DRdrawkbox·Oct 16, 2014
For the best of both before SCTP exists, if ever, RUDP (Reliable UDP) [1] where needed is what most game developers/engines use on the networking layer such as RakNet [2] (recently bought and open sourced by Oculus), enet [3], and the many based on those.
RUDP or similar systems allow network messaging to ack when needed and unreliable by default which is fine for positional updates with some missing data using interpolation and extrapolation to simulate missing data. Global game states and determining the winner/ending the level might need a reliable call.
With UDP and only some reliable calls you drastically improve real-time performance with less queueing. TCP is ok for turn-based or near-real-time but high action real-time games almost all use UDP with a RUDP twist. Using a mix can also be harmful [4] so the best option is RUDP where
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needed, default to UDP.
UDP is great because it is a broadcast, almost like TV/radio in that you can show the data you receive and smooth the rest. Although, TV/radio needs every data frame to prevent static/lag but imagine the broadcaster having to error check all connections, it would quickly saturate. UDP allows saturation later. Games can predict movement and smooth out missing data for most game actions, you only need a few points for a bezier to be smooth or you might have variables for speed/direction/forces that you can predict with. Pretty good reliability and lack of ordering are not really an issue, if out of order (timestamp older than last) discard and use next or predict until the next valid message (too much of this leads to lag but normal UDP operations it is enough and actually smoother).
[1] https://tools.ietf.org/html/draft-ietf-sigtran-reliable-udp-...
[2] https://github.com/OculusVR/RakNet
[3] http://enet.bespin.org/
[4] http://www.isoc.org/INET97/proceedings/F3/F3_1.HTM