Guy,
it would yield 726 only if you were using an
Ethernet SNAP frame.
For Ethernet 802.3 (6 byte destination + 6 byte source
(mac addresses) + 2 byte length field + 1 byte SSAP +
1 byte DSAP + 1 byte control + 700 payload + 4 byte
CRC) = 721.
For Ethernet Raw (6 byte destination + 6 byte source
(mac addresses) + 2 ethertype + 700 payload + 4 byte
CRC) = 718.
For Ethernet SNAP (6 byte destination + 6 byte source
(mac addresses) + 2 byte length field + 1 byte SSAP +
1 byte DSAP (both = 0xAA) + 1 byte control + 5 byte
OUI + 700 payload + 4 byte CRC) = 726.
Regards,
Phil.
PS: I think there is a pocket handbook by Miller that
explains this in more detail.
--- "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, must be at least 64 bytes,
> and is not padded
> further. So that if the packet is 700 bytes, and is
> encapsulated in an
> Ethernet frame, the total would be approximately 726
> bytes. 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
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