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Simple question about bandwidth

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I've been reading up on bandwidh in network programming, and I've read in a book that upstream bandwidth and downstream bandwith are both used in the data I'm sending. Thusly, if my limit is 8KB I can only send 4096 bytes upstream, and 4096 bytes downstream per second. Is this right? Perhaps I've misread something. If that's true, I'd be murdered from my assessment of things. I had thought my limit was separate for upstream and downstream.

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uhh you shouldn't ever rely on what you *should* be able to send 'cause all connections are different. that being said, upstream and downstream and seperate.

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Good to know! Perhaps I'll do a bit of rereading.

Thanks!

Update: If anyone is wondering the book is Multiplayer Game Programming on page 88.

"If you take 7,075 bytes per second and divide that around 60, you find that only around 118 bytes can be transmitted per frame. You need a total bandwidth of 118 bytes per frame for both receiving and transmitting; therfore, you really only have 118 divide by 3, or 59 bytes, available to send and receive per frame."

I'll note that this is information based on a 56k modem and the book is around 7 years old.

[Edited by - AntiGuy on July 30, 2008 11:14:46 AM]

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You don't send data from the client at 60 fps. I normally send it at around 10 times per second. Data coming from the client to the server isn't really problem. (Not to mention if you only send delta packets the number is ridiculously small it doesn't even matter).

It's when you send it out from the server that you begin seeing bandwidth calculations that matter. Things like groups of units become N^2 bandwidth problems and such. (Again optimizing and things like delta packets cut a lot of that down).

Only send data from the client or server at a given rate. For instance, server to client for a real-time game is around 10 times per second. Updating from the client to server can be almost anything especially if you are using delta packets. From quick testing and stuff anything over 10 times per second is usually overkill though. So you end up with stuff like 100 ms send rates.

http://www.speedtest.net/ <--- go there and run a test to see your bandwidth. Or have someone with 56k test it. (Been a long time since I've seen 56k).

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If I remember correctly, the 56k modems could only send in one direction at a time, because of the way that phone wiring works (sender and receiver make up one closed loop with a fixed bandwidth). If you have a multi-player game, you need to send all data for yourself, and receive all the data for the other players, at a minimum (with P2P, you may have to send more than that).

So, in the context that the text seems to describe, the statement is probably true. For anyone with broadband, though, downstream and upstream are separate channels.

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