Classification of Traffic
You can classify traffic by:
■802.1p tag priority (default)
■Physical source port
■IP characteristics of the frame (source address, destination address, and so forth)
Frames are classified into eight priorities, or classes, ranging in number from 0 to 7. By default, the switch uses the priority from the 802.1p tag field, if present, to assign a priority to a frame.
You can alternately set each physical port with a priority that ranges from 0 to 7. The switch then replaces the default 802.1p tag priority with the port priority as the priority of the frame.
You can, as a third alternative, set classification to be performed by the IP characteristics of packets, instead of 802.1 tag priority or port priority. To classify frames by their IP characteristics, you set a rule in an access control list (ACL). The rule can set a priority for traffic with a specific IP source address or with a specific combination of IP source address, IP destination address, IP protocol, TCP source port, and TCP destination port.
The priority of a rule in an ACL takes precedence over all other priorities in Queue Classification and Servicing classification. Because of this precedence, the switch determines whether a rule in an ACL exists for an IP frame in the final stage of classification. If a rule does exist, the priority associated with the rule replaces the current priority of the frame.
The switch then forwards the frames to the appropriate priority queue based upon the priority that is assigned to the frames.
June 14, 2001 | 5 |