2. Introduction to Multiplayer Network Technology Thomas Lidy

3. 2/20 Thomas Lidy Introduction to Multiplayer Network Technology Introduction n Networking - used in... – e-commerce – training & education – distributed engineering & design – entertainment – multi player games –  „networked virtual environments“

4. 3/20 Thomas Lidy Introduction to Multiplayer Network Technology Networked Virtual Environment n 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

5. 4/20 Thomas Lidy Introduction to Multiplayer Network Technology Networked Virtual Environment n components – graphics engines and displays – communication and control devices – processing systems – data network

6. 5/20 Thomas Lidy Introduction to Multiplayer Network Technology Origins of virtual environments n origins in military (and industry) n academic research in networked virtual environments n virtual worlds on PC class systems - 3D games

7. 6/20 Thomas Lidy Introduction to Multiplayer Network Technology Origins in military n SIMNET – started 1983 – developed for DARPA n DIS (protocol) – defined after 1989 – standardized packets (PDUs) – distributed & heterogeneous

8. 7/20 Thomas Lidy Introduction to Multiplayer Network Technology Origins in industry n SGI - Flight (1984) n SGI - Dogfight (1985) Academic origins n NPSNET (1986) n PARADISE (1993) n BrickNet (1991) Flight

9. 8/20 Thomas Lidy Introduction to Multiplayer Network Technology Origins on PC class machines n Doom (1993) n Macintosh: n Marathon (1994) n Bolo (tank game) Doom n... and many others Bolo

10. 9/20 Thomas Lidy Introduction to Multiplayer Network Technology Network Technology n 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

11. 10/20 Thomas Lidy Introduction to Multiplayer Network Technology Sockets and Ports n 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

12. 11/20 Thomas Lidy Introduction to Multiplayer Network Technology Internet Protocol (IP) n low-level protocol n basic services n splits & reassembles packets n TTL field („time to live“) on top n other protocols lie on top of IP

13. 12/20 Thomas Lidy Introduction to Multiplayer Network Technology Transmission Control Protocol (TCP) n layered on top of IP (  TCP/IP) n simple point-to-point connection n automatic acknowledgments n error checking n correct packet order n  reliability

14. 13/20 Thomas Lidy Introduction to Multiplayer Network Technology User Datagram Protocol (UDP) n also layered on top of IP n connectionless n packet-by-packet basis n best-efforts delivery (not reliable) n less processing time  faster n deal with packet loss and ordering!

15. 14/20 Thomas Lidy Introduction to Multiplayer Network Technology IP Broadcasting n instead of sending multiple copies of a packet to all destinations all n single transmission to all hosts in the network n broadcasting to address 255.255.255.255 n disadvantages: – expensive for hosts that are not interested – delivery only on LAN - not Internet-wide!

16. 15/20 Thomas Lidy Introduction to Multiplayer Network Technology IP Multicasting n receiver-controlled distribution n interested hosts subscribe to a list n packets are sent down distribution paths n no burdens for hosts not interested n less overhead than broadcasting n appropriate for Internet use

17. 16/20 Thomas Lidy Introduction to Multiplayer Network Technology Multicast routing London Washington Vienna Moscow Tokyo Denver New York Munich Prague Graz

18. 17/20 Thomas Lidy Introduction to Multiplayer Network Technology IP Multicasting n addressing – pseudo IP (class D address): range 224.0.0.0 - 239.255.255.255 – can be used temporarily or reserved by IANA n problems – routers must be multicast-capable – not yet available troughout the Internet –  multicast routers communicate directly with each other through the MBONE

19. 18/20 Thomas Lidy Introduction to Multiplayer Network Technology Overview (1)

20. 19/20 Thomas Lidy Introduction to Multiplayer Network Technology Overview (2)

21. 20/20 Thomas Lidy Introduction to Multiplayer Network Technology Networking today - Conclusion n networking: essential part of multi player environments n designers must carefully select protocols and network archtitecture n multicasting: most efficient technique for large-scale netVEs n games today use client/server, peer-to-peer n multicasting probably becomes more globally available with IPv6

22. Thomas Lidy The End