HP-UX IPQoS Performance and Sizing White Paper

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Abstract
This document outlines the performance impact of HP-UX IPQoS on an HP-UX system. It is divided into
five sections. The first section is an introduction to IPQoS; the second section is about the tool used for
the tests; the third section gives an overview of test configuration; the fourth section gives an
interpretation of the test results; the fifth section contains raw test result data in tabular form; and the
last section gives some suggestions for further study.
Introduction
During the past few years, the Internet has evolved from a simple network carrying primarily data
traffic, into a complex network handling a variety of traffic, ranging from real time audio and video to
web traffic. However, in terms of throughput, delay and packet loss, the “best effort” nature of the
current Internet is not sufficient to cope with the requirements of this type of traffic.
HP-UX IPQoS can be used to bring an HP-UX node into conformance with the IETF Differentiated
Services (DiffServ) model. The key features of HP-UX IPQoS are:
• Conforms to the IETF Differentiated Services (DiffServ) Model.
• Provides differentiated classes of service on outbound traffic by performing traffic
conditioning actions. Important traffic classes can take bandwidth away from less important
classes, up to user-specified limits.
- Classification occurs when traffic classes are defined in filters.
- Marking occurs when marking attributes are set in policies.
- Metering occurs when bandwidth is reserved for defined traffic classes
in policies.
• Allows DSCP and VLAN marking on outbound traffic from the HP-UX server.
- Can assign different DSCP network routing priorities (valid range 0-63).
- Can assigned different VLAN priorities (valid range 0-7).
• Supports traffic classification on broad range of packet attributes.
• Provides provisioned QoS management.
• Supports both IPv4 and IPv6.
HP-UX IPQoS performs the above items by reading the header of an IP packet (plus transport
TCP/UDP header) and comparing it to a set of user configured rules. The specific action is taken
based on the rules. Because HP-UX IPQoS only reads the IP header, the size of an IP packet does not
affect the speed at which HP-UX IPQoS processes the packet.
However, the faster an interface connection is, the more packets per second it can handle. A link
capable of 56 Kbps and 1.544Mbps can carry up to 350 and 9650 packets per second,
respectively. Faster connections such as 10-baseT (Ethernet) and 100-baseT (Fast Ethernet) can carry
up to 62,500 and 625,000 packets respectively.
Because HP-UX IPQoS works the same on all packets, regardless of size, the more packets an
interface can handle the more checking HP-UX IPQoS has to do. Therefore, the impact of HP-UX
IPQoS on a slower interface is minimal because there are not as many packets for it to check. The
performance impact of HP-UX IPQoS on a faster interface is greater, because more packets are
passing through, and HP-UX IPQoS must process them all.