Slashdot Mirror
Taking Halo 2 to Xbox Live
An anonymous reader writes "In this new interview, Bungie Studios engineering lead Chris Butcher explains how his team took Halo 2 multiplayer battles to Xbox Live, with minimal glitches. Turns out there are a lot of clever tricks involved." From the article: "It's actually the same network model we used in Marathon back in the day, although Marathon had some bugs in it. The thing with this networking model is if there's a bug in the computer code where two machines could provide the same inputs but get different outputs, there can be problems. There are lots of different ways that could happen."
... Here ;-)
I still reckon the best game networking in the world is that in Quake and its successors, such as Half-Life and its sequel. Unlike Halo and Halo 2, where co-operative play online was apparently an insurmountable technical challenge, in Quake-based stuff even single-player games are inherently client-server anyway.
From the article, it sounds like Halo 2 multiplayer has moved in that direction away from the all-clients-equal approach of Marathon and Doom, with a single server accepting or denying player-damaging events. Although each client apparently still has a full version of the game world at hand, unlike Quake-style games where a client is only sent relevant stuff - might this allow for some audacious, map-spanning ultra-vision hacks and so on?
Still, that's how they do the recovery thing if the server gets unexpectedly removed from play...
Tedious Bloggy Stuff - hooray?
...because every client is being sent the persistent state of the entities in the world (the entities are what we call the persistent objects in the world), that means that any client has all the information about the world. Because the client knows everything about the world, we can support making them be a new server, if the server machine was to turn off, get disconnected from Xbox Live or the player just wants to leave the game...
Interestingly enough, Bungie's master server and client model is the same model humans use for perceiving the world. For example, right now, Milton Flapdoodle in New Jersey is responsible for perceiving the world, authorizing adjustments to humanity's world view, and beaming the changes to each of us telepathically. Should something happen to Milton, a new server can be chosen because we each carry a copy of the complete world state inside us.
Unfortunately, the technique isn't foolproof and due to the high density of telepathic messages required there is some unexpected bleed-through amongst the clients. You can tell this happens when you witness a profoundly anomalous event like Britney Spears sudden rise in popularity or Brussel Sprouts that inexplicably taste good.
The Marathon quote is referring to Halo 1. Halo 2 is nothing like this, as the article explains.