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| author | neodarz <neodarz@neodarz.net> | 2018-08-11 20:21:34 +0200 |
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| committer | neodarz <neodarz@neodarz.net> | 2018-08-11 20:21:34 +0200 |
| commit | 0ea5fc66924303d1bf73ba283a383e2aadee02f2 (patch) | |
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diff --git a/pipermail/nel/2001-July/000494.html b/pipermail/nel/2001-July/000494.html new file mode 100644 index 00000000..5eb1404d --- /dev/null +++ b/pipermail/nel/2001-July/000494.html @@ -0,0 +1,138 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<HTML> + <HEAD> + <TITLE> [Nel] TCP vs. UDP</TITLE> + <LINK REL="Index" HREF="index.html" > + <LINK REL="made" HREF="mailto:svferro%40earthlink.net"> + <LINK REL="Previous" HREF="000492.html"> + <LINK REL="Next" HREF="000496.html"> + </HEAD> + <BODY BGCOLOR="#ffffff"> + <H1>[Nel] TCP vs. UDP</H1> + <B>Sal</B> + <A HREF="mailto:svferro%40earthlink.net" + TITLE="[Nel] TCP vs. UDP">svferro@earthlink.net</A><BR> + <I>Fri, 6 Jul 2001 18:32:46 -0400</I> + <P><UL> + <LI> Previous message: <A HREF="000492.html">[Nel] TCP vs. UDP</A></li> + <LI> Next message: <A HREF="000496.html">[Nel] TCP vs. UDP</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#494">[ date ]</a> + <a href="thread.html#494">[ thread ]</a> + <a href="subject.html#494">[ subject ]</a> + <a href="author.html#494">[ author ]</a> + </LI> + </UL> + <HR> +<!--beginarticle--> +<PRE>><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>><i> +</I>><i> Vianney Lecroart +</I> + I've coded small scale 3d client/server systems in both TCP and UDP +while developing software for Worldforge, and have playtested both systems. +The end result was that UDP gameplay just seemed smoother, especially under +low latency/bad connections. Even when I had inserted code to purposely +drop packets, gameplay was still surprisingly bearable. + + On my LAN or for persons with fast links to the server TCP was not +really noticeably slower, though. So with very low latency, and little +packet loss TCP would be the better choice, but unfortunately that isn't the +case for the internet just yet. A lot of people are behind slow links, +shared internet connections, or in unfortunate locations... for some people +overseas my TCP-based software was almost unplayable, where UDP was still at +least minimally usable. If you guys do end up benchmarking TCP vs. UDP, be +sure to test over a simulated low-latency, and/or 'noisy' link. Drop +packets randomly, simulate possible internet conditions. I'm sure you will +come to the same results I did. + + The majority of problems I've had with UDP are firewall related. And +they were almost all serverside, ie a person trying to run a UDP server +behind a firewall and unable to map ports/etc. to let clients connect. +Clientside, however there was very little trouble, it worked through my +ipmasq firewall without problems, for one, and others had been testing +behind firewalls also. + + However, a bit of 'reinventing TCP' was needed for the reliable data. +This is unavoidable, some messages need to be sent and can't be +ignored/dropped. And I agree that the OS's TCP implementation is probably +more efficient than one drawn up for a video game. But I don't think using +both UDP and TCP is worth the trouble to gain a reliable data transmission +stream. I just don't think the performance improvement would be significant +enough to justify the implementation... Let me explain why I think so. + + Now, say you were sending a 10 MB file over the internet to a friend. +_Every_ packet must make it to the peer or the file would be corrupt. Every +packet must be acknowledged somehow, using some crc, sequence number... etc. +I haven't looked at any actual TCP implementation's source code, but I'll +bet it does all sorts of compromising between packet transmission and +acknowledgement frequency, message sizes, etc. and over the course of +sending 10 Million packets (ok, maybe less for a 10 MB file) it probably +saves a considerable amount of time over some dumb UDP code that +acknowledges say, every 10 packets or some other simplistic mechanism. + + Yes, in that situation, reinventing TCP would be a bad idea... and yes, +it is definately a better choice than UDP, which in fact is why almost every +internet protocol uses TCP. But in our case we aren't sending a 10MB file, +we're sending short messages to tell the client/server something important. +ie a 'player X has died' message, which could be maybe a dozen bytes in +size. All the fancy optimization that an OS's TCP stack does over the course +of time wouldn't be of much use here. Also, in sending a 10MB file you dont +care about latency, and you know what the next few thousand packets are +going to consist of beforehand, whereas in a video game this is not the +case. The optimizations TCP gives you would only take effect if you were +sending large, continuous blocks of data. + + So for the gameplay networking layer I suggest UDP. The only exception +in my opinion is for things like automatic client-patching, or downloading +of media. In that case, having the client make an HTTP connection to a web +server, or something similair is a *much* better choice than using the +'gameplay networking' layer to send this data. + + The software I spoke of here is all in Worldforge's (www.worldforge.org) +CVS repository. The software I tested with was XClient, and XServer, which +are both in CVS. + + The UDP networking library I created and used in XClient/XServer, which +I recommend taking a look at, is called 'XUDP' (not the library that Dave +posted about, but has the same name :-/) is also in Worldforge CVS. I +extracted the UDP networking code from the GPLed Quake1 src, and converted +it into a general C++ OO UDP networking library. It contains code for both +reliable and unreliable transmission of data. Credit should go mostly to +John Carmack of Id software for the code. I just abstracted, and tweaked a +bit for use in an MMORPG setting. It might be helpful if you guys decide to +go with UDP for Nel. + + Anyway, sorry for the long winded rant. Hope this helps some, and keep +up the great work! + +- Sal + + + + + +</pre> + + + + + + + +<!--endarticle--> + <HR> + <P><UL> + <!--threads--> + <LI> Previous message: <A HREF="000492.html">[Nel] TCP vs. UDP</A></li> + <LI> Next message: <A HREF="000496.html">[Nel] TCP vs. UDP</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#494">[ date ]</a> + <a href="thread.html#494">[ thread ]</a> + <a href="subject.html#494">[ subject ]</a> + <a href="author.html#494">[ author ]</a> + </LI> + </UL> +</body></html> |