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Multicast

Multicast. Integrated Network Services Almerindo Graziano. Introduction. New applications Type of communications Shortfalls of Unicast Multicast IP Multicast IP Multicast sessions Example Conclusions. New Applications. Improved computer systems New types of applications:

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Multicast

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  1. Multicast Integrated Network Services Almerindo Graziano

  2. Introduction • New applications • Type of communications • Shortfalls of Unicast • Multicast • IP Multicast • IP Multicast sessions • Example • Conclusions

  3. New Applications • Improved computer systems • New types of applications: • Point-to-Multipoint • Multipoint-to-Multipoint • Computer networks do not keep the pace

  4. Multiple-Destination Applications • Videoconferencing • Remote seminars • Transmission of corporate messages to employees • Live transmission of multimedia training • Communication of stock quotes to brokers • Transmission over networks of live TV or radio news

  5. Unicast • Problems of using Unicast: • Lack of Bandwidth • Need more powerful workstations • Difficult to manage with multiple destinations • A possible solution: • Multicast

  6. D1 D2 . . . . . BT = B BT = N x B S D S: Source D: Recipient BT: Total Bandwidth involved B: Bandwidth required by one recipient DN Unicast Transmission

  7. IP Multicast • IP Multicast (Steve Deering 1989, RFC112) • Greatly reduces the used bandwidth • Reduces the load on the servers • It’s receiver initiated • Introduces the concept of Session

  8. IP Multicast • Host groups (logical addressing) • Multicast Sessions • IGMP (Internet Group Management Protocol) • It works better on broadcast media

  9. IP Multicast Addresses • Class D Internet Protocol addresses: • 224.0.0.0 to 239.255.255.255 • 224.0.0.0 to 224.0.0.255 are reserved: • 224.0.0.1 is all host groups • 224.0.13.0 to 224.0.13.255 for Net News

  10. Receivers Sender R BT = B BT = B BT = B BT = B R R R Internetwork S: Source D: Recipient BT: Total Bandwidth involved B: Bandwidth required by one recipient Multicast Transmission

  11. IP multicast over 802 LANs • IP unicast address  MAC address • IP Multicast address  multiple MAC addresses? • IEEE assigns 01-5E-00-00-00 to the IETF for Multicast • Low-order 23 bits of IP Multicast address  low-order 23 bits of MAC address 01-5E-00-00-00 • Mapping is not unique

  12. MAC address format 8 7 6 5 4 3 2 1 O U/L I/G Byte 1 U Byte 2 I Byte 3 Byte 4 Manufacturer Byte 5 Byte 6

  13. Mbone (IP Multicast Backbone) • Virtual network layered on top of the Internet (IETF July 1992) • Is made of multicast island • Communication between islands is achieved via tunnels

  14. Mbone Topology Multicast Router Tunnels LAN Multicast Island

  15. Mbone Map (1994)

  16. LAN A LAN B MRA MRB Tunnelling

  17. Transmission on the Mbone

  18. References • http://www.mbone.com • http://www.ipmulticast.com • http://www.video.ja.net/mice

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