We then met with Yahn Bernier, who gave us a summary of the work he's done with Half-Life's networking code. Having Quake, Quake II, and Quakeworld's codebase to work on over the last two years, Yahn was quick to catch onto the quandary of interpolated vs. extrapolated networking. To the great relief Quakeworld fans, Valve chose to work with the extrapolated model, giving clients a much more responsive, precise feel. They've also done more work on the bandwidth reduction side, moving all non-critical animations and effects to the client side. Whereas the server controlled the rotating of the weapons and armor in Quake, a HL server will merely tell the client that armor is present, and any accompanying animation is handled directly from the client. This means that non-critical animations may not appear identical on each client (death animations may differ and the like), but the benefits may be happily reaped by those not fortunate enough to have cable modem or ISDN.
He wasn't as new-age as I thought he would be
Valve has also taken the effort to make multiplayer as simple as possible - one click and you're in. What they've done is integrated each client into Sierra's WON network - you immediately have access to all of the servers polled by WON, and you can hop into any game effortlessly. They also provide an integrated server-locator utility, sort of a "gamespy lite," which allows you to ping external servers, add your favorite servers, and more. No more having to alt-tab out of the game and refresh your server list when the local competition evacuates the server.