Re: [colorforth] bulk transfer protocol

[Mark Slicker <maslicke@xxxxxxxxxxx>]

On Wed, 5 May 2004, Samuel A. Falvo II wrote:

> On Wednesday 05 May 2004 11:52 am, howerd.oakford@xxxxxxxxxxxx wrote:
> > TCP is general purpose, but in practice uses packets consisting of 512
> > bytes of payload plus 20 bytes of header info.
> > The 512 bytes matches one disk sector on many ( older ) OS's.
>
> I'm unfamiliar with this "common" usage.  When I was working for the ISPs
> I managed, our MTUs were regularly set to 1500 octets, which seemed to
> work well, EXCEPT for our dial-up modem users, which used 576.

I've seen the 576 number called the "default" maximum packet size, I don't
know the origin of this.

I'm curious, where did the 1500 come from, was that a server option?

I was looking at some TCP packet dumps recently. Linux will use a
TCP option called MSS (maximum segment size) in the initial SYN
message, on my computer the value is 1460. With a 40 byte header (no
options) this amounts to 1500 bytes. So it apears the segment size can be
sugested by the reciever depending on the link type.

Mark

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