Cisco QoS Cookbook for LAN
The Wiki of Unify contains information on clients and devices, communications systems and unified communications. - Unify GmbH & Co. KG is a Trademark Licensee of Siemens AG.
Cisco provides an abundance of documentation about Quality of Service, see below. This Wiki intends to boil down the information to a quick and simple LAN switch configuration guide, that works in most customer environments.
- Check the used CoS and DSCP values of the products used. Most Siemens products will use the DSCP values
- AF31 (i.e decimal value 26, binary 011010) for voice signaling and
- EF (i.e decimal value 46, binary 101110) for voice streams,
If in doubt, configure the phones/gateway/media server etc. to use those values.
- Turn on auto-qos on Cisco LAN switches and routers. This will turn on QoS in Cisco's switches and routers and will configure it with values, that match most customer's LAN environments. E.g. CoS=5 and DSCP=EF will be sent to the priority queue, if the router/switch is capable of doing so. Packets found in the priority queue are sent before any other packets are sent and therefore are used for real-time traffic.
- Define Trust boundaries: you need to talk to your customer on whether it is acceptable for him to trust its employees about the proper usage of packet priority markings.
- If the customer trusts on proper use of packet markings, and the access switches support this, configure mls qos trust dscp on access ports. Else configure mls qos trust cos.
- If the customer needs to control the proper usage of packet markings, the LAN switch needs to classify the packets based on other means. For Cisco routers, the most secure and convenient way is to use Cisco NBAR for classification at the network edges.
