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Re: [GNUnet-developers] p2p 'massively multi-player games (MMGs)'

From: Chris GauthierDickey
Subject: Re: [GNUnet-developers] p2p 'massively multi-player games (MMGs)'
Date: Wed, 28 Mar 2007 16:00:19 -0600

So, for your latency question, I would have to say that "it depends on what do
you want to do". See, there are really no implementation for it at the
moment, or something for us to test that. What we have is in GNUnet's roadmap one application called "gnunet-chat", that does exactly that: swaps messages
between nodes. When that's built we'll be able to see the real latency
challange in GNUnet, but, otoh, we believe that gnunet-chat <will work>, and, depending on what kind of stuff you're wanting to do, that can already be
enough. Most MMOG's send little more traffic than a simple chat system
does... Unless you try to use the network to send graphics data.

Most multiplayer games are aimed to take advantage of the available hardware that players have. The networking is tweaked to prevent the bandwidth from being overloaded and the servers do a few fancy tricks to send only the most important data if the data to be sent is more than what the player's bandwidth can handle.

In essence, most MMOs will target network utilization for around 80-90% of a 56k modem (we can see this from measurement experiments). I think we can expect to see this increase as the population that has broadband increases to the majority of players. So I wouldn't say MMOs send little more traffic than a simple chat system (though it'd be impressive if someone could chat at 48kbps!).

The main issue here is the topology of the network. As I stated before, we have limits on latency given a particular type of game. We can probably assume that bandwidth will continue to increase at the end-user over time, so bandwidth is not as much of an issue. With games, it's about latency, update frequency, and security. If the topology of the network is not conducive to fast message dissemination, then it's fairly easy to show that it won't be able to support a particular
type of game.

If you look at the current research in this area, many of the P2P systems use structured overlays, such as Pastry. This introduces a logarithmic number of
hops from point A to point B. However, these are end-system hops, not
network level hops, and therefore cause a significant amount of latency that
make the most common type of commercially successful games unplayable.

On the other hand, a pure P2P network with all-to-all message passing is clearly not viable either. One of the things I'm looking at is building the P2P network based on the locations of players in the virtual world. Thus, instead of randomly organizing players into the network, where a message between two players that are close in the virtual world might have to traverse the entire network, the message will instead take only a single, direct hop to the other player, or at least minimize
the number of hops required.


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