Blog Post

IGMP (Internet Group Management Protocol) is a network layer protocol that is used to enable the communication between a multicast router and host which wants to receive the multicast group traffic. By default, using IGMP version-2. In this blog, cover the below-mentioned topics-

IGMP Version-1

IGMP Version-2

IGMP Version-3

IGMP version-3 will cover in my next blog.

IGMP Version-1

IGMP Version-1 is the first protocol that is by default not in use. In this version, IGMP uses only two types of messages, which are Report and Query messages. Find below-mentioned details about message types-

Message Types

There are two types of messages which are used in IGMP version-1

Report Message- A report message is sent by the host which are wanting to join the multicast stream.

Query Message- Query message is used by Multicast router which will send a query to check if any host wants to join the multicast stream or not. This is a periodic message to host on 224.0.0.1, which is by default using 60 seconds and, in this message, include MRT (Maximum Response Time 10 Sec) value. If no host wants to join the stream or after three times query message does not get any report message automatic stop to send the multicast traffic.

If one or some of the hosts send report messages and receive them by the multicast router it will start to flood on all LAN host ports which either want to join or not.

IGMP Version-2

IGMP version-2 is the better or enhanced version of IGMP version-1. Here is some additional message like leave message that is introduced which is highly effective to control the flooding the multicast traffic. By default, IGMP version-2 is used. In this version, we can modify the MRT (Max Response Time) value to 0-25 Sec and by default, time use 10 Second.

IGMP Version-2 Header information

Message Types- There are generally three types of messages used in IGMP version-2.

Member Report message- A report message is sent by a host which is wanting to join the multicast stream. This message is similar to the IGMP Version-1.

Query Message- Query message is to be sent by a router that is sent to any specific group. This message is used for if any router wants to receive the multicast traffic, they can send a report message for that group. Default query interval time is 60 seconds and hold time is 120 seconds.

Leave Report Group Message- Leave message only sent by the LAN connected host, if any host doesn’t want anymore the multicast traffic sent the leave message. When the multicast router gets the leave message on that particular group user connected port after that router stop to send the multicast traffic on the same but other hosts (who already receiving traffic) will be not any impact.

To sum up we can say that IGMP is used to establish communication between the host to a multicast router. But due to some of the advantages and enhancements, we use Version-2 and Version-3. As we know, there is no mechanism to control the multicast stream flooding on the version but after some enhancement to Version-2, one Leave message is introduced which is to control the multicast flooding. Reach out to us through email or you can also call us on +91 9773973971.

Author
Brijesh Yadav
Network Consultant Engineer