multiplayer network technology
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TRANSCRIPT
Introduction toMultiplayer Network Technology
Thomas Lidy
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Introduction
Networking - used in ...– e-commerce– training & education– distributed engineering & design– entertainment– multi player games „networked virtual environments“
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Networked Virtual Environment
software system– multiple users interact in real-time– shared sense of space and time– realistic 3D graphics and sound– a way to communicate– interaction with the virtual environment
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Networked Virtual Environment
components– graphics engines and displays– communication and control devices– processing systems– data network
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Origins of virtual environments
origins in military (and industry)
academic research in networked virtual environments
virtual worlds on PC class systems- 3D games
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Origins in military
SIMNET– started 1983– developed for DARPA
DIS (protocol)– defined after 1989– standardized packets (PDUs)– distributed & heterogeneous
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Origins in industry
SGI - Flight (1984) SGI - Dogfight (1985)
Academic origins NPSNET (1986) PARADISE (1993) BrickNet (1991)
Flight
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Origins on PC class machines
Doom (1993) Macintosh: Marathon (1994) Bolo (tank game)
Doom
... and many othersBolo
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Network Technology
Issues for networking– Latency
time required from one host to another– Bandwidth
data rate: how many bits per second– Reliability
how much data is lost
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Sockets and Ports
allow multiple applications to use the network
TCP
0 65535
UDP
0 65535
Other Prot.
0 65535
Applications ftp www netVEs games
IP (Internet Protocol)
port #s
protocols
IP layer
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Internet Protocol (IP)
low-level protocol basic services splits & reassembles packets TTL field („time to live“) other protocols lie on topon top of IP
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Transmission Control Protocol (TCP)
layered on top of IP ( TCP/IP) simple point-to-point connection automatic acknowledgments error checking correct packet order reliability
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User Datagram Protocol (UDP)
also layered on top of IP connectionless packet-by-packet basis best-efforts delivery (not reliable) less processing time faster deal with packet loss and ordering!
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IP Broadcasting
instead of sending multiple copiesof a packet to all destinations
single transmission to allall hosts in the network
broadcasting to address 255.255.255.255 disadvantages:
– expensive for hosts that are not interested– delivery only on LAN - not Internet-wide!
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IP Multicasting
receiver-controlled distribution interested hosts subscribe to a list packets are sent down distribution
paths no burdens for hosts not interested less overhead than broadcasting appropriate for Internet use
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Multicast routing
LondonWashington
Vienna
Moscow
TokyoDenver
New York
MunichPrague
Graz
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IP Multicasting
addressing– pseudo IP (class D address):
range 224.0.0.0 - 239.255.255.255– can be used temporarily or reserved by IANA
problems– routers must be multicast-capable– not yet available troughout the Internet multicast routers communicate directly with each
other through the MBONE
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Overview (1)
TCP UDPdelivery: guaranteed best-effortflow: stream-based packet-basedordering: ordered
packetsimmediate
deliveryerror handling: checksums -advantages: reliable low overheaddisadvant.: delays,
overheadno ordering,no acknowl.
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Overview (2)Broadcasting Multicasting
delivery to: all hosts onlocal network
subscribed hosts
strengths: fast delivery,as with UDP
efficient Internet-wide delivery
limitations: same as UDP,limited to LAN
same as UDP,routers must bemulticast-capable
suitable for: small-scale p2pnetVEs withhigh datarequirements
large-scale p2pand client/servernetVEs in theInternet
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Networking today - Conclusion
networking:essential part of multi player environments
designers must carefully selectprotocols and network archtitecture
multicasting: most efficient technique for large-scale netVEs
games today use client/server, peer-to-peer multicasting probably becomes more globally
available with IPv6
Thomas Lidy
The EndThe End