MVLAN-based IGMP modes include IGMP proxy and IGMP snooping.
IGMP Proxy
IGMP proxy is a mode in which the device in a tree topology does not set up a route to forward multicast messages, but only acts as a proxy for multicast protocol messages. Details are as follows:
From the perspective of a terminal, the device serves as a multicast router that implements the functions of the router in the IGMP protocol. Specifically, the device consistently functions as an IGMP querier (not supporting querier election for security concerns) on the user-side network. The device receives and terminates the join and leave messages of all multicast users, and duplicates the multicast program to only the interested multicast users according to the maintained group membership table.
From the perspective of a multicast router, the device serves as a multicast group member that implements the functions of the host in the IGMP protocol. According to the changes (addition or deletion) of the record in the group membership table, the device sends the join message or leave message of a program to the upper layer through the multicast uplink port. In addition, the device responds to the queries of the multicast router according to the status of the group membership table.
IGMP proxy effectively reduces the quantity of IGMP messages exchanged on the network side and therefore lessens the load of multicast routers. It is configurable on the device whether to send the IGMP general query to all multicast users or to only interested multicast users.
NOTE:
After a multicast user orders a program for the first time, the system generates a value, indicating the random interval. The value ranges from 0 to the difference between the interval for the general query and maximum response time to the general query. After the random interval, the system sends the first general query message to the multicast user.
IGMP Snooping
IGMP snooping enables the device to listen to the multicast protocol packets transmitted between the router and hosts and set up a Layer 2 forwarding table for multicast data packets. This manages and controls multicast data packet forwarding so that the multicast data packets can be sent only to specified recipients. IGMP snooping features:
· Low bandwidth requirements, facilitating separate host charging.
· Separate data forwarding for each VLAN, improving data security.
IGMP snooping has two types:
IGMP transparent snooping
It is a snooping function without proxy. The device selects the proxy, snooping, or snooping with proxy function based on MVLANs.
Before enabling IGMP transparent snooping, run the igmp query-proxy, igmp report-proxy, and igmp leave-proxy commands to disable proxy for query, report, and leave packets, respectively.
IGMP transparent snooping enables the device to process IGMP messages as follows:
Query message
After receiving the general query message and group-specific query message from the multicast uplink port, the device forwards the network-side query message to the user.
NOTE:
To ensure that the multicast user responds to the query in a timely manner, the maximum response time configured on the device must be shorter than that configured on the upper-layer multicast router.
The network-side IGMP version of the device is not affected by the multicast router.
Join/Leave message
The device transparently transmits all the join/leave message received from the multicast user to the MVLAN.
NOTE: The IGMPv3 message may contain multiple group records that match different MVLANs. In this case, the device segments the message and transparent transmits the segmented messages to the corresponding MVLANs.
IGMP snooping with proxy
In IGMP upstream transmission, IGMP snooping with proxy is the same as IGMP proxy; in IGMP downstream transmission, however, IGMP snooping with proxy does not suppress the query message as IGMP proxy does.
IGMP snooping with proxy enables the device to process IGMP messages as follows:
Query message
After receiving the query message from the multicast uplink port, the device reconstructs and sends the query message to the user (default mode, query proxy enabled based on MVLANs) or forwards the query message (disabling query proxy based on MVLANs). It also responds to the multicast router's query according to its multicast group membership table.
NOTE:
Like IGMP proxy, the network-side IGMP version of the device is affected by the multicast router.
Determine whether to enable query proxy. For details, see the "Usage Guidelines" of the igmp query-proxy command.
Join/Leave message
The device sends only the first join message from the multicast users to the MVLAN. The device sends only the last leave message from the multicast users to the MVLAN.
More blog:
No comments:
Post a Comment