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From: ed@mtxinu.UUCP (Ed Gould)
Newsgroups: net.lan,net.dcom
Subject: Re: UDP protocol
Message-ID: <28@mtxinu.UUCP>
Date: Thu, 22-May-86 13:26:27 EDT
Article-I.D.: mtxinu.28
Posted: Thu May 22 13:26:27 1986
Date-Received: Sun, 25-May-86 18:05:10 EDT
References: <1807@gitpyr.UUCP>
Reply-To: ed@mtxinu.UUCP (Ed Gould)
Organization: mt Xinu, Berkeley, CA
Lines: 29
Keywords: UDP, TCP, IP
Xref: watmath net.lan:1512 net.dcom:1942

>Can someone explain to me what the differences are between UDP and
>TCP ?  I understand that both are OSI level 4 protocols and both
>run over the IP protocol.

UDP (``User Datagram Protocol'') is an unreliable datagram protocol.
It is connectionless, meaning that there is little overhead sending
a datagram.  ``Unreliable'' means that the sender has no way to know,
other than by cooperation of the reciever, if the datagram was
received.

TCP (``Transmission Control Protocol'') is a two-way, connected,
byte-stream protocol.  The protocol ensures that data is delivered
exactly once and in the correct order. or an error indication is
returned to the sender.

Both are built on top of IP (``Internet Protocol'') which deals with
issues like packet fragmentation (if the packet sent by TCP or UDP
is larger than the lower-level transport mechanism will handle) and
reassembly, addressing, and internetwork routing.

More details of these, and countless other protocols, can be found in
the appropriate RFCs (``Requests for Comment''), whose numbers I
don't have handy.

-- 
Ed Gould                    mt Xinu, 2910 Seventh St., Berkeley, CA  94710  USA
{ucbvax,decvax}!mtxinu!ed   +1 415 644 0146

"A man of quality is not threatened by a woman of equality."