This is a short reference for how to control bandwidth for different IP blocks.
Here,
192.168.1.0/24 is given 2mbps and
192.168.2.0/24 is given 4mbps bandwidth
I have set the Youtube IPs as Local, alternatively you can use Layer-7 for Youtube streaming.
/ip firewall mangle
add action=mark-connection chain=prerouting dst-address-list=Local new-connection-mark=youtube_2mbps passthrough=no src-address=192.168.1.0/24
add action=mark-packet chain=postrouting connection-mark=youtube_2mbps new-packet-mark=youtube_2mbps passthrough=no
add action=mark-connection chain=prerouting dst-address-list=Local new-connection-mark=youtube_4mbps passthrough=no src-address=192.168.2.0/24
add action=mark-packet chain=postrouting connection-mark=youtube_4mbps new-packet-mark=youtube_4mbps passthrough=no
/queue type
add kind=pcq name=youtube_2mbps pcq-classifier=dst-address pcq-dst-address6-mask=64 pcq-rate=2M pcq-src-address6-mask=64
add kind=pcq name=youtube_4mbps pcq-classifier=dst-address pcq-dst-address6-mask=64 pcq-rate=4M pcq-src-address6-mask=64
/queue tree
add name=youtube_2mbps packet-mark=youtube_2mbps parent=global-out queue=youtube_2mbps
add name=youtube_4mbps packet-mark=youtube_4mbps parent=global-out queue=youtube_4mbps
