Internet Multicast

Internet Multicast 

Broadcast address ( all 1's  )reserved for sending to all station simultaneusly

Multicast

• A limited form of broadcast
• A subset of the computer on a network agree to listen to given multicast address
• The set of participating computer is called multicast group
• A computer should instruct its host interface to accept froup's multicast address for joining a multicast group

IP MULTICAST
Internet abstraction of hardware multicasting
General characteristics:-

Group address
Each multicast group is unique class D address

• →A few IP multicast address are permenently assigned by internet authority
• →Other addresses are temporary and are available for private use

Number of groups
IP provides address for upto 2^28 simultaneous multicast groups

Dynamic Group membership
A host can join or leave an IP multicast group

Use of hardware
If hardware does not support multicast .IP uses broadcast or unicast to deliver IP multicast

Inter-network forwarding
Membership of an IP multicast group can attach to multiple physical network ,special multicast routers are required to forward IP multicast

Delivery semantics
Multicast datagram can be lost ,delayed ,duplicated or delivered out of order

Membership transmission
Group membership is only used to determine whether the host receives datagram sent to the group

IP MULTICAST ADDRESS

IP multicast addresses are divided into two types

• Those are permanently assigned
• Those are temporary use

Permenent Address
Permanent address are called well known
They used for major service on the global Internet also as well as used for infrastructure maintenance

Temporary address
It correspond to transient multicast group
They are created when needed ,discarded when the count of group member reaches zero
IP reserve class D address for multicast