7_Multicast&Realtime_spring10

7_Multicast&Realtime_spring10 - Chapter 7 Multicast...

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TCP/IP Essentials A Lab-Based Approach Chapter 7 Chapter 7 Multicast and Real Multicast and Real - - Time Service Time Service Spring 2010
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Polytechnic Institute of NYU Slide 2 zjzhao Multicast • Multicasting is one-to-many or many-to-many communications. • A simple implementation of multicasting can be built on top of the unicast (point to point) service … – Each multicast source send N-1 copies for total N members in the multicast group that leads to an inefficient N 2 problem – The desired case: a packet should be transmitted on one link exactly once (for the least packet replication in network) • IP Multicasting uses less network resources. • IP supports multicasting via the help of IGMP and additional routing protocols. Unicast Broadcast Multicast Anycast
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Polytechnic Institute of NYU Slide 3 zjzhao IP Unicast and Multicast When A wants to send a packet to B, C and D •U n i c a s t – A sends three copies of the packet, each to a different address. – Each copy may take a different path. – For a group of N nodes, N(N- 1)/2 paths are needed. • Multicast – A sends one copy of the packet to a group address. – The packet will be forwarded in a multicast tree to B, C and D. – Less network resources are used.
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Polytechnic Institute of NYU Slide 4 zjzhao IP Multicast Supported Services DNS multicast query: provides a way to locate nearby domain name servers without knowing their IP addresses. The Recursion Desired bit should not be set in order to avoid excessive load on both network and DNS servers. RIPv2 multicast RIP messages only to RIP routers (224.0.0.9) instead of to all routers in RIPv1. SNMP implementation can use multicast to support group communication between managers and broker agents. ICMP router solicitation and router advertisement: a host can multicast an ICMP router solicitation massage to all routers in this subnet (specified by 224.0.0.2) after bootstrapping to build its routing table. IP Multimedia Streaming for video teleconferencing, Internet audio, IPTV, and video streaming.
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Slide 5 zjzhao IP Multicasting Key Components • Multicast group management – The multicast group is dynamic, meaning that users may join and leave the group during the multicast session. – A multicast router needs to keep track of the memberships of all the multicast groups. – A participant may want to know who else is in the group. • Multicast addressing – Define a common group IP address for all nodes in each multicast group. – Map a multicast group IP address to a MAC address of layer 2 network • Multicast routing – Find and maintain a multicast tree from one participating node to all other nodes in the group. – The tree should be updated when
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7_Multicast&Realtime_spring10 - Chapter 7 Multicast...

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