The difference between IGMP snooping and proxy

Take a look at the diagram below, L2 switch turns on IGMP snooping,router1 is a remote multicast router that forwards multicast packets with the PIM protocol.

PIM, Protocol-Independent Multicast is a family of multicast routing protocols that can provide one-to-many and many-to-many distribution of data over the Internet. The "protocol-independent" part refers to the fact that PIM does not include its own topology discovery mechanism, but instead uses routing information supplied by other traditional routing protocols such as Border Gateway Protocol (BGP).
The role of enabling IGMP snooping is to listen to the IGMP report, query, and leave information between the IGMP router and the IGMP client. In this process, for the IGMP report, it will record the GDA (group destination address) in the MAC filter database of the switch.mac address is associated with which port. For leave message (IGMP v2), when the switch receives the leave message from the client, the switch will send a group query to see if there are no PCs in this group. If there is no reply, the entry will be deleted. For the case that IGMPV1 does not have a leave message, the IGMP router will periodically issue 224.0.0.1 queries, and the switch will send to the associated port according to the database. If it does not return for 3 consecutive times, the entry will be deleted.

What are the benefits of IGMP snooping?
 1. For a switch that does not support IGMP snooping, it will flood to each port after receiving a multicast packet, because its MAC address is GDA (01: 00: 5E: XX: XX: XX), there is no such entry in the switch, which can save bandwidth.
 2, for paid programs can control access.
 Let's take a look at the IGMP proxy. The topo is the same as above, except that the IGMP proxy is enabled on the layer2 switch.
Proxy, which means proxy, is similar to the http proxy, arp proxy process.

The IGMP router builds a multicast table by intercepting IGMP messages.Its function is divided into two parts.
The uplink port performs the host role, and the downlink port performs the router role.
The uplink port performs the role of a host and responds to queries from the router. When a new user group or the last user of a group exits, it actively sends a member report packet or leaves the packet.
The downlink port performs the role of a router, and it fully implements the mechanism specified in IGMP, including the querier election mechanism, periodically sending general query information, and sending specific queries when receiving leave packets.
The implementation mechanism of IGMP snooping is: The switch forms the correspondence between group members and switch interfaces by listening to the host reporting messages to the router's IGMP members; the switch forwards the received multicast data packets to the group members only according to the correspondence. Interface. IGMP Proxy and IGMP Snooping implement the same functions but have different mechanisms:
IGMP Snooping only obtains relevant information by listening to IGMP messages, while IGMP Proxy intercepts and processes the IGMP request of the end user, and then forwards it to the upper-layer router. Therefore, the table formed in IGMP snooping is the correspondence between group members and switch interfaces, and the multicast routing table is formed in IGMP Proxy. Equivalent to IGMP snooping, a layer 2 network device that implements IGMP proxy, assumes the role of Server on the user side, queries user information regularly, and assumes the role of Client on the network routing side, and sends the current user information to it when needed Network. Not only can achieve the purpose of suppressing the flood of Layer 2 multicast, but also can effectively acquire and control user information, and at the same time play a role in reducing network-side protocol messages to reduce network load.