[time-nuts] French Time offset

Lux, James P james.p.lux at jpl.nasa.gov
Wed Mar 18 18:21:03 UTC 2009

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Michael Sokolov
> Sent: Wednesday, March 18, 2009 10:56 AM
> To: time-nuts at febo.com
> Subject: Re: [time-nuts] French Time offset
> "Lux, James P" <james.p.lux at jpl.nasa.gov> wrote:
> > Things get done for funny reasons: After all, the physical size of 
> > France is why ATM "cells" (packets) are 53 bytes (48 byte payload) 
> > instead of either 32 byte or 64 byte payloads.
> Huh?  Can you please elaborate?  I thought the 48 octets of 
> payload were a compromise between the camp that wanted 32 and 
> the camp that wanted 64.
> MS,
> who has implemented the whole ATM/AAL5 stack in software 
> (looking at cell headers and all) for SDSL.

53 bytes was the longest you could do and not require echo suppression for a path across France.  The US is so huge, they had already bit the bullet on needing echo suppression, so they wanted longer packets, to reduce the header overhead (as a percentage).  There were also some "timing jitter" requirements, and how much buffering was considered reasonable for "real time" response in voice applications.

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