what is the typical client-server game network bandwidth? no matter what type of game we design, the approach of data transfer is similiar: - client sends it's own actions to the server, which then verifies them and sends back to all other clients assuming the server would be able to hold up to 32 clients, what is the typical amount of bytes sent by the client by every frame to the server, and then, bytes sent by the host to all connected clients? I realise it depends on if it's RTS/Action/Turn based game, but are we talking here about dozens of bytes, or up to 1kb, or even more ? cheers!

Roundbased: A few bytes/sec
RTS: A bit more, probably. But only if you only send around player input. If you synchronise each unit independently it will be a lot more.
Action (as in FPS): Depending on the number of players: 1-8k/sec down, 1-2 kb/sec up on clientside

These are all estimated and depend a lot on how you implement it and how much data you have for synchronisation.

2k up for a racing or fps style game wouldn't be unusual. The major factor is likely to be the prediction system and hence the number of updates per second required. Most titles send very little in the way of useful data per second, its all down to the eth/ip/udp headers.

The download rate will be greater but scales well if the packets are collated to a sensible degree.

Let's assume you want a guy with a 1.5/384 kbps DSL line to host an 8 player game, and a 1.5/1.5 T1 line to host 32 players.

The math says that the bandwidth usage (including packet overhead and re-sends) is < 48 kbps per player connection.

With 32 players, at 48 kbps, you need to keep under 1500 bps per player of downstream data, which means you probably aren't sending much more than that upstream from each client.

Thus, the game is likely playable (but not hostable) on a modem.