>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.
Unfortunately, I don't know of an online link. The Cisco University
voice courseware lacked it, and I tended to do this material at the
whiteboard. I go into it to a reasonable extent in my new book, WAN
Survival Handbook (Wiley).
>
>
>
>
>-----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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