The agreement for a 53 byte cell is the worst mistake made by politicians,
it should be a 2^X for acceptable optimized and efficient transportation
Either 32 or 64 was acceptable
This is a classic example of politicians intervening in standards committee.
Prasad
""Rahul Kachalia"" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Hi All,
>
> There were several different reasons for choosing such smaller size of
> payload carrier some of them as follows :
>
> Why such a small-sized packet for ATM? Why not larger than 48 bytes in the
> payload (48 bytes is very, very small)? The answer to that is simple. ATM
> and the inventors of ATM targeted the single challenge-to reduce delay in
> the network. If we have large packets they take a long time to
assemble.For
> instance, we know that a DS0, Plain Old Telephony service is running at
> 64,000 bits per second. If you take that 64,000 bits per second and divide
> it by 8000, which is an 1/8000 of a second, you end up with 8 bits every
> 1/8000 of a second.
> That's very repeatable; its going to be the same in any country. If we
> know we're getting 8 bits, or 1 byte every 1/8000 of a second, we know
that
> filling up a packet is going to take a measurable amount of time (1 byte
> every 125 microseconds). If we make the packet long, it's going to take a
> long time to fill it up. This is called cell assembly delay. In order to
> maintain delay constraints that were targeted towards ATM, they decided to
> make these packets very, very small. It would have been better for file
> transfer for data application to have a longer packet, but they erred on
the
> side of voice-to maintain a Quality of Service for voice in a packet
> network, similar to today's TDM networks. That's why it was so small. It's
> all about that cell assembly delay.
> Voice and video applications are sensitive to delay, especially when it's
> interactive. When you're talking to someone on the phone, and they're
> talking back at you, this is where delay becomes very important. We have a
> test that we often do for this kind of thing: if I were to say "one," and
> then you were to say "two," and I were to say "three," and we were to go
> back and forth as quickly as possible, we would be able to understand
> exactly how much delay exists in this interactive conversation. It's a
great
> test for delay.
> For non-interactive, for instance, when I'm just speaking to you, and
> there's no real interaction with me, delay isn't as important. Perhaps we
> could have gotten away with longer packets for this type of application.
ATM
> elected to default to the best performance for interactive voice.
>
> hope this helps everyone...
>
> regards
> rahul.
>
>
>
>
> --------------------------------------------------------------------------
--
> ----
> © 1984-2000 TRA. All Rights Reserved.
> ----- Original Message -----
> From: "Circusnuts" <[EMAIL PROTECTED]>
> To: "themitmo" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> Sent: Saturday, October 21, 2000 4:29 AM
> Subject: Re: Why 53-bytes for a cell & AL GORE
>
>
> > Al Gore thought up the 53-byte cell after he invented the Internet :-)
> >
> > Honestly- the best ATM books I've read (that were readable & not a bunch
> of
> > algorithms) were Global Knowledge's beginner series. They explain
> > international agreements between cell sizes, echo, QOS, etc., etc.,.
The
> > best ATM working explanation I've ever read, is Chapter 7 in the CCNA
WAN
> > Quick Start book (& I usually don't like Cisco Press :-)
> >
> > Good Luck !!!
> > Phil
> >
> > ----- Original Message -----
> > From: "themitmo" <[EMAIL PROTECTED]>
> > To: "Andy Xing" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> > Sent: Friday, October 20, 2000 8:08 AM
> > Subject: Re: Why 53-bytes for a cell?
> >
> >
> > > Because back when they were creating an ATM standard
> > > from stratch it had to be some number. I believe there
> > > were two factions (US vs. European) on what size the
> > > payload area should be. 48 bytes turned out to be the
> > > compromise between speed and size.
> > >
> > > --- Andy Xing <[EMAIL PROTECTED]> wrote:
> > > > Thanks
> > > >
> > > >
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