Gopinath (9711107) enscribed thusly:
> Hi everybody,
> 1 I wanted to know if the commands that are sent via the
> ftp control connection may be split across more than
> one TCP segment or will always go in a single TCP
> segment. And why so?
> (For example, if the client issues a command like
> PORT or PUT, is it possible that first few characters
> go in a segment and the next in a different segment and so on..)
Define "a segment"? Do you mean an IP datagram or fragment? If so
then the answer is... Of course. That's not even necessarily under control
of the application.
TCP/IP is basically a stream of data with a few "Out Of Band"
signalling conventions. Lots of the protocols such as smtp, ftp, http,
etc, etc, use a line oriented protocol. They send ascii commands which
are delimited by new lines, generally a CR/NL termination. A command
may be split across several IP datagrams at the discretion of the low
level protocol stacks (subject to the absence of the "do not fragment"
option). The server at the other end merely reads lines. It does not
know or care if that line came across on one, two, or more datagrams.
> 2 A related question is whether it is possible to look at a
> ftp packet at the network level and and say for sure the
> offset at which the ftp commands will be present.
In general, No. Typically, you may catch most of them.
> TIA
> gopi
Mike
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