High-level view:
Remember there are multiple levels in the "T1" world. I'm
carefully avoiding "layer" If anyone starts trying to force this
into OSI layering, I will start to mutter, "This is a .44 magnum, the
most powerful handgun in the world. I can't remember if I've fired 5
or 6 rounds. Feeling lucky, punk?" :-)
The lowest level is the electrical/optical signal format
Next, you have bit stream encoding (AMI, B8ZS, etc.)
Next, you have framing (SF, ESF)
And with voice services, you have call control (CCS, CAS, etc.)
>
>Bruce Williams
>[EMAIL PROTECTED] wrote,
>On a T1 line what is the difference between 56K and 64K. If I am correct I
>believe that 56K uses bit stuffing to stuff the 8th bit of every timeslot
>with a 1 to fulfill the ones density requirement. However, this would not be
>necessary with B8ZS line coding, right because B8ZS will not allow 8
>consecutive zeroes anyway.
You're right about B8ZS, but 56K (and, for that matter, 48K) was
introduced at a time when AMI was extremely common.
>Now if that is true, why would you use 56K on a
>B8ZS coded T1 circuit and if those timeslots are cross-connected to a 64K
>line or vice versa, wont that cause errors because the two clock rates are
>expecting different things in the 8th bit. I would appreciate any comments
>at all on this subject.
But the DS0 sees a 64 KBPS stream and doesn't inherently expect any
meaning in any particular bit.
Bit meaning does come up at a higher level when used for telco
signaling, as with CAS and CCS.
------------
I didn't even _think_ of the acronym CCIE while writing the body of
this message. No ciscos were scaled, finned, or fried in its
preparation.
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
