Internet Control Message Protocol used by hosts & routers to • all the nodes using IP must have communicate network-level ICMP implemented information • ICMP msgs are only created for error reporting: the first IP fragment unreachable host, network, port, protocol warnings from routers or receivers network-layer above IP: ICMP msgs carried in IP datagrams
IGMP• IGMP is used by host receivers to join or leave a multicast host group.• IGMP is used by IPv4-based receivers.• The latest version at press time was Version 3. • IGMPv3 supports receivers that explicitly signal sources from which they wish to receive traffic.
IGMP OPERATION• IGMP is an asymmetric protocol.• Host Operations • To receive multicast datagrams, a host must join a group. To join a group, the host sends an IGMP membership report packet through an attached interface. 15
IGMP OPERATION• Multicast Router Operations • Multicast routers listen to all multicast addresses to detect membership reports. • 1. receiver (host) signals to join a group, • 2. creates an entry in the local group database. • 3. To verify group membership, multicast routers regularly send an IGMP Query message. 16