Side_1_360

described by the framework of GenSyn. This

includes models of web and FTP clients that

generate TCP traffic by downloading pages and

files from actual web servers, and models that

generate UDP traffic from a video server (using

MPEG), from voice over IP (VoIP), and in a

Constant Bit Rate (CBR) stream.

Besides generating traffic, there is a need for

accurate traffic measurements in order to derive

performance measures like unidirectional end-

to-end packet loss and delay. This has been

achieved by deploying PCs dedicated to traffic

monitoring using specialized hardware, so-called

DAG PCI cards. Section 3.1 describes the Gen-

Syn measurement platform developed for QoS

testing of IP networks.

A test scenario defines the application and proto-

col mixture, load level, traffic matrix and net-

work configuration (DiffServ, Best Effort, etc.).

Several test scenarios have been defined for test-

ing of the QoS mechanisms in an IP network.

The design of GenSyn test scenarios is presented

in Section 3.3 and examples of results that can

be obtained from such an experiment are found

in Section 3.4.

3.1 An Overview of the Measurement

Platform

The GenSyn traffic generator is used in dis-

tributed experiments with traffic generators run-

ning on several dedicated machines in the net-

work being tested. Because GenSyn is imple-

mented in Java, very little measurement func-

tionality is included on a per IP packet basis.

Instead, the measurement platform is based on

dedicated monitors, counters at the interface

cards (to monitor the routing and load balance),

and specialized equipment for generation and

analyzation like Smartbits.

Figure 15 shows the GenSyn test topology used

for QoS testing of an experimental IP network.

The figure illustrates all major components

including both GenSyn machines and dedicated

monitoring machines. The GenSyn PCs execute

Figure 15 GenSyn experiment
platform for IP networks

Internet

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User behaviour model

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User behaviour model

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User behaviour model

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Post-processing

PC

Generator

PC

Generator

PC

Monitoring

PC

Generator

PC

Generator

PC

Switch

Switch

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User behaviour model

Switch

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User behaviour model

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User behaviour model

Switch

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User behaviour model

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User behaviour model

File

server