Multicast handling on cnPilot

cnPilot Enterprise APs support IGMP snooping and multicast to unicast conversion to improve multimedia streaming performance.

When Multicast-To-Unicast conversion is enabled on a WLAN, the Access Point will being snooping all IGMP messages from wireless clients. IGMP v1/v2/v3 versions are all supported, and if a client subscribes to multiple multicast streams, they are all learnt by the Access Point and tracked.

Now when streaming begins, the Access  Point will convert all these multicast packets into unicast packets directed towards each client that has subscribed to the stream.

There are several advantages of serving the packets as unicast:

  1. Increased Reliability : unlike multicast frames, unicast frames in Wi-Fi networks are acknowledged by the receiving client. If the client does not receive the frame, the AP will retransmit it. This ensures increased reliability in the data transfer, especially in noisy environments.
  2.  Improved Performance : although for multiple clients the AP would have now made copies of the packet, now that these packets are unicast they can be transmistted at higher data rates and also make use of benefits like aggregation.

Since there are packet copies involved, as the number of clients subscribing to the same stream gets higher, the performance benefits start to level off (especially as we reach 10s of clients).

In firmware version 3.9 this feature is available in the CLI (mc2uc) and in cnMaestro device overrides. GUI config support is being added in an upcoming release.

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A post was split to a new topic: IGMP on E430W