of trasnsport) is not of any concern

 

[sossur]

We have 7 8510s in a ring. When using Qwest T1 clock as a network clock source 1, we have framing errors. NCDP did not help, system clock stopped the ATM framing errors, but we still have numerous CES/CBR timing errors. This is an on going problem, that has never worked properly. We have an active TAC going for this problem.

 

[brewerdude]

When we resolved this issue (it was ages ago) it turned out that we didn't have enough bandwidth for overhead on the CBR's. So we added about a meg, and haven't had a problem since then.