* Apples to Apples: An Analysis of the Effects of mDNS Traffic: https://www.youtube.com/watch?v=miRV8qDOKBE
* How mDNS Can Kill Wi-Fi Performance And What To Do About It: https://www.youtube.com/watch?v=rd0dEwu4UJ4
It got me thinking about reducing airtime for broadcast traffic on Mikrotik, especially on larger networks bigger than a household with 100+ devices without the need to be draconian and disable any client to client comms and blocking most or all multicasts and broadcasts.
I don't have any real way to measure the actual time spent by the radio on handling broadcast transmissions so this is a bit of a thought experiment. Based on the talks I am testing the following on a Wifi/qcom-ac only network with cAPac's. Multicast enhance is enabled. These settings are running on each cAPac with 2 VLANs and SSIDs.
* Dropping all IPv6 mDNS. May or may not have consequences but it seems like redundant traffic for the most part.
* Sanitising the TTL and DSCP on IPv4 mDNS traffic.
* The usual priority mangle to make sure WMM works properly.
* As the bridge on qcom-ac is using VLAN filtering I have turned on IGMP snooping as well.
The AX devices don't use VLAN-Filtering for their CAPSMAN client interfaces normally (to date) so I haven't tested them.
Comments and suggestions welcome. I imagine there are a lot of other things that can be dropped too. The filtering should probably become more of a whitelist than a blacklist.
Code: Select all
/interface bridge settings
set use-ip-firewall=yes use-ip-firewall-for-vlan=yes
/interface bridge filter
add action=drop chain=forward comment="Drop all IPv6 mDNS" dst-mac-address=\
33:33:00:00:00:FB/FF:FF:FF:FF:FF:FF mac-protocol=ipv6
/ip firewall mangle
add action=change-ttl chain=forward comment="Sanitise mDNS TTL to 1" \
dst-address=224.0.0.251 dst-port=5353 log-prefix=ttl new-ttl=set:1 \
passthrough=yes protocol=udp src-port=5353 ttl=not-equal:1
add action=change-dscp chain=forward comment="Sanitise mDNS DSCP to 0" dscp=!0 \
dst-address=224.0.0.251 dst-port=5353 log-prefix=ttl new-dscp=0 \
passthrough=yes protocol=udp src-port=5353
/ip firewall mangle
add action=set-priority chain=postrouting comment="Set Prio outbound on Wifi" \
new-priority=from-dscp-high-3-bits out-bridge-port=all-wireless \
passthrough=yes