22-12-2012, 06:54 PM
IP MULTICAST and MULTICAST ROUTING
IP MULTICAST.ppt (Size: 638 KB / Downloads: 23)
Basic Concepts
Each device in network is identified by IP address(32 bit).
IP address is unique address.
Total number of addresses used by a protocol is known as address space.
Address space of Ipv4=232
address space in case of IPv6=2128
IP multicast Addressing
Unicast, multicast,multiple unicast and broadcast.
any packet can be send in unicast way in which packet start from source S1 and passes through routers to reach at destination D1 . Only one interface is used by any intermediate router.
In case of multicast packet is sending from one source to many (group) of destinations.
Destination address is group of addresses .
Multicast addresses are only used for destination hosts not for source.
Several interfaces are used in muticast routing of packet
Broadcast routing of packet is one to all .
In multiple unicast several packets sends from source each with different unicast destination address.
IP Multicasting
Address assignment:
Class D adresses are used for multicast routing of packets . There is address assignment mechanism in IP multicasting to assign address space of class D to specific member.
there are two catagories of address assignment in multicasting
Time To Live (TTL)
Scope-limiting parameter for IP Multicast datagrams
Controls the number of hops that a IP Multicast packet is allowed to propagate
TTL = 1: local network multicast
TTL > 1: Multicast router(s) attached to the local network forward IP Multicast datagrams
Flooding
When a router receives a multicast packet for a group, it determines if it is the first time it has seen the packet
Then, it forwards it on all interfaces except the incoming interface.
Routers only need to store recently seen packets
Reverse Path Multicasting (RPM)
Creates a delivery tree that spans only:
Subnetworks with group members, and
Routers and subnetworks along the shortest path to subnetworks with group members
Allows the source-rooted tree to be pruned
The first packet is forwarded using TRPB
Downstream routers send Prunes if they have no members
Periodically refresh pruned tree using TRPB
Lim: Scalability