At 09:20 AM 7/19/01, Lupi, Guy wrote:
>Thank you to all who replied to this post. I do have another question for
>you. When the packet is sent to layer 2 for encapsulation and transmission,
>if it is Ethernet, an Ethernet header is placed on and the frame is
>transmitted. As far as I know the only requirement is that the frame must
>end on a 32 bit boundary
I don't believe there is any such requirement. TCP and IP headers must end
on a 32-bit boundary, but the data doesn't have to.
>, must be at least 64 bytes, and is not padded
The Ethernet driver may do the padding if the upper layer does not.
>further. So that if the packet is 700 bytes, and is encapsulated in an
>Ethernet frame, the total would be approximately 726 bytes.
That sounds right for most cases. To the 700, you would add:
8 bytes of preamble (This is usually not counted as part of the frame. The
preamble is used for clock synchronization.)
14 bytes Ethernet header: dest, src, type or length
4 bytes CRC
Maybe an 3 or 4-byte LLC header
Maybe a 5-byte SNAP header
> Is this
>correct?
>
>-----Original Message-----
>From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]]
>Sent: Wednesday, July 18, 2001 2:52 PM
>To: [EMAIL PROTECTED]
>Subject: Re: Packet Sizes [7:12826]
>
>
>FTP generally uses a full-size packet: 1500 bytes on Ethernet, not counting
>the header, CRC, preamble, inter-frame gap, or any VLAN or MPLS tagging.
>
>HTTP does not use a full-size packet usually. You would think it would, but
>it tends to use a 500-600 byte packet size. Using a shorter packet size
>improves perceived performance because the screen can show partial data
>while more data is en route.
>
>ICMP depends on what you are doing and what parameters you use. Most error
>or warning messages would be very short, probably 64 bytes or so. If it's
>ICMP echo (ping), then the user can specify the number of bytes.
>
>TFTP sends data in 512 byte blocks. Add the 8-byte UDP and 20-byte IP
>header.
>
>For all of these examples, there may be additional shorter packets for ACKs
>and other overhead.
>
>Priscilla
>
>At 11:41 AM 7/18/01, Lupi, Guy wrote:
> >Does anyone have a list of average packet sizes for different services?
> >Things like FTP, HTTP, ICMP, TFTP and the like. Just something general is
> >fine, I am aware that there is no hard and fast rule.
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
________________________
Priscilla Oppenheimer
http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=12986&t=12826
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