Tài liệu The TRIBES Engine Networking Model or How to Make the Internet Rock for Multiplayer Games by Mark Fr

The TRIBES Engine Networking Model or How to Make the Internet Rock for Multiplayer Games by Mark Frohnmayer and Tim Gift Mark

Abstract
This paper discusses the networking model developed to support a
realtime
multiplayer
gaming environment. This model is being
developed for TRIBES II, and was first implemented in Starsiege
TRIBES, a multiplayer
online team game published in December
'98. The three major features of this model are: support for
multiple data delivery requirements, partial object state updates
and a packet delivery notification protocol.
Overview
Starsiege TRIBES supports two modes of play: single player or
multiplayer
over a LAN or the Internet. The multiplayer
mode
supports up to 128 human or AI controlled players in a single
game. Performance over the Internet drove the design of the
networking model. The model supports low end modem connections
and is designed to deal with low bandwidth, high latency and
intermittent packet loss.
The model deals primarily with the delivery of data and a key
concept is the classification of delivery requirements.
All data is classified into one of several requirement categories
and the design of each component in the model centers around
meeting those requirements. We organize transmitted data as
follows:
1. Nonguaranteed data is data that is never retransmitted if lost.
2. Guaranteed data is data that must be retransmitted if lost,
and delivered to the client in the order it was sent.
3. Most Recent State data is volatile data of which only the
latest version is of interest.
4. Guaranteed Quickest data is data that needs to be delivered in
the quickest possible manner.
The networking model is divided into three major components as
shown in Figure 1:
1. A Connection Layer that deals with notification and delivery
of packets between client and server. The features of this
layer along with a stream class provide the general
infrastructure on which the other layers are built.
2. A Stream Layer which provides packet stream management. This
layer employs five stream managers to deal with events, object
mirroring, input move management, static data and string
compression. Each of the five stream managers provides
different data delivery guarantees.
3. A Simulation Layer which manages all objects in the
simulation. A full description of this layer is outside the
scope of this article but several items are relevant: the
advancement of time, object scoping and client prediction.