title: High precision timing in passive measurements of data networks

authors: Donnelly, Stephen F.

abstract: Understanding, predicting, and improving network behaviour under a wide range of conditions requires accurate models of protocols, network devices, and link properties. Accurate models of the component parts comprising complex networks allows the plausible simulation of networks in other configurations, or under different loads. These models must be constructed on a solid foundation of reliable and accurate data taken from measurements of relevant facets of actual network behaviour.
As network link speeds increase, it is argued that traditional network measurement techniques based primarily on software time-stamping and capture of packets will not scale to the required performance levels. Problems examined include the difficulty of gaining access to high speed network media to perform measurements, the insufficient resolution of time-stamping clocks for capturing fine detail in packet arrival times, the lack of synchronisation of clocks to global standards, the high and variable latency between packet arrival and time-stamping, and the occurrence of packet loss within the measurement system. A set of design requirements are developed to address these issues, especially in high-speed network measurement systems.
A group at the University of Waikato including myself has developed a series of hardware based passive network measurement systems called ‘Dags’. Dags use re-programmable hardware and embedded processors to provide globally synchronised, low latency, reliable time-stamping of all packet arrivals on high-speed network links with sub-hundred nanosecond resolution. Packet loss within the measurement system is minimised by providing sufficient bandwidth throughout for worst case loads and buffering to allow for contention over shared resources. Any occurrence of packet loss despite these measures is reported, allowing the invalidation of portions of the dataset if necessary. I was responsible for writing both the interactive monitor and network measurement code executed by the Dag’s embedded processor, developing a Linux device driver including the software part of the ‘DUCK’ clock synchronisation system, and other ancillary software.
It is shown that the accuracy and reliability of the Dag measurement system allows confidence that rare, unusual or unexpected features found in its measurements are genuine and do not simply reflect artifacts of the measurement equipment. With the use of a global clock reference such as the Global Positioning System, synchronised multi-point passive measurements can be made over large geographical distances. Both of these features are exploited to perform calibration measurements of RIPE NCC’s Test Traffic Measurement System for One-way-Delay over the Internet between New Zealand and the Netherlands. Accurate single point passive measurement is used to determine error distributions in Round Trip Times as measured by NLANR’s AMP project.
The high resolution afforded by the Dag measurement system also allows the examination of the forwarding behaviour of individual network devices such as routers and firewalls at fine time-scales. The effects of load, queueing parameters, and pauses in packet forwarding can be measured, along with the impact on the network traffic itself. This facility is demonstrated by instrumenting routing equipment and a firewall which provide Internet connectivity to the University of Auckland, providing passive measurements of forwarding delay through the equipment.both the interactive monitor and network measurement code executed by the Dag’s embedded processor, developing a Linux device driver including the software part of the ‘DUCK’ clock synchronisation system, and other ancillary software. It is shown that the accuracy and reliability of the Dag measurement system allows confidence that rare, unusual or unexpected features found in its measurements are genuine and do not simply reflect artifacts of the measurement equipment. With the use of a global clock reference such as the Global Positioning System, synchronised multi-point passive measurements can be made over large geographical distances. Both of these features are exploited to perform calibration measurements of RIPE NCC’s Test Traffic Measurement System for One-way-Delay over the Internet between New Zealand and the Netherlands. Accurate single point passive measurement is used to determine error distributions in Round Trip Times as measured by NLANR’s AMP project.
The high resolution afforded by the Dag measurement system also allows the examination of the forwarding behaviour of individual network devices such as routers and firewalls at fine time-scales. The effects of load, queueing parameters, and pauses in packet forwarding can be measured, along with the impact on the network traffic itself. This facility is demonstrated by instrumenting routing equipment and a firewall which provide Internet connectivity to the University of Auckland, providing passive measurements of forwarding delay through the equipment.

