Product guide

Quality of Service (QoS): Managing Bandwidth More Effectively
Introduction
Classifiers for Prioritizing Outbound Packets
The classifiers used in the 3400cl/6400cl switches are a subset of the classifiers
used in the 5300xl and 4200vl switches. Also, the 3400cl/6400cl switches
search for classifier matches in the opposite order of that used in the 5300xl
and 4200vl switches.
Not e On Using
Mult ipl e
Cr iter i a
HP recommends that you configure a minimum number of the available QoS
classifiers for prioritizing any given packet type. Increasing the number of
active classifier options for a packet type increases the complexity of the
possible outcomes and consumes switch resources.
5300xl and 4200vl Packet Classifiers and Evaluation Order
The 5300xl and 4200vl switches provide seven QoS classifiers (packet criteria)
you can use to configure QoS priority.
Table 8-4. 5300xl and 4200vl Classifier Search Order and Precedence
Search
Order
Precedence QoS Classifier Type
1 1 (highest)
UDP/TCP Application Type (port)
2 2
Device Priority (destination or source IP address)
3 3
IP Type of Service (ToS) field (IP packets only)
4 4
Protocol Priority (IP, IPX, ARP, DEC LAT, AppleTalk, SNA, and NetBeui)
5 5
VLAN Priority
6 6
Incoming source-port on the switch
7 7 (lowest)
Incoming 802.1p Priority (present in tagged VLAN environments)
Where multiple classifier types are configured, a 5300xl or 4200vl switch uses
the highest-to-lowest search order shown in table 8-4 to identify the highest-
precedence classifier to apply to any given packet. When a match between a
packet and a classifier is found, the switch applies the QoS policy configured
for that classifier and the packet is handled accordingly.
Note that on a 5300xl or 4200vl switch, if the switch is configured with multiple
classifiers that address the same packet, the switch uses only the QoS config-
uration for the QoS classifier that has the highest precedence. (In this case,
the QoS configuration for another, lower-precedence classifier that may apply
is ignored.) For example, if QoS assigns high priority to packets belonging to
VLAN 100, but normal priority to all IP protocol packets, since protocol
priority (4) has precedence over VLAN priority (5), IP protocol packets on
VLAN 100 will be set to normal priority.
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