The present invention provides a network support mechanism, called
Sync-VPN, that is transparent to real-time, multi-user distributed
applications, such as online multi-player games in which the order of
player actions is critical to the outcome. The invention uses a
client/server application model, where a server coordinates state updates
based on action messages sent by clients. The invention builds on
bandwidth-quaranteed VPN service to ensure predictable packet delay and
loss characteristics, thereby providing predictable packet service, state
update fairness, and player action fairness. A Sync-out mechanism
synchronizes delivery of state updates to all players enabling them to
react to the same update fairly. A Sync-in mechanism processes action
messages from all players in a fair order based on real-time occurrence.
Sync-VPN employs a round-trip time estimation algorithm essential to
message latency estimation in the Sync-out and Sync-in mechanisms.