help …
I know it is possible to limit download and upload using a simple queue but what i was trying is that if i mark a limit say 512k download and 512k for upload then everything even youtube will also get 512k download and upload bandwidth. I want to make every connection to have 512k download and upload except youtube. can we make youtube to have 2mb bandwidth per user and other to have 256k speed.
Not very easily, no.
I have to say I don’t think I’ve ever seen anyone wanting to give YouTube MORE bandwidth than the standard per-user amount. 
If you really want to try - the best thing to do is to get a list of all of Google’s IP ranges (they have several, obviously) from some source - such as a BGP looking-glass site (like BGP.he.net) and make an IP address-list of these prefixes, and then do your youtube matching based on the address-lists.
That wouldn’t be totally clean though, because google drive, google hangout, any other google-hosted service would be subject to the 2M queue and not the 512K queue.
can i get your email address ? please
use layer7 protocol
^.+(youtube|googlevideo.com).*$
add action=add-dst-to-address-list address-list=youtube \
address-list-timeout=12h chain=forward layer7-protocol=youtube
then add packet mark mangle for address-list
then add queue for this packet mark
its my idea
layer7 protocol won’t match SSL-protected connections, which Youtube forces. It may catch some connections if the user is typing a specific URL for youtube and they’re not typing httpS:// at the beginning of their urls, but if they follow links, or click a “suggested video” - sooner or later they’re going to hit a CDN node immediately with SSL and it’s not going to be marked “youtube”
/ip firewall layer7-protocol
add name=youtubeBW regexp=^.+(youtube|googlevideo.com).*$
/ip firewall mangle
add action=mark-packet chain=forward comment=youtube layer7-protocol=\
youtubeBW new-packet-mark="youtube packet"
/queue type
add kind=pcq name=PCQ pcq-classifier=dst-address pcq-dst-address6-mask=64 \
pcq-rate=256k pcq-src-address6-mask=64
/queue simple
add limit-at=0/0 max-limit=256k/256k name=Youtube packet-marks=\
"youtube packet" queue=PCQ/PCQ target=""
This mangle rule won’t work. Modify it to mark CONNECTION (not packet) and add another rule to mark packet if CONNECTION mark = YouTube.