1. A tool for locating QoS failures on an Internet path
10th TF-NGN meeting, Rome, February 6th-7th 2003
TraceQoS
A tool for locating QoS failures on an Internet path
Chris Welti, Network Engineer, SWITCH

2. Outline Introduction What is TraceQoS? Demonstration Implementation
System requirements

3. Introduction
Use of Internet for transfer of real-time processed data (e.g. video streams)
Depend on certain QoS of underlying network (e.g. max. dv)
Difficult to locate end-2-end QoS performance problems in IP networks
Crossing management domains
Network operators claim their networks work flawlessly
No common tool for measuring one-way metrics segment by segment over an end-2-end path

4. What Is TraceQoS?
Active one-way measurement system for locating QoS „failures“ on an IP path from source to destination
On demand tests
TraceQoS measures OWD, OWDV, OWPL segment by segment over end-2-end path
Concurrent measurements on the subpaths
Dynamically displays results while test is in progress
-> Helps to locate segments on the investigated path where QoS performance is not sufficient

5. A Sample TraceQoS Scenario
LEGEND:
TS = TraceQoS server
rts = link from router to TS
tsr = link from TS to router
mp = measurement path

6. TraceQoS User Interface
TraceQoS client
Perl Script
User Parameters:
Destination host
Test port
Preferred address family (IPv4/IPv6)
Number of packets to send
Packet size
Packet rate

7. TraceQoS Result Viewer
Dynamic display of current test traffic while in progress (OWD, OWDV, packet loss)

8. TraceQoS Result Viewer (2)
Result visualisations of the test session (qosplot)
Can be displayed in a web-browser.

9. TraceQoS
LIVE DEMO

10. Implementation
TraceQoS servers connected to routers on the path to be investigated
TraceQoS client:
Traceroute to destination
Looks for matching TraceQoS servers along the path found
Sends test requests to the TraceQoS servers found
Polls packet traces from the TraceQoS servers involved
Generates statistics and displays them to the user

11. Control protocol Tests are initiated through HTTP (CGI)
Perl-scripts on TraceQoS servers to:
Start a sender test session
Start a receiver test session
Get current packet-trace
Stop a test session

12. TraceQoS operating sequence

13. TraceQoS Test Traffic C programs to generate and receive test traffic
Fixed size UDP packets
IPV4 or IPV6
Sent in poisson-distributed time intervals to avoid synchronization effects
Packets contain:
Test ID
Sequence number
Timestamp of sending
Padding data

14. Interesting Test Results
NTP time drift

15. Interesting Test Results (2)
Busy router CPU

16. System Requirements For The Prototype
TraceQoS server:
Well-connected Linux machine (lightly loaded, short & fast connection to router)
Clock synchronization (GPS or NTP) for OWD measurements
Must be able to accept & send packets at least on UDP port (test traffic) and TCP port 80 (HTTP, control protocol)
Software: Web Server with CGI (preferrebly Apache 1.3)
Perl 5 and some Perl-libraries (libwww, file-tail, etc.)

17. THE END Thank you for your attention!
For more information about TraceQoS contact me: