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What is IGMP?
2024-01-18 08:26:59

What is IGMP?

IGMP is an acronym that stands for "Internet Group Management Protocol". In IPv4 networks, hosts and nearby routers utilize the Internet Group Administration channel as a communications channel to create multicast group memberships. IP multicast relies on IGMP, which enables the network to send multicast broadcasts only to locations that have asked for them.

Applications enabling one-to-many networking, including online gaming and video streaming, can benefit from the adoption of IGMP, which makes resource usage more effective.

IPv4 networks employ the IGMP protocol. Unlike IGMP's plain IP encapsulation, Multicast Listener Discovery (MLD), a component of ICMPv6, handles multicast governance on IPv6 networks.

Buildings

IGMP functions between a server and a local multiplex router. These IGMP transactions provide useful information that is also obtained by switches that have IGMP snooping enabled. Then, to route multicast communication from hosts generating transmits to hosts that have registered over IGMP to receive them, Protocol Independent Multiplex (PIM) is utilized between the local and distant multicast routers.

Similar to other protocol families like ICMP, IGMP functions on the network's communication layer (layer 3).

The IGMP mechanism is used by routers and hosts alike. Through its local router, a host asks for group membership; meanwhile, a router watches for these kinds of inquiries and periodically broadcasts subscription questions. This querying function is chosen to be carried out by one firewall per subnet.

In the event that there isn't an IGMP-capable firewall in a level 2 network, certain multilayer switches can query IP addresses.

Iterations

IGMP is available in three versions. In 1989, IGMPv1 was defined. IGMPv2, which was introduced in 1997, enhances IGMPv1 by enabling a host to indicate their intention to exit a multicast group. By enabling source-specific multicast and introducing membership report aggregation in 2002, IGMPv3 enhanced IGMPv2. In 2006, source-specific multicast received better support.

The three IGMP versions are compatible with one another. Clients using IGMPv1, IGMPv2, and IGMPv3 can all be supported by a router that supports IGMPv3. IGMPv1 uses a query-response model. The address for queries is 224.0.0.1. The multicast address of the group receives membership reports. IGMPv2 modifies other timeouts and expedites the process of exiting a group. Messages for the leave group are routed to 224.0.0.2. A question unique to the group is presented. The multicast address of the group receives group-specific inquiries. We added a way for routers to choose an IGMP, which is querier for the network. IGMPv3 introduces source-specific multicast capability. Reports on membership are delivered to 224.0.0.22.

The necessary responsiveness of responses to a Member Query is indicated by the Max Resp Time (0x11). This parameter is set to 0 in other messages and is disregarded by the recipient; it only has any significance in Membership Queries. The field indicates time in fractions of a second; for example, a field that has a value of 10 indicates one second. When the final host departs a group, larger values lessen burstiness in IGMP traffic, while smaller values enhance protocol responsiveness.

Address Group

Submitting a Group-Specific and Group-and-Source-Specific Query queries this multicast address. When a General Query is sent, the field is zeroed.

The network layer offers a way to send and receive variable-length network packets over one or more networks from an origin to a destination host. The network layer replies to service responses from the layer of transportation and sends service responses to the content link layer in accordance with the service-level layering semantics imposed by the OSI (Open Services Interface) network architecture.

Link to the TCP/IP Architecture

The Internet's protocols are described under the TCP/IP paradigm. Above the connection layer in the TCP/IP paradigm is a layer known as the Internet layer. The OSI network layer and the TCP/IP Internet interface are often used interchangeably in books along with other secondary sources of information. This comparison, however, is deceptive since the two models' permissible attributes for protocols such as whether or not they are connection-based or connection-less that are inserted into these levels differ. In actuality, the network layer's capabilities are only partially represented by the TCP/IP Internet layer. The Internet is the only kind of network design that is covered.

Internet Protocol Packet Fragmentation

For IPv4 packets bigger than the lowest MTU of all the intermediary connections on the packet's transit to its destination, the network layer is in charge of fragmentation and reassembly. When necessary, routers can split up packets, and hosts can put them back together once they've been received.

On the other hand, packets sent over IPv6 are not broken up during forwarding; yet, in order to prevent packet loss, it is still necessary to determine the MTU that a particular route supports. This is accomplished by using Path MTU discovery between endpoints, which belongs in the Transport layer rather than this layer.

