Transcript 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: – Point-to-Multipoint – Multipoint-to-Multipoint • Computer networks do not keep the pace 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 Unicast • Problems of using Unicast: – Lack of Bandwidth – Need more powerful workstations – Difficult to manage with multiple destinations • A possible solution: – Multicast Unicast Transmission D1 D2 BT = B S BT = N x B . . . . . D S: Source D: Recipient BT: Total Bandwidth involved B: Bandwidth required by one recipient DN 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 IP Multicast •Host groups (logical addressing) •Multicast Sessions •IGMP (Internet Group Management Protocol) •It works better on broadcast media 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 Multicast Transmission Receivers Sender R BT = B BT = B BT = B BT = B R R Internetwork S: Source D: Recipient BT: Total Bandwidth involved B: Bandwidth required by one recipient R 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 loworder 23 bits of MAC address 01-5E-00-00-00 – Mapping is not unique MAC address format 8 7 6 5 4 3 2 1 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 O U/L I/G U I Manufacturer 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 Mbone Topology Multicast Router Tunnels LAN Multicast Island Mbone Map (1994) Tunnelling LAN A LAN B MRA MRB Transmission on the Mbone References • http://www.mbone.com • http://www.ipmulticast.com • http://www.video.ja.net/mice