Quote:Where can i find complete book or information about making a multiplayer game & it's architecture.(May server or servers will never handle 100000 number of players.i don't intend this.Mostly 7500 (which i doubt will never come to this number)
What Network & ai libraries do u suggest?How can i find comprehensive info about this?

There are no books on this. At least not top to bottom type.

Also, multiplayer game is one that cannot have more than 64 or so players per game.

Anything else is MMO. Especially since you're talking about clustering. 500 is reasonable, although not unproblematic. Thousands will require decent clustering solution. The reasonable limit is hundreds of players per single cluster node. A somewhat practical limit is 200-300 players in area of interest (what client sees).

100,000 hasn't been done before, except possibly in military simulations.

Quote:does multiplayer games use something like this.(if they don't..how can they prevent fraud/cheatting)

This is a topic as large as developing an MMO itself. It comes down to just about every aspect, from connection management, transactions, extreme validation, integrity checks, solid design, ....

Keep in mind that business application that handle 500 users are a far cry from a real-time interactive server. The challenges are completely different, although technologies used are similar.

The comprehensive info you'll need is clustering, TCP and UDP fundamentals, insane ammount of testing and experimentation, solid understanding of databases and a lot of time. The only known case (to me) where a single person (1 developer, 1 artist, 1 other) developed an MMO-grade game took around a year, and relied solely on third-party software. I believe the game peaked at several hundred accounts.

There's also MMORPG emulators out there, but I have yet to see of one that would be actually production quality, or written for the needs of actually developing an MMO, not just feeding the client. In addition, there are several somewhat accessible frameworks for MMORPG development.

Also, unless you'll be using complete third-party solution, you'll quickly find yourself faced with problems never encountered in bussiness environment. A 300ms lag spike in a business application isn't even accounted for. 300ms spike in a game can make it unplayable. 2 such spikes every 10 seconds will make players give up.

The best of the information you'll find here is in the networking forum FAQ. There's also plenty of aspects covered in Game Programming Gems book series.