[lug] [OT] WIC T1 or 56k

[TJ Schuler]

This is correct. A DS0 by definition in the US is a 64K channel - the
difference between 56K and 64K is how the equipment handles the actual zeros
and ones on the line. DS-1 lines require no more that 15 "0" bits before a
"1" bit being sent. This is a requirement to keep timing on the line
correct.

Anyways one of the ways to do this is to make every 8th bit a "1" and only
use the first 7 bits for the data. This is how we get 56K service with DDS.

The other way to do this is to use a mechanism like B8ZS, which replaces
blocks of 8 zeros with the B8ZS code value. So you have a 64k timeslot but a
certain amount is overhead, some say it is 56K usable - but it really
varies.

I like to use the example of videoconferencing of the WAN. In the old days
with H.320 we used to channalize a T1 and use certain timeslots for data and
certain for video.  Now this worked fine and looked alright the problem was
that you couldn't ever use the "video" timeslots for data if they were not
being utilized. This is similar to the 7/8 method used in DDS. Now with
H.323 and Video over IP we can dynamically allocate the bandwidth to the
video over the data timeslots and reclaim that bandwidth when not in
use -works just as good if not better and a lot more flexible.

--TJ

TJ Schuler, CCIE #8800
Coleman Technologies, Inc.
720-981-4276 Office Phone
720-339-6000 Cell Phone
http://www.ctiusa.com
----- Original Message -----
From: "Timothy C. Klein" <teece at silverklein.net>
To: <lug at lug.boulder.co.us>
Sent: Wednesday, September 25, 2002 8:54 PM
Subject: Re: [lug] [OT] WIC T1 or 56k


> * Sean Reifschneider (jafo at tummy.com) wrote:
> > On Wed, Sep 25, 2002 at 03:44:10PM -0600, TJ Schuler wrote:
> > >This really will depend on what type of 56K circuit you have; if it is
a DDS
> > >circuit like most 56k lines I have seen then it will not work, but if
it is
> >
> > My first thought on hearing "56k" was that it was a frame relay line...
> > Which affects the situation in weird and wonderful ways...
> >
> > Do they actually do "fractional T1"s that aren't a multiple of 64K?
> >
> > Sean
>
> The way they described it when I used to work in telecom was that all
> the DS0 circuits were 64K, but 56K was all that was usable, the
> remaining 8K being "overhead."
>
> Tim
> --
> ==============================================
> == Timothy Klein || teece at silverklein.net   ==
> == ---------------------------------------- ==
> == "Hello, World" 17 Errors, 31 Warnings... ==
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