Re: AS/400 IP COMMUNICATION WAIT TIME

Jim,

I think we agree.  Just saying it a little bit differently.

Bob

----- Original Message -----
From: Jim Langston <jlangston@conexfreight.com>
To: <MIDRANGE-L@midrange.com>
Sent: Friday, January 07, 2000 2:01 PM
Subject: Re: AS/400 IP COMMUNICATION WAIT TIME


> Bob,
>
> Actually, HTTP does use connection based, but in short
> spurts.  The way HTTP works is the client requests a
> file from the server, the client connects and establishes
> a connection, then the client requests the file, the server
> sends the file and closes the connection.  Every graphic
> you see on a web page was actually downloaded using
> a separate connection.  TCP is connection based, it's
> just that HTTP is not.  Although it uses TCP to get the
> files.  If you were receiving a web page file from a
> HTTP sever and disconnected your ether net and plugged
> it back in in the middle of the transfer, you would not
> receive the rest of the file.  Unless you hit "refresh" and
> then it would download the whole thing again.
>
> UDP is used for broadcasting because it is not permanent
> connection based.
>
> Regards,
>
> Jim Langston
>
> Bob Crothers wrote:
>
> > Jim,
> >
> > You've got it mostly right.  Except the part about TCP being
"Connection
> > Based".  It does not have to be that way.  Look at HTTP.  The
connection is
> > not maintained for the duration of the session.  Only while data is
being
> > exchanged.  Other protocols/applications are different.  Telnet is
> > connection based.  FTP is actually both.  The control part of the
> > conversation is connection based, but data is exchanged over a
> > connectionless conversation.  And custom applications can be how
ever you
> > want them.
> >
> > The main difference between TCP & UDP is that when you send data
via TCP, it
> > is guaranteed to not only arrive at the destination (or cause an
error) but
> > also in the same order you send it.
> >
> > When you send with UDP, not only is the data NOT guaranteed to
arrive at the
> > destination, but the data MIGHT be out of order.  As a result, UDP
tends to
> > be used for "trivial" things (like ping) or broadcast where each
byte of
> > data is not that important (streaming sound/video).
> >
> > Bob
>
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