3) Why is the ATM frame size 53 bytes?
I bet if we counted how many times this question was asked it would be near
100.
Well if telecom guys would've gotten their way and the size was set for
telecom to prevent delay and jitter it would've been smaller than 32 bytes.
What I have read is that it was a compromise between the data side (wanted
atleast 128 bytes)and the telecom side (wanted less than 32 bytes or it
would need echo suppressors) which I'm sure made everyone evenly upset.
>>>Brian
>From: "David L. Blair" <[EMAIL PROTECTED]>
>Reply-To: "David L. Blair" <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Subject: Re: why there is an ethernet frame size limitation
>Date: Wed, 24 Jan 2001 14:28:31 -0500
>
>I know the reason for two of three.
>
>1) Why is the Ethernet minimum frame size of 64 bytes?
>
>Ethernet timing is based upon "bit time" the time a bit takes to travel
>the
>distance of an maximum Ethernet segment length 100m or 328 ft. The
>minimum
>frame size 64 bytes equals 512 bits or 512 bit times to travel the wire.
>This has to do with a host on one end of the wire listening to use the wire
>and another host on the opposite end transmitting. Note: This does not
>include the Preamble.
>
>2) Why is the Ethernet maximum frame size of 1518 bytes(not 1526)?
>
>I guess for a similar reason. Remember most Ethernet implementations are
>share media. So everyone host is contending for access to the wire. That
>is why Ethernet is contention based and Token Ring & FDDI are
>deterministic.
>A packet to large would actually allow less hosts per segment to transmit
>their data in a timely fashion.
>
>3) Why is the ATM frame size 53 bytes?
>
>I do know exactly why 53 bytes was picked. I do know why a small frame
>size
>was picked. A ATM packet has two parts: Address and Payload. The Address
>is 5 bytes long and the Payload is 48 bytes longs. ATM was designed as a
>Multi-service access medium, i.e. to handle Data, Voice, and Multimedia
>content. The "Holy Grail" of voice transmission is delay and jitter. When
>the Delay in voice transmission is more than 250ms, humans start talking
>before the other person has finished. Resulting in a garbled conversion.
>It takes less time to fill small frames with data. All the frames are the
>same size so the transmission time, for a given network, is constant.
>QoS,
>Quality of Service, features are implemented in ATM to guarantee delivery
>of
>time sensitive frames like voice.
>
>
>I hoe this helps. A good Ethernet book with some ATM and FDDI information
>is Switched, Fast, and Gigabit Ethernet ISBN: 1-57870-073-6
>
>-dlb
>
>
>"azhar mumtaz" <[EMAIL PROTECTED]> wrote in message
>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Hello Guys:
> > What i want to know is why there is a limit that ethernet frame size
>cannot be
> > less than 64 bytes and more than 1526 bytes. I know that this is how
>ethernet
> > should be understand but whats the logic behind it. Similarly why we are
> > limiting cell size of ATM to 53 bytes.
> > Regards
> > Azhar Soomro
> >
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