La manera mas efectiva de marcar el trafico de video youtube en tu red (en este caso mikrotik) es utilizando listas de direcciones. Las recolecte por DNS y Whois.
Si queres hacer QoS, vas a necesitar esta lista.
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/ip fire addr
add address=173.194.0.0/16 disabled=no list=Youtube
add address=208.65.152.0/22 disabled=no list=Youtube
add address=64.15.112.0/20 disabled=no list=Youtube
add address=74.125.96.0/19 disabled=no list=Youtube
add address=72.14.221.0/24 disabled=no list=Youtube
add address=84.53.128.0/18 disabled=no list=Youtube
add address=87.248.192.0/19 disabled=no list=Youtube
add address=216.155.128.0/19 disabled=no list=Youtube
add address=208.73.208.0/21 disabled=no list=Youtube
add address=66.55.140.0/23 disabled=no list=Youtube
add address=74.125.208.0/24 disabled=no list=Youtube
add address=208.117.224.0/19 disabled=no list=Youtube

Buena suerte!!

Nicolas tech-nico.com