[OT] Handling multiple UDP clients through NAT

Bryan Sant bryan.sant at gmail.com
Wed Feb 7 11:11:15 MST 2007


On 2/6/07, Erik R. Jensen <erikrj at netradius.com> wrote:
> Bryan Sant wrote:
>
> > UDP is built on IP (and TCP is built on UDP)
>
> TCP and UDP are both built on IP. TCP is not built on UDP.
> TCP and UDP are peer protocols.
>
> I apologize if it was just a typo, but wanted to clarify.


No typo, but it is wrong.  When you look at a chart of the TCP/IP
stack you'll probably see the UDP and TCP protocols side-by-side.
However, TCP is actually a super-set of the features of UDP.  In the
OSI network model, IP maps to layer 3 (network), UDP and TCP both map
to layer 4 (transport).  However, if you could split layer 4 in two,
there would be a lower portion that UDP handles and a higher portion
that TCP handles.

UDP sends datagrams.
TCP manages datagrams with reliable delivery (acks, time-outs,
resends, etc), packet ordering, flow control/windowing, etc.

I am incorrect in stating that TCP is literally built on top of UDP.
I doubt they share any code, or that the TCP code is an addition to
the UDP code, but the TCP feature set is a super-set of UDP.

-Bryan



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