The most common complaint from on-line gamers is that they experience too high a lag or ping time (technically known as the round trip time, RTT, usually measured in milliseconds) when playing games connected to an on-line game server via a cable modem. Often the lag times they complain of from their game are far higher than the RTTs measured by system commands such as ping or tracert. Games users often also report suffering from higher packet loss than detected by system utilities.
Possible causes of high ping times and packet loss in on-line games are that:
The game's network traffic is exceeding the cable modem's rate cap, and the cable modem itself is therefore causing network traffic to be delayed;
The game's network traffic is exceeding the game server's per-client rate cap - a mechanism which can be used by server admins to limit the natural advantage that cable/DSL users have over slow modem users.
For instance, Barrysworld servers set a rate cap of 10000 bytes per second. A possible cause of this is that some games, when they detect that (or are told that) the connection is via ethernet or USB, automatically switch themselves into a configuration designed for a 10Mbps LAN connection, where very high network traffic is possible.
The game is ignorant of the rate capping in the cable modem, and overloads the connection, causing the lag. The rate capping in the cable modem will generally be non-destructive for TCP traffic, but many games use UDP (unreliable datagram protocol), where rate capping can lead to packet loss as well as high ping times.
The downstream and upstream network demands of a game are reasonably symmetric, whereas cable modem rate caps are not, so it is the lower upstream rate cap that affects game-players most.
Therefore, many network games require their configuration to be tweaked so thatthey are aware that the cable connection is slower than a normal LAN connection. You should tweak the game down to the safe throughput of your upstream connection: for instance a 128kbps upstream can sustain only about 12000 bytes per second before rate-capping begins to take effect, and even that assumes a clear network path to an uncapped server: if the network is congested, or the server capped, a lower value will be required. Many game service providers cap the per-client data rate at 10000 bytes per second, so there is no point trying higher than this.
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