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Cell Relay Retreat>List Archive>month:1999-May> msg00005



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Re: CR: Re: Why atm use 53 byte?

  • From: "Gary Kessler" <g.kessler@hill.com>
  • Date: Mon, 03 May 1999 13:35:23 -0400
  • X-Sender: g.kessler@mail.hill.com

Hi all.

At 23:03 05/02/1999 PDT, Jerry Mendes wrote:
>Too bad no one from Bell Labs responded to this question.  My recollection
>dates from the late 80s, shortly after the ATM cell length had been agreed
>upon through international standards group -- I'm not sure whether it was
>through ISO or CCITT (predecessor of the current ITU-T).  U.S. proposals
>wanted 32 octet cell length, to optimize ATM performance for voice
>networks (hence, Bell Labs interest).  European proposals, driven by
>greater efficiency for data transmission, were written with 64 octet cell
>lengths.

I think that this is backwards. The U.S. and other countries employing T1 technology wanted 64 byte payloads which incurs an 8 ms delay to acquire all of the voice samples using PCM. The Europeans and other countries wanted 32B payloads (4 ms delay).

>In fact, the 48 octet length was an arbitrary compromise between the two
>as suggested by an earlier poster.  I'd suggest having a look at IEEE
>Communications or IEEE Network magazines from 1987 to 1989 time frame if
>you want to see the discussions.

I agree!

/kessler

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