Here is a link to a White Paper on T-1 basics. It covers with moderate
detail what you are wanting.
http://www.ttc.com/downloads/white_papers/t1_tn.pdf
There are many other White Papers on the page I found the this one on that
might be of interest
to everyone.
http://www.ttc.com/technical_resources/white_papers/index.html
-Scott Brenner
CCNP/CCDP
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Christopher Larson
Sent: Thursday, December 21, 2000 5:47 AM
To: 'Howard C. Berkowitz'; [EMAIL PROTECTED]
Subject: RE: 56K vs 64K
Could you post a link or somewhere to get this info. I have been looking
and cannot find anything. I remember covering this in BCRAN and would
like to go through it again. Having to do with the serial lines and the
sampling rate, bit robbing etc. SF/ESF AMI/B8ZS etc. If you have a link
to this info I would love to read it over again.
-----Original Message-----
From: Howard C. Berkowitz [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, December 20, 2000 1:02 PM
To: [EMAIL PROTECTED]
Subject: Re: 56K vs 64K
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.
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