Multicast without Regard to Protocol

A family of multicast routing techniques for IP (Internet Protocol) networks known as Protocol-Independent Multicast (PIM) allows data to be distributed many-to-many and one-to-many via LANs, WANs, and the Internet. Because PIM uses routing data from other routing protocols rather than including its topological discovery technique, it is known as protocol-independent. PIM may utilize any unicast route protocol that is available on the network; it is not restricted to any particular one. PIM cannot create routing tables on its own. PIM forwards reverse paths using the unicast routing table.

Four Varieties of PIM

In PIM Sparse Mode (PIM-SM), shortest-path trees per resource are optionally created in addition to expressly building bidirectional shared trees grounded at a meeting point (RP) per group. PIM-SM scales rather well for wide-area use in general.

Routing with dense multicast is used in PIM Dense Mode (PIM-DM). By flooding the multicast traffic domain widely and then trimming back the portions of the tree where no recipients are present, it implicitly constructs shortest-path trees. Although it is simple to build, PIM-DM often has subpar scalability characteristics. Dense-mode multicast routing was utilized by DVMRP, which developed multicast routing technology. Refer to RFC 3973.

Bidire-PIM, or bidirectional PIM, constructs shared bi-directional trees directly. It may have higher end-to-end latency than PIM-SM since it never creates a path that is the shortest tree, but it scales well due to the fact that it doesn't require a source-specific state.70-73 Refer to RFC 5015.

For a restricted set of applications, PIM Source-Specific Broadcast (PIM-SSM) creates trees with a single source of rooting, providing a more scalable and safe paradigm (primarily content broadcasting). Receivers can receive an IP datagram in SSM by listening to the channel (S, G). An IP datagram is delivered by another source S to an SSM address that is the destination G. Refer to RFC 3569 for further details.

Mode Sparse

IP packets may be efficiently routed to multicast groups over wide-area and inter-domain online communities using the Protocol Independent Multimedia - Sparse-Mode (PIM-SM) protocol. The protocol is called sparse-mode because it is appropriate for groups where a relatively small fraction of the stations (and their routers) will be subscribed to the multicast session and protocol-independent because it does not rely on any specific unicast routing protocol to be used for topology discovery.

PIM-SM directly builds a tree from each writer to the readers in the multicast group, in contrast to previous dense-mode multichannel routing protocols like DVMRP and dense multichannel routing, which blasted packets throughout the network and then clipped off branches wherever there were no receivers.

Multicast Users

Explicit Join/Prune messages are sent to a router by neighbouring routers that have members in the downstream group. A host uses the Internet Group Monitoring Protocol (IGMP) to transmit its membership information to a multicast group, G, in order to join.

Data packets destined to a simulcast group G are subsequently sent by the router to just those interfaces that have received explicit join requests. For every group that has active members, a Designated Router (DR) periodically transmits Join/Prune messages towards a Rendezvous Point (RP) that is particular to that group.

It should be noted that all routers must formally connect through the meeting point (RP), which will be one router that is either statically or automatically identified as such. Every router en route to the RP creates a conditional (any-source) condition for the group in question and proceeds to transmit Join/Prune signals in that direction.

The state kept in a router to reflect the distribution tree is referred to as a route entry. Fields like the source address, group address, accepting interface for incoming packets, list of leaving interfaces for packets transmitted, timings, flag bits, etc., may all be found in a route entry. The incoming interface of the wild cards routes entry points to the RP.

The outgoing interfaces link to the immediately connected hosts that have applied to join group G, as well as the downstream neighbors that have issued Join/Prune messages to the RP. All group members are reached via the shared, RP-centered distribution tree created by this state.

Dense Mode

Dense Mode operates under the fundamental premise that there are receivers for the multiplexed packet stream in the majority of places. Relatively fewer receivers are assumed in sparse Mode. Dense Mode is best suited for groups (high-density groups) in which a large number of nodes subscribe to receive multicast packets, requiring the majority of routers to receive and send these packets.

The two methods' early behaviours and working processes demonstrate this distinction. Dense Mode handles IP multicast routing using a very straightforward method. At first, the source broadcasts to all routers that are immediately linked to it.