What is Internet Group Management Protocol (IGMP)?

Since the great success of streaming services such as Netflix and Spotify, IP multicasting has become an indispensable transmission method for the Internet. This technical procedure enables the sender to send data streams to entire receiver groups, enabling them to make optimum use of transport and routing capacities. Without this transmission method, the sender would have to send separate data packets to each receiving device, which would require enormous bandwidth and would quickly lead to an overload. This would make it practically impossible to keep the service permanently available. The Internet Group Management Protocol (IGMP) is a protocol that plays an important role in the organization of these multicast receiver groups in IPv4 networks.

What is Internet Group Management Protocol (IGMP)?

IGMP is an acronym for Internet Group Management Protocol. IGMP is a communication protocol used by hosts and adjacent routers for multicasting communication with IP networks and uses the resources efficiently to transmit the message/data packets. Multicast communication can have single or multiple senders and receivers and thus, IGMP can be used in streaming videos, gaming, or web conferencing tools. This protocol is used on IPv4 networks and for using this on IPv6, multicasting is managed by Multicast Listener Discovery (MLD).

Like other network protocols, IGMP is used on the network layer. MLDv1 is almost the same in functioning as IGMPv2 and MLDv2 is almost similar to IGMPv3. The communication protocol, IGMPv1 was developed in 1989 at Stanford University. IGMPv1 was updated to IGMPv2 in the year 1997 and again updated to IGMPv3 in the year 2002. The IGMP protocol is used by the hosts and router to identify the hosts in a LAN that are the members of a group. IGMP is a part of the IP layer and IGMP has a fixed-size message. The IGMP message is encapsulated within an IP datagram.

How does IGMP work?

Computers and other devices connected to a network use IGMP when they want to join a multicast group. A router that supports IGMP listens to IGMP transmissions from devices to figure out which devices belong to which multicast groups.

IGMP uses IP addresses that are set aside for multicasting. Multicast IP addresses are in the range between 224.0.0.0 and 239.255.255.255. (In contrast, anycast networks can use any regular IP address.) Each multicast group shares one of these IP addresses. When a router receives a series of packets directed at the shared IP address, it will duplicate those packets, sending copies to all members of the multicast group.

IGMP multicast groups can change at any time. A device can send an IGMP “join group” or “leave group” message at any point.

IGMP works directly on top of the Internet Protocol (IP). Each IGMP packet has both an IGMP header and an IP header. Just like ICMP, IGMP does not use a transport layer protocol such as TCP or UDP.

What types of IGMP messages are there?

The IGMP uses several types of messages to manage multicast group memberships:

• IGMP Membership Query: The Sent by routers to determine which multicast groups have members on a particular network segment. This query helps routers maintain accurate multicast group membership information.
• IGMP Membership Report: Sent by hosts to indicate their interest in joining a multicast group. This report informs the router of the presence of a host that wants to receive multicast traffic.
• IGMP Leave Group: Sent by hosts to indicate that they are leaving a multicast group. This message informs the router that the host no longer wants to receive traffic for that group.
• IGMP V3 Membership Report (in IGMPv3): This allows hosts to specify the exact multicast group addresses they want to join or leave and can include source-specific multicast (SSM) information.

Advantages of Internet Group Management Protocol

The main advantage of IGMP is its ability to conserve network resources by delivering multicast traffic only to those hosts that have expressed interest in receiving it. With IGMP, routers can maintain a table of active multicast groups and associated member hosts, allowing for efficient routing and delivery of multicast packets. This reduces network congestion and ensures that bandwidth is utilized optimally.

Additionally, IGMP provides a scalable solution for managing multicast group memberships. Hosts can dynamically join or leave multicast groups, allowing for flexibility in network configurations. This enables multicast applications to adapt to changing network conditions and ensures that multicast traffic is delivered to the intended recipients in a timely manner.

IGMP Types

The Internet Group Management Protocol (IGMP) is a communication protocol that manages the participation of hosts in multicast groups.

There are three types of IGMP: IGMP version 1, IGMP version 2, and IGMP version 3.

• IGMP version 1 was the first iteration of the protocol, and it allows a host to signal its interest in joining a particular multicast group.
• IGMP version 2 builds upon the functionality of version 1 by allowing hosts to indicate their desire to leave a multicast group.
• IGMP version 3 adds the ability for a host to report its current Multicast Listener state, providing more efficient group membership reporting.

When is the Internet Group Management Protocol used?

The role of IGMP is clearly defined: The communication protocol is always used where multicast transmissions are required in IPv4 networks such as the Internet. Classic deployment scenarios are real-time applications that run over multipoint connections – such as web conferencing tools or live streaming services. Not every client should have to be supplied with the required data stream individually, as this would quickly lead the output server and network nodes to overload.

Conclusion

IGMP is a critical protocol for networking. It allows devices on a network to communicate with one another and determine which multicast groups they should subscribe to.

By understanding how IGMP works, you can create smoother, more efficient networks that are better equipped to handle today’s high-bandwidth applications and media streaming services.