text: High precision timing in passive measurements of data networks Understanding, predicting, and improving network behaviour under a wide range of conditions requires accurate models of protocols, network devices, and link properties. Accurate models of the component parts comprising complex networks allows the plausible simulation of networks in other configurations, or under different loads. These models must be constructed on a solid foundation of reliable and accurate data taken from measurements of relevant facets of actual network behaviour.
As network link speeds increase, it is argued that traditional network measurement techniques based primarily on software time-stamping and capture of packets will not scale to the required performance levels. Problems examined include the difficulty of gaining access to high speed network media to perform measurements, the insufficient resolution of time-stamping clocks for capturing fine detail in packet arrival times, the lack of synchronisation of clocks to global standards, the high and variable latency between packet arrival and time-stamping, and the occurrence of packet loss within the measurement system. A set of design requirements are developed to address these issues, especially in high-speed network measurement systems.
A group at the University of Waikato including myself has developed a series of hardware based passive network measurement systems called ‘Dags’. Dags use re-programmable hardware and embedded processors to provide globally synchronised, low latency, reliable time-stamping of all packet arrivals on high-speed network links with sub-hundred nanosecond resolution. Packet loss within the measurement system is minimised by providing sufficient bandwidth throughout for worst case loads and buffering to allow for contention over shared resources. Any occurrence of packet loss despite these measures is reported, allowing the invalidation of portions of the dataset if necessary. I was responsible for writing both the interactive monitor and network measurement code executed by the Dag’s embedded processor, developing a Linux device driver including the software part of the ‘DUCK’ clock synchronisation system, and other ancillary software.
It is shown that the accuracy and reliability of the Dag measurement system allows confidence that rare, unusual or unexpected features found in its measurements are genuine and do not simply reflect artifacts of the measurement equipment. With the use of a global clock reference such as the Global Positioning System, synchronised multi-point passive measurements can be made over large geographical distances. Both of these features are exploited to perform calibration measurements of RIPE NCC’s Test Traffic Measurement System for One-way-Delay over the Internet between New Zealand and the Netherlands. Accurate single point passive measurement is used to determine error distributions in Round Trip Times as measured by NLANR’s AMP project.
The high resolution afforded by the Dag measurement system also allows the examination of the forwarding behaviour of individual network devices such as routers and firewalls at fine time-scales. The effects of load, queueing parameters, and pauses in packet forwarding can be measured, along with the impact on the network traffic itself. This facility is demonstrated by instrumenting routing equipment and a firewall which provide Internet connectivity to the University of Auckland, providing passive measurements of forwarding delay through the equipment.both the interactive monitor and network measurement code executed by the Dag’s embedded processor, developing a Linux device driver including the software part of the ‘DUCK’ clock synchronisation system, and other ancillary software. It is shown that the accuracy and reliability of the Dag measurement system allows confidence that rare, unusual or unexpected features found in its measurements are genuine and do not simply reflect artifacts of the measurement equipment. With the use of a global clock reference such as the Global Positioning System, synchronised multi-point passive measurements can be made over large geographical distances. Both of these features are exploited to perform calibration measurements of RIPE NCC’s Test Traffic Measurement System for One-way-Delay over the Internet between New Zealand and the Netherlands. Accurate single point passive measurement is used to determine error distributions in Round Trip Times as measured by NLANR’s AMP project.
The high resolution afforded by the Dag measurement system also allows the examination of the forwarding behaviour of individual network devices such as routers and firewalls at fine time-scales. The effects of load, queueing parameters, and pauses in packet forwarding can be measured, along with the impact on the network traffic itself. This facility is demonstrated by instrumenting routing equipment and a firewall which provide Internet connectivity to the University of Auckland, providing passive measurements of forwarding delay through the equipment.

year: 2002

title: Using shared displays to support group design; A study of the use of informal user interface designs when learning to program

authors: Plimmer, Beryl

abstract: Hand-drawn sketches have traditionally been used to depict design ideas because they are quick to draw and can include as much or little detail as is required to convey the essence of the ideas. Computer tools are now an alternative and offer advantages for editing, storing and transmitting designs. However, designers consistently reject using current computer tools because these tools interrupt the creative process. Various studies have supported the designer's position, consistently showing that traditional tools produce more and better design ideas. 

This thesis describes the development and evaluation of a design-friendly computer tool that focuses specifically on the needs of the novice programmer who is designing user interfaces. From an extensive review of the literature on design, learning to programming and previous sketch tools we extracted the specifications for a tool that: compares favourably as a design medium with traditional tools such as the pen, paper and whiteboards, provides the editing and storage support expected of computer tools, helps students to gain a better understanding of programming problems and integrates seamlessly into a program development environment.

Freeform, the tool we have developed to these specifications, has had two iterations of development and usability testing. This tool is unique in that it: is integrated into a commercial program development environment, uses a digital whiteboard for interaction and includes character recognition. Using Freeform, students can both quickly hand-draw user interface designs and interact with the design while it is still rendered as a sketch. When satisfied with the design the student invokes the recognition engine. The sketch is then overlaid with recognition data. Any incorrect interpretations can be altered by the student. The student can then instruct Freeform to create the formal user interface in the program development environment. The translation of sketch glyphs to user interface widgets is achieved by parsing the sketch and recognition data with transformation rules. 

We have conducted two evaluation studies using Freeform. The first study directly compared Freeform to a traditional alternative. We found that, although the design quality was similar, the students believed that when they were using Freeform they both understood the problem better and enjoyed the experience more. We noted during this study that the interactive checking available in Freeform prompted more changes to the designs than the static checking done on a standard whiteboard. In the second study, we asked students to check designs rendered as both sketches in Freeform and as formal diagrams in a user interface builder. The students made significantly more revisions to the Freeform sketches and therefore produced better designs from Freeform. 

