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

DN D S D2 D B T = BB T = N x B S: Source D: Recipient B T : Total Bandwidth involved B: Bandwidth required by one recipient Unicast Transmission

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: – to to are reserved: – is all host groups – to for Net News

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

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

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

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

Multicast Router Tunnels Multicast Island LAN Mbone Topology

Mbone Map (1994)

MRAMRB LAN ALAN B Tunnelling

Transmission on the Mbone

References