See also other Mikrotik pages in this wiki

Background: http://www.rhyshaden.com/qos.htm

Snom Wiki: http://wiki.snom.com/Category:HowTo:QoS

Service Provider: http://wiki.mikrotik.com/wiki/Traffic_Priortization,_RouterOS_QoS_Implemetation

Enterprise QoS – A consistent QoS strategy: http://ethancbanks.com/2013/09/16/enterprise-qos-part-00-series-introduction/

http://gregsowell.com/?p=4665

These are notes on traffic prioritization with Mikrotik routers.

There is layer 2 and layer 3 QoS.

Layer 2 is in practice VLANs, where you give the packets in that VLAN a higher priority than packets in the default VLAN. The Ethernet switch is here the device that you need to control. If you do it right, you can have an ISDN-like quality level in your LAN, even if there is very heavy traffic in the LAN. You can set that up manually, but better is to use LLDP which is a kind of DHCP for the VLAN.

Layer 3 is using some bits in the IP header to tell the router with what priority the packet needs to be routed. The point here is that you need to have the router under your control. Those QoS bits are practically never used when you send a packet over the public Internet. But you can use then for example if you have a large corporate network where you control the routers.

From the PBX perspective, the PBX stays out of the discussion. You need to make sure that the PBX has an interface that has the VLAN set up correctly. The PBX tags (like the phones) the packets with reasonable bits on layer 3, so that the subsequent routers can process the packet accordingly.