Re: PM3 E1 to E1 direct connection

Kyle Platts (kwplat1@reliant.uswc.uswest.com)
Fri, 29 Aug 97 16:25:41 -0500

>You are absolutely correct. We proved it when we had us west out =
here and
had one line span plugged in and had a T-bird plugged into the =
other and
saw a clock. The clock does "bleed over" that is why you have a =
problem

The clock does not bleed over, and Livingston is correct in saying =
it does not provide clock. What happens is that line 1 uses line =
0's receive clock as it's transmit clock. The 2 clockrates in T1 =
must be identical in order to function correctly.

>when using 2 different CO's for each span. We were trying to see =
if the
pm3 was in fact providing a clock. The problem is you do see some =
timing
slips.

Actually, you should not see a difference between 2 lines coming =
from 2 different central offices, UNLESS the 2 offices do NOT =
reference the same master clock. In most CO's, they use a master =
distributed clock, so the clock in one office is the same as =
another. Of course, this isn't always the case (due to a number of =
different factors), but in a metropolitan area, the =
switches/dacs's/d4 banks take timing off of the tandem switch.

When you run frame relay on one interface, and a CT1 or PRI on the =
other, the PRI and CT1's transmit clocks come from the BITS clock =
in the office. In frame relay, the switch provides the transmit =
clock source.=20

I would verify your frame relay link is not taking slips. The =
frame relay provider's switch should be set to loop if the switch =
does not use an office clock for it's transmit clock source.

Kyle Platts
CSS-Tech
!NTERPRISE Networking Services=