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<H1>[Nel] TCP vs. UDP</H1>
<B>Vincent Archer</B>
<A HREF="mailto:archer%40frmug.org"
TITLE="[Nel] TCP vs. UDP">archer@frmug.org</A><BR>
<I>Thu, 5 Jul 2001 18:04:42 +0200</I>
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<PRE>According to Vianney Lecroart:
><i> On Anarchy Online game, they only use TCP protocol between client and server
</I>><i> (other commercial online game use UDP) and it seems that it causes lot of
</I>><i> problem like horrible ping or connection lost:
</I>><i> <A HREF="http://aoforums.funcom.com/showthread.php?threadid=26297">http://aoforums.funcom.com/showthread.php?threadid=26297</A>
</I>
This post (and the rest of the discussion) do highlight the problems of
AO. However, only one post, in the whole thread, seems to be close to the
real "problem".
I have two friends who are playing AO together. They often experience
"bad lag" (i.e. 20-30s delays between a command and it's execution).
However, there's one strange thing during these periods of bad lag.
They still chat with each other.
And I've done checking with tcpdump: you do not talk directly between clients.
Everything goes thru the AO servers.
My guess is that their architecture is based on a front-end/zone service
model. Clients connect to a front end, and said front-end connects to a
zone service, depending on the zone you are in. This is further supported
by various analysis points during beta, notably when the zone service
crashed while I was in it (and the whole mission dungeon got resert and
randomly re-rolled), and the numerous problems people have for zoning
(zone... after a strangely fixed 45s - the default TCP connection timeout -
you get "Area Change not initiated on server).
So you have:
Client ---- TCP ----> Front End ---- TCP ----> Zone server
^ /
| /
V /
Client ---- TCP ----> Front End ---- TCP -/
which is probably the worst architecture I can imagine, specially as there
appears to be one front-end per client, and front ends closes and opens
communication to zone servers. :(
><i> In a first step, we would like to know your opinion about this choice. And
</I>><i> in a next step, we'll do some test about ping/packet lost and so on to
</I>><i> compare TCP and UDP, and we'll need your help to do that.
</I>
Packet loss is a non-sequitur under TCP. You *cannot* lose packets under TCP :)
(you lose connection first)
--
Vincent Archer Email: <A HREF="mailto:archer@frmug.org">archer@frmug.org</A>
All men are mortal. Socrates was mortal. Therefore, all men are Socrates.
(Woody Allen)
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