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Logicam QuickCam Express Web Camera Packet and Traffic Characteristics
CAIA Technical Report 040428A

Ana M. Pavlicic
Hwan-Yi Choo
April 28th, 2004

Introduction

This preliminary investigation of Logitech QuickCam Web Camera network traffic aims to report upon the inter-packet arrival times and packet size distributions of one and two way data rates. Traffic characteristics of web cameras are interesting to compare to previously collected data on Half-Life and Quake3 network games in identifying how such applications utilise network resources. The results of this investigation will form the basis for further research into the effect of jitter and latency on video interactions over the web.

Generating and Capturing Web Camera Traffic

Web camera traffic was captured in a LAN environment with one camera connected to each computer separated by a bridge computer running FreeBSD in order to collect the traffic flow. This paper looks at the traffic generated from Web Camera 1 on Computer 1 transmitting to Web Camera 2 on Computer 2 and both computers transmitting simultaneously. Each test was conducted over the period of one hour, although longer tests could be done with largely similar results.

Web Camera Computer Configurations

Computer Details
Computer
1 2
Brand
Dell Dell
Model
OPTIPLEX GX260 OPTIPLEX GX260
CPU
Pentium(R) 4 2.66GHz Pentium(R) 4 2.00GHz
RAM
256Mb 256Mb
OS
Microsoft Windows XP SP1 Microsoft Windows XP SP1
Web Camera
1 2


Equipment used for generating/capturing Web Camera traffic



Figure 1.1: Web Camera Equipment Setup


Computer 1 was connected via crossover cable directly to a bridge computer running FreeBSD. A 5-Port 10/100Mbps Nway Switch used to provide access to the Internet via the Swinburne University ITS network.

Each transmitting web camera resulted in two flows of traffic, the data packets and the ACK replies from the computer receiving the transmission. When simulteneous transmission from Web Camera 1 and Web Camera 2 occured, four flows of traffic were identified. In this report we refer to the data (and corresponding ACK replies) from Web Camera 1 to Computer 2 as Connection A and the data (and corresponding ACK replies) from Web Camera 2 to Computer 1 as Connection B. Figures 1.2 and 1.3 show a simlified network topology for Connection A and Connection B.



Figure 1.2: Connection A



Figure 1.3: Connection B


Bridge/Packet Sniffing Computer (136.186.299.64)
Unitron
CPU: Pentium 3 800MHz
RAM: 256Mb
OS: FreeBSD 4.9
Web Camera 1 and 2
Brand: Logitech
Model: QuickCam Express
Application: MSN Messenger Version 6.1
USB Port
Tcpdump was running on the Bridge/Packet Sniffing Computer and Pkthisto 0.3.3 was used to generate packet traffic histograms. Pkthisto recorded a traffic flow once it saw 50 packets and packets were required to arrive more frequently than 1000ms for the flow to be considered active. Each inter-packet arrival time and packet length histogram produced by Pkthisto represents a maximum of 500 packets.

Results/Discussion

The data set used for analysis was collected over a one day period. 1 hour sessions were observed, where one or two web cameras were used to transmit video data using MSN Messenger 6.1.

Single Idle Web Camera Traffic Results - Connection A time: 1hr 24sec
Single Active Web Camera Traffic Results - Connection A time: 1hr 10sec
Two Idle Web Camera Traffic Results - Connection A time: 1hr 22sec, Connection B time: 1hr 11sec
Two Active Web Camera Traffic Results - Connection A time: 1hr 39sec, Connection B time: 1hr 41sec

Summary and Further Analysis

The table below is a summary of the inter-packet arrival times and packet size distributions observed from the web camera network traffic.

 

Idle Web Camera Traffic
Active Web Camera Traffic
To Computer with Web Camera Transmitting
From Computer with Web Camera Transmitting
To Computer with Web Camera Transmitting
From Computer With Web Camera Transmitting
Inter-packet Arrival Times

3-9% at <0.25ms
67-79% at 201ms
10-18% at <0.25ms
46-57% at 201ms
11-14% at 201.25ms
15-27% at <0.25ms
60-65% between 35 and 100ms
49-54% at <0.25ms
4-11% at 2ms
27-35% between 35 and 100ms
Packet Lengths

89-<100% at 46 bytes
>0-11% at 52 bytes
3-5% at 64 bytes
11-20% at 1500 bytes
Other significant peaks at 856, 584, 1128 and between 924 and 1024 bytes

92-<100% at 46 bytes
>0-8% at 52 bytes

7-12% at 64 bytes
49-53% at 1500 bytes


As we can see form the table above, transmissions where there is no movement in front of the web camera result in inter-packet arrival times of 201ms between 46% or more packets. We can also see that a computer receiving a transmission sends mostly 46 byte ACK messages back to the computer sending the web camera transmission. The most common packet size sent by a computer transmitting video data is 1500 bytes.

When there is activity in front of the camera, there is a large percentage of packets with a 1usec to 249usec inter-packet arrival time (and 2ms inter-packet arrival time from the computer transmitting). There is also a significant percentage of packet sizes with inter-packet arrival times between 35 to 100ms. Again, the computer receiving a web camera transmission replies with mostly 46 byte ACK messages and the most common packet size sent by a computer transmitting data is 1500 bytes.

From the above statistical results, we can assume that when there is no movement in front of a web camera, packets are sent between the transmitting and receiving computers every 201ms. The receiving computer sends 46 byte ACK packets, while the transmitting computer sends a variety of packet sizes. When there is movement in front of the web camera a large percentage of packets arrive with an inter-arrival time of less than 0.25ms and between 35 and 100ms. Again, the computer receiving the web camera transmission generally only sends 46 byte ACK packets, while the transmitting computer sends a larger variety of packet sizes, most commonly 1500 byte packets.

Further research will include modelling web camera traffic in order to make statistical comparisons to models created by game traffic. It will aid in the development of software that uses packet statistics to identify and differentiate between applications producing traffic across a network.

Acknowledgements

Grenville Armitage, Director of Centre for Advanced Internet Architectures.





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Maintained by: Ana Pavlicic apavlicic@groupwise.swin.edu.au
Authorised by: Grenville Armitage garmitage@swin.edu.au

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