HP ProCurve 5300xl Series Management Manual page 285

Table 8-6. Precedence Criteria for QoS Classifiers
Precedence Criteria
1 UDP/TCP Takes precedence based on a layer 4 UDP or TCP application, with a user-specified application
If a packet does not meet the criteria for UDP/TCP priority, then precedence defaults to the Device Priority
classifier, below.
2 Device
Priority
(IP
Address)
If a packet does not meet the criteria for device priority, then precedence defaults to the IP Type of Service
(ToS) classifier, below.
3 IP Type-
of-
Service
(IP ToS)
If a packet does not meet the criteria for ToS priority, then precedence defaults as follows:
– 5300xl switches: To the Protocol classifier
– 3400cl/6400cl switches: To the VLAN classifier
— Continued —
In general, the precedence of QoS classifiers should be considered when
configuring QoS policies. For example, suppose that a system administrator
has used an 802.1p priority rule to assign a high priority for packets received
on VLAN 100, but has also used another 802.1p priority rule to assign a normal
priority for TCP port 80 packets received on the switch. Since TCP/UDP port
precedence supersedes VLAN precedence, all TCP port 80 packets on VLAN
100 will be set to normal priority. For a classifier precedence listing, see table
8-5, ''3400cl/6400cl Classifier Search Order and Precedence'', on page 8-10.
Overview
port number (for example, Telnet). Default state: Disabled
Takes precedence based on an inbound packet having a particular destination or source IP
address. QoS applies the following IP address limits:
– 5300xl Switches: Up to 256 IP addresses
– 3400cl/6400cl Switches: Up to 60 IP address
If a given packet has a destination IP address matching a QoS configuration, this packet takes
precedence over another packet that has the matching IP address as a source address. (This
can occur, for example, on an outbound port in a switch mesh environment.) Also, if the source
and destination IP addresses (SA and DA) in the same packet match for different QoS policies,
the DA takes precedence. Default state: No IP address prioritization.
Takes precedence based on the TOS field in IP packets. (Applies only to IP packets.) The ToS
field is configured by an upstream device or application before the packet enters the switch.
• IP Precedence Mode: QoS reads an inbound packet's IP precedence (upper three) bits in
the Type-of-Service (ToS) byte and automatically assigns an 802.1p priority to the packet (if
specified in the QoS configuration) for outbound transmission.
• Differentiated Services (Diffserve) Mode: QoS reads an inbound IP packet's differentiated
services, or codepoint (upper six), bits of the Type-of-Service (TOS) byte. Packet
prioritization depends on the configured priority for the codepoint. (Some codepoints default
to the DSCP standard, but can be overridden.)
For more on IP ToS, see "QoS IP Type-of-Service (ToS) Policy and Priority" on page 8-36. Default
state: Disabled.
Quality of Service (QoS): Managing Bandwidth More Effectively
Introduction
8-11