HP-UX IPQoS A.01.00 Administrator's Guide (October 2005)

Introduction
Overview
Chapter 1 21
Traffic Classification
Traffic classification filters packets in a traffic stream into distinct classes (groups) based on
the content of parts of the packet header. In the classification process, IP packets are matched
against selectors of each filter to determine if the packet belongs in that filter class. Traffic
classifiers separate and steer traffic classes to traffic conditioners for further processing.
Two types of classifiers are defined in the DiffServ model. The Behavior Aggregate (BA)
Classifier selects packets based on the DSCP only. The Multi-Field (MF) classifier selects
packets based on the values of a combination of header fields such as source address,
destination address, and transport port numbers. HP-UX IPQoS provides BA and MF
classification.
Traffic Conditioning
Traffic conditioning consists of one or more of the following actions:
Metering Metering is part of the flow control strategy. Flow control measures traffic
flow for a class, then releases packets onto the network at a specified rate.
The metering component ensures conformance to configured flow rates.
Metering measures the traffic stream against a traffic profile specified via
policies in HP-UX IPQoS. It tracks the transmission rate of traffic flows on a
per-class basis. It then compares the actual flow rate against configured
flow rates, and passes state information to other conditioning functions to
trigger a specific action for each packet.
With HP-UX IPQoS, you can reserve a percentage of the total available
bandwidth; you can also specify a maximum bandwidth. See “Policy
Attributes” on page 71 for more information.
Marking Marking marks packets with values that translate to forwarding behaviors.
Marking is the basis for potential differentiated treatment when the packet
reaches a resource that recognizes the marking, such as a DS-aware router.
Forwarding behavior determines the priority and drop precedence of traffic
about to be forwarded on the network. This can involve marking or
re-marking the DS field of an IP packet with a DS codepoint (DSCP) value.
It can also involve marking or re-marking the VLAN tag of an Ethernet
frame header with a Class of Service (CoS) priority value.
After a value is placed in the packet header, the packet forwarding behavior
is determined by the forwarding scheme used by DS-aware nodes in the
network. For example, different traffic classes can be steered to use
different routes such as reserved-traffic-only links and usage-based-billing
links. The steering depends on forwarding rules set in the DS-aware