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610-0184-095 June 14, 2001
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.