QoS Introduction

1. QoS Introduction • References: • Paul Ferguson and Geoff Huston, Quality of Service, John Wiley & Sons, 1998. • Xipeng Xiao and Lionel M. Ni, “Internet QoS: A big picture”, IEEE Network, pp. 8 - 18, March/April, 1999. • Brian E. Carpenter and Dilip D. Kandlur, “Diversifying Internet delivery”, IEEE Spectrum, pp. 57 - 61, November 1999. QoS Introduction

2. Why Integrating Services in a Network? • Today, different services use different technologies • Telephony, video, leased line, etc. use circuit switching • Dedicated bandwidth • Predictable performance • Poor utilization • Expensive • Email, WWW, FTP, etc. use packet switching • Unpredictable performance due to best-effort service • Use oversubscription (statistical multiplexing) to improve utilization • Packets are dropped and traffic is slow down at congestion • Inexpensive QoS Introduction

3. Data Video Voice Data Voice Video Voice Video Separate connections TDM Integrated (better efficiency) Wasted bandwidth Which Integrated Network? • We want one network/technology for all services • Packet switching is the way to go, but which one? • IP, IPX, X.25, ATM… QoS Introduction

4. What is Quality of Service? Time Sensitive no no no yes, 100’s msec yes, few secs yes, 100’s msec yes and no Application file transfer e-mail Web documents real-time audio/video stored audio/video interactive games instant messaging Bandwidth elastic elastic elastic audio: 5kbps-1Mbps video:10kbps-5Mbps same as above few kbps up elastic Data loss no loss no loss no loss loss-tolerant loss-tolerant loss-tolerant no loss • What is QoS? • Any mechanism that maps traffic into different classes, which can be administered differently throughout the network QoS Introduction

5. Why is QoS Compelling? • QoS may give a service provider a competitive advantage over the others • Service Level Agreement (SLA) • Service contract between service subscriber and service provider • Per user: availability, bandwidth • Per connection/class: bandwidth, burst size, delay, jitter, loss • QoS can regulate network resource usage to conform to an organization’s objectives • Give preference to mission-critical traffic • Fair resource sharing QoS Introduction

6. End-to-end QoS • What a user perceives is the end-to-end QoS • End-to-end QoS relies on • Network QoS • Server QoS • Interoperation of the two QoS Introduction

7. Network QoS • Over-engineering is acceptable only for a well-defined scope • Over-engineering in WAN is economically prohibitive! • QoS implementation is based on a set of policies • Traffic classification and differentiation • Admission control • Preferential queuing • Congestion management • Path selection • etc. QoS Introduction

8. Network QoS Solutions • Integrated services (IntServ) • Each connection (or flow) makes its own service requirement • Network supports each connection’s needs • Example: ATM, IP+RSVP • Not scalable. Suitable for corporate or campus intranet • Differentiated services (DiffServ) • Packets of a connection are classified into one of a finite number of classes • Network handles packets according to their class levels • Scalable well, good for large internet QoS Introduction

9. Network QoS Solutions (Continued) • Multiprotocol label switching (MPLS) • Packets are attached a fixed-sized label by edge router before entering core network • Core router processes packets according to the labels only QoS Introduction

10. Server QoS • Improvement for single service • Service replication (for www service) • DNS-based approach • Adaptive content delivery • Server cluster • Caching • Peer-to-peer (P2P) systems • Additional topics • Ad hoc networks • Wireless sensor networks QoS Introduction