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How do I subscribe to a multicast group?
To join a multicast group, a host sends a join message, using the Internet Group Management Protocol (IGMP), to its first-hop router. Groups are identified by a single class D IP address (in the range 224.0. 0.0 to 239.255. 255.255).
How does multicast subscription work?
Using multicast, a source can send a single copy of data to a single multicast address, which is then distributed to an entire group of recipients. A source host sends data to a multicast group by simply setting the destination IP address of the datagram to be the multicast group address.
How are multicast addresses assigned?
Multicasting has its own Class D IP addressing scheme, controlled and assigned by the Internet Assigned Numbers Authority (IANA). This means that all IP multicasts are in the range of 224.0. 0.0 to 239.255.
What is multicast group membership?
A multicast group is defined by an IP address and a port number. Once a host has group membership, the host will receive any data packets that are sent to that group defined by an IP address/port number. This is the case of Figure 4.30 (Top Right) where host D sends a data packet to the group without being a member.
What is a multicast address used for?
A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service.
How many hosts can be part of a multicast group?
A host that is configured to receive datagrams sent to a multicast address becomes part of a multicast group for that address. A group can have 1 to an unlimited number of hosts. Neither hosts or routers maintain a list of individual group members. A host can be part of multiple multicast groups and can send to multiple multicast addresses.
How are IP addresses divided into multicast addresses?
Multicast Explained. 2.1 Multicast addresses. As you probably know, the range of IP addresses is divided into “classes” based on the high order bits of a 32 bits IP address: The one which concerns us is the “Class D Address”. Every IP datagram whose destination address starts with “1110” is an IP Multicast datagram.
How does a router listen for multicast messages?
A router will determine if any of the hosts on a locally attached network are configured to receive multicast datagrams using IGMP (Internet Group Management Protocol). Routers will listen for IGMP messages and periodically send queries on the local subnet. using the multicast group address 224.0.0.1 (Reserved All hosts address).
Can A Level 2 host send and receive multicast traffic?
Level 2 hosts must be able to both send and receive multicast traffic. They must know the way to join and leave multicast groups and to propagate this information to multicast routers. Thus, they must include an Internet Group Management Protocol (IGMP) implementation in their TCP/IP stack. 2.3 Sending Multicast Datagrams.