LYU9802 Quality of Service in Wired/Wireless Communication Networks: Techniques and Evaluation Supervisor: Dr. Michael R. Lyu Marker: Dr. W.K. Kan Wan Yung Chun and Lam Shu Yin

Overview §Objectives §Introduction to Quality of Service (QoS) §QoS Parameters §Performance Evaluation l About Generic QoS l Ethernet and wireless LAN environment l Interconnected network with RSVP router §Future Works

Objectives §Provides a complete QoS solution in network l Network level (ATM, RSVP router) l System level (GQoS, our QoS scheme) l Application level (COBRA, building QoS application) §From this project, we can learn: l How to evaluate the performance of a system l How to design a good scheme l System programming experiences l Distributed programming in COBRA

QoS Definitions §The collective effect of service performances which determine the degree of satisfaction of a user. §The guarantee a network makes to an application in terms of providing a certain contracted level of service through out the application session. §Represents quantities,e.g. transfer rate, how long does the receiver have to wait for complete transmission, error rate, lost rate.

Importance of QoS §Growth of real-time network application is fast. §Growth of bandwidth cannot catch up the needs. §Simply expanding bandwidth is not effective. §Solution: Good management of bandwidth.

Problem of old management of bandwidth §TCP guarantees reliability and sequence §TCP uses reactive congestion control §IP offers only a best-effort model of service §No guarantees can be made to Real-Time and Multimedia Traffic

Current support of QoS §Application Level - IP Navigator l Commercial product, enhancing current IP protocol provides QoS network management. §System Level - Windows 98 l Provides Generic QoS §Network Protocol Level - IPv6 l Flow label (20 bits) and priority field (8 bits), instead of 4 class of TOS settings (8 bits). §Medium Access Sublayer Level - ATM l ATM supports QoS data transfer

Use of QoS §Mobile communication §Real-time video and sound transmission §Interactive applications on network §Routing for traffic with performance guarantees §QoS-aware ATM application

QoS Parameters §What is its function? l An adequate measure for the service quality provided by a network §QoS Mapping l Perceptual QoS l Application QoS l Network QoS

QoS Mapping

Network QoS Specification QoS Specifications Metrics Policies Security Performance Relative Management Levels of ImportanceServices Timeliness Precision Accuracy Combinations Latency Jitter Burst Tolerance Amount of data transmitted Reliability Connection failure probability Throughput Peak bandwidth Best effort Guaranteed Controlled load Confidentiality Integrity

Performance Evaluation of Generic Quality of Service in Microsoft Windows 98 ® §What is GQOS? l Microsoft's implementation of Quality of Service (QOS) §Levels of Service (LoS) l Best effort l Guaranteed l Controlled load

Why we choose GQoS? §Powered by Microsoft, it will soon be accepted as an industrial standard for QoS §GQoS is flexible and can run on any network environment, including wireless network §It lies on ReSerVation Protocol, which many network products begin to support it

Evaluation of GQoS Methodology of the experiment: ProgramQOSEVENT SourceSample program from Microsoft with our enhancement VersionMay 1998 EnvironmentEthernet and Wireless network Types of experiments: One sender and one receiver Two senders and one receiver

One sender and one receiver QoS disabled transmission takes the longest time. Guaranteed transmission remains stable all over the transmission. Best effort always takes the shortest time to complete.

Two senders and one receiver QoS disabled transmission always have a greater variation in transmission time.

Others §Three senders and one receiver experiment was done and similar result was obtained. §Other finding, l Importance of factors affecting the transmission time: This is due to the slow start feature of TCP congestion control. Whether the transmission is the current activated job in Windows. First to occupy the channel > Activation factor > Use of QoS

Wireless LAN §Network Configuration: Notebook computer  Wireless LAN  Proxim access point (base station)  Ethernet  Desktop computer

Experiment Measures §The Ethernet is connected to the access point and the desktop computer only §Fix the position of the notebook and the access point §Use program to start the measuring routine §Repeat the experiment several times

One sender and one receiver

Two senders and one receiver As the packet size is small, the OS scheduler also pay a role in the performance

Findings in Wireless LAN §Two different best effort data streams running simultaneously will compete one another §Two different guarantee data streams match the user specification

Wired LANs with router §Network Configuration: Sender’s Computer  RSVP-aware Router  Receiver’s Computer

Best effort VS Guaranteed

Findings in GQoS Evaluation §The behaviour of GQoS in wireless environment is similar to that in wired environment except the bandwidth are different. §In Ethernet and wireless LAN environment, only the packet scheduler inside GQoS pay a role in providing services §When networks are interconnected by RSVP routers, the routers help GQoS to classify packets and hence give a better guaranteed service

Future Works §Evaluation part l Point out the weakness of GQoS l Building QoS applications in Windows §Implementation in System Level l Purpose a new QoS scheme on Linux l Implement our own QoS scheme which lies on RSVP and compare it with GQoS §Implementation in Application Level l Provide QoS in COBRA and build a QoS manager at COBRA service level

Q & A Session Please feel free to ask

The End Thank you