In the following explains the concept of how Quality of Service functions with eight queues. Routers should fundamentally be able to prioritize packets according to the DSCP value in the IP header. A total of eight queues are available for this purpose, which are strictly prioritized. This means that packets are sent starting with the queue with the highest priority and working through to the queue with the lowest priority. A packet is assigned to a queue based either on the DSCP value in the IP header or by a firewall rule. Of the eight available queues two are reserved, one for the Urgent-Queue (highest priority, for internal services such as VCM and protocol packets) and the other for the Best-Effort-Queue (lowest priority, for all non-priority packets). The remaining six queues are freely available to the user. The priority levels of the individual queues are set by placing them in a Queue-List in descending order of priority. The internal Urgent-Queue and Best-Effort-Queue are inserted at the front and end of this Queue-List. The completed queue list must then be assigned to a physical WAN interface. Following this, any packets sent to this WAN interface are prioritized according to the configuration of the queues.
For QoS to work, the bandwidths or rates of an interface must be known in order for QoS to correctly distribute the load, e.g. in the case where bandwidths are allocated as a percentage. The bandwidths are usually taken from the upstream and downstream data rates from the internal DSL modems or from the bandwidth transmitted in the PPP by the provider.
For WAN connections via external modems or pure Ethernet connections, the actual bandwidths for the corresponding interfaces must be specified in the table under Downstream rate and Upstream rate.
Please note that the LCOS automatically sorts certain packets into the urgent queue. These include important negotiation packets such as IKEv2, BGP, or keepalive packets.
Forwarded TCP SYN and ACK packets are given preferential treatment and also sorted into the urgent queue. This behavior can be configured under .
These queues are configured in LANconfig under .