The usability tests and evaluation studies we have conducted suggest that computer-based low-fidelity design tools: can compete favourably with traditional tools as a design medium, offer better support for editing and storage, and may have advantages for checking over both traditional sketch mediums and formal interactive computer designs.

text: Using shared displays to support group design; A study of the use of informal user interface designs when learning to program Hand-drawn sketches have traditionally been used to depict design ideas because they are quick to draw and can include as much or little detail as is required to convey the essence of the ideas. Computer tools are now an alternative and offer advantages for editing, storing and transmitting designs. However, designers consistently reject using current computer tools because these tools interrupt the creative process. Various studies have supported the designer's position, consistently showing that traditional tools produce more and better design ideas. 

This thesis describes the development and evaluation of a design-friendly computer tool that focuses specifically on the needs of the novice programmer who is designing user interfaces. From an extensive review of the literature on design, learning to programming and previous sketch tools we extracted the specifications for a tool that: compares favourably as a design medium with traditional tools such as the pen, paper and whiteboards, provides the editing and storage support expected of computer tools, helps students to gain a better understanding of programming problems and integrates seamlessly into a program development environment.

Freeform, the tool we have developed to these specifications, has had two iterations of development and usability testing. This tool is unique in that it: is integrated into a commercial program development environment, uses a digital whiteboard for interaction and includes character recognition. Using Freeform, students can both quickly hand-draw user interface designs and interact with the design while it is still rendered as a sketch. When satisfied with the design the student invokes the recognition engine. The sketch is then overlaid with recognition data. Any incorrect interpretations can be altered by the student. The student can then instruct Freeform to create the formal user interface in the program development environment. The translation of sketch glyphs to user interface widgets is achieved by parsing the sketch and recognition data with transformation rules. 

We have conducted two evaluation studies using Freeform. The first study directly compared Freeform to a traditional alternative. We found that, although the design quality was similar, the students believed that when they were using Freeform they both understood the problem better and enjoyed the experience more. We noted during this study that the interactive checking available in Freeform prompted more changes to the designs than the static checking done on a standard whiteboard. In the second study, we asked students to check designs rendered as both sketches in Freeform and as formal diagrams in a user interface builder. The students made significantly more revisions to the Freeform sketches and therefore produced better designs from Freeform. 

The usability tests and evaluation studies we have conducted suggest that computer-based low-fidelity design tools: can compete favourably with traditional tools as a design medium, offer better support for editing and storage, and may have advantages for checking over both traditional sketch mediums and formal interactive computer designs.

year: 2004

title: An evaluation of the effectiveness of social equity strategies for Maori students in the School of Science and Technology

authors: Rua, Mohi

subjects: Maori students

abstract: In 1991 the School of Science and Technology (SOSAT) at the University of Waikato
had a very low participation rate of Maori and students from other non-dominant
ethnic groups. This situation was serious enough to concerned the then Dean of the
School and strategies were developed to change this situation. Four major strategies
are used to encourage, support and retain Maori students to successfully pursue and
complete a degree in Science. They are: the Te Putahi o te Manawa programme - a
mentoring programme; a scholarship and grant writing strategy (in particular
assistance with Tuapapa Putaiao Maori Fellowships(TPMFs) administered by FRST);
school visits; and field trips with secondary schools in the Waikato region that have a
high proportion of Maori students. The Maori & Psychology Research Unit (MPRU) was contracted by Gary Bramley of
the Equity Office of the SOSAT to conduct this evaluation. Evaluative information was gathered through administering questionnaires,
completing key informant interviews, and completing focus group interviews. In this evaluation we sought to determine the effectiveness of the social equity
strategies for Maori students in the SOSAT at the University of Waikato.

text: An evaluation of the effectiveness of social equity strategies for Maori students in the School of Science and Technology In 1991 the School of Science and Technology (SOSAT) at the University of Waikato
had a very low participation rate of Maori and students from other non-dominant
ethnic groups. This situation was serious enough to concerned the then Dean of the
School and strategies were developed to change this situation. Four major strategies
are used to encourage, support and retain Maori students to successfully pursue and
complete a degree in Science. They are: the Te Putahi o te Manawa programme - a
mentoring programme; a scholarship and grant writing strategy (in particular
assistance with Tuapapa Putaiao Maori Fellowships(TPMFs) administered by FRST);
school visits; and field trips with secondary schools in the Waikato region that have a
high proportion of Maori students. The Maori & Psychology Research Unit (MPRU) was contracted by Gary Bramley of
the Equity Office of the SOSAT to conduct this evaluation. Evaluative information was gathered through administering questionnaires,
completing key informant interviews, and completing focus group interviews. In this evaluation we sought to determine the effectiveness of the social equity
strategies for Maori students in the SOSAT at the University of Waikato.

year: 1999-11-11