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May 16, 2023 94 likes •228 views

Vi t Virtual Environments: l E i t Networking Basics g Anthony Steed Anthony Steed Department of Computer Science Department of Computer Science University College London http://www.cs.ucl.ac.uk/teaching/VE Introduction Networks at

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Vi t l E i t Virtual Environments: Networking Basics g

Anthony Steed Anthony Steed

Department of Computer Science Department of Computer Science University College London http://www.cs.ucl.ac.uk/teaching/VE

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Introduction

  • Networks at the heart of networked VR

M t k t l t th

  • Many network protocols are out there

– TCP, UDP, multicast, RTP, etc C – Choice based on needs

  • Programming networking in XVR

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Network properties

  • Latency (Round Trip Time)

Jitt

  • Jitter
  • Bandwidth (Capacity)
  • Loss (Congestion, Reliability)

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Internet Protocol - IP

Application

FTP SMTP DNS SNMP

Transport

TCP UDP

Internet Protocol Transport

IP ICMP IGMP

Data Link

G ARP/RARP Ethernet FDDI

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Ethernet, FDDI

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Protocols: UDP Protocols: UDP

  • Connectionless

No state is maintained – No state is maintained – No setup time Light weight – Light-weight

  • No Quality of Service

Postal Service Postal Service

– No guarantee delivery – No order delivery

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TCP

  • Connection Oriented

– State is maintained at routers – State is maintained at routers – Setup Handshake – Heavy-weight Heavy weight

  • Quality of Service

– FIFO delivery – FIFO delivery – Flow Control – Error Recovery Error Recovery

  • Mechanisms

– Timers Acknowledgements etc Timers, Acknowledgements, etc

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Multicast: Overview Multicast: Overview

WAN

Broadcast

WAN

Unicast

WAN

Multicast

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Multicast: Model Multicast: Model

  • UDP class D address – No physical meaning

M lti t i f LAN

  • Multicast is free on LANs
  • An address defines a logical group
  • A sender is oblivious to receivers
  • Join/Leave operations

Join/Leave operations

  • Tree Based Routing

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Socket

  • End-point for communication

N t k ti b d k t

  • Network connections based on sockets
  • Socket identified by

– Host address – numeric or name – Port number

  • 0-1023 : well known services (e.g. http traffic on 80)
  • 1024-49151: registered ports (less well known)

49152 65536: private applications or dynamic use

  • 49152-65536: private applications or dynamic use

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Socket communication

Listener Client N d t t k t Needs to create a socket to connect t li t i k t Needs to create a socket to listen to incoming connection requests to listening sockets

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The Client/Server logic

Server Client

C t k t f li t i Create socket for listening incoming connections Create socket for connecting to Server Listen Request connection Accept and create thread Send/Receive message Send/Receive message

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XVR functions

Server Client

N tC t Ch lTCP( ) NetCreateChannelTCP( ) NetConnectTCP( ) NetAcceptTCP ( ) Accept and create thread NetSendToTCP() / NetReceiveFromTCP() NetSendToTCP() / NetReceiveFromTCP()

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