[MUD-Dev] UDP vs TCP/IP

[Ola Fosheim Grøstad <olag@ifi.uio.no>]

Daniel.Harman at barclayscapital.com wrote:

> Admittedly I'm not much of a Windows guru, but from the little bit
> of poking I did with netstat (-a shows all connections and -s
> shows per protocol statistics) it seems to me that AO only makes
> use of TCP (and not UDP or something else above IP).

Quite possible, but I looked at this several months ago and noticed
that there was a couple of TCP and UDP.  I'd be curious if someone
could check this out? It would make sense to skip UDP in times of
congestion, so it might be a good idea to test this in "good
weather".

> is my belief (as well as that of other game coders, researchers
> and academics) that TCP is not well suited to real-time
> applications (real-time refers to the fact that obtaining a
> "timely" solution (or delivering a message in a "timely" fashion)
> is as important as actually producing the solution or delivering
> the message).

IP4 and anything on top if it (with some special case exceptions
designed for multi-media streaming) is totally unsuitable for
real-time, but real-time is not necessary for games.  Real-time
generally means that there are hard guarantees.

> thing is that we get *everything* that was sent. On the other
> hand, consider a phone call: we tolerate losses (think of the poor
> quality of cell phone calls) because the most important thing is
> that we keep up with the conversation - getting everything is just
> not that important.

I don't get this?  A rather inappropriate analogy.  Phone calls are
real-time, with fixed bandwidth.  Audio is the most sensitive medium
you can deal with.  QoS has an incredibly high priority with
telecoms.  So high in fact that it has taken far too long for them
to provide packet-switched services.

> This brings me back to the lag meter and how inaccurate it
> seems. Sometimes it will be green but I will be unable to interact
> with the world (I will try to sit, but 30 seconds later I am still
> standing). At other times it will be red but I can interact with
> the world just fine (I push 'x' and my character sits right away).

This is all pure guesswork.  Could be a choking server and bad
measurement (i.e. only looking at time-stamps, which is useless if
you don't get any).

> Anyways, I spent a good amount of time typing this up, and would
> appreciate any comments or criticisms.

I'm not convinced that dumping speculations off message boards is
the best idea. Anyone could come up with hypothetical stuff like
this. There are more interesting information out there though.  The
developers seem to like open source toolkits.  I've found hints of
Qt, APE and more on the web.

--
Ola  -  http://www.notam.uio.no/~olagr/

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