1. 2000/3/9QoS Introduction1 References: 1.Paul Ferguson and Geoff Huston, Quality of Service, John Wiley & Sons, 1998. 2.Xipeng Xiao and Lionel M. Ni, “Internet QoS: A big picture”, IEEE Network, pp. 8 - 18, March/April, 1999. 3.Brian E. Carpenter and Dilip D. Kandlur, “Diversifying Internet delivery”, IEEE Spectrum, pp. 57 - 61, November 1999.

2. 2000/3/9QoS Introduction2 Why Integrating Services in a Network? n Today, different services use different technologies u Telephony, video, leased line, etc. use circuit switching F Dedicated bandwidth F Predictable performance F Poor utilization F Expensive u Email, WWW, FTP, etc. use packet switching F Unpredictable performance due to best-effort service F Use oversubscription (statistical multiplexing) to improve utilization Packets are dropped and traffic is slow down at congestion F Inexpensive

3. 2000/3/9QoS Introduction3 Which Integrated Network? n We want one network/technology for all services u Packet switching is the way to go, but which one?  IP, IPX, X.25, ATM … Data Voice Video VoiceDataVoiceVideo Separate connections TDMIntegrated (better efficiency) Wasted bandwidth

4. 2000/3/9QoS Introduction4 What is Quality of Service? Application file transfer e-mail Web documents real-time audio/video stored audio/video interactive games instant messaging Data loss no loss loss-tolerant no loss Bandwidth elastic audio: 5kbps-1Mbps video:10kbps-5Mbps same as above few kbps up elastic Time Sensitive no yes, 100’s msec yes, few secs yes, 100’s msec yes and no n What is QoS? u Any mechanism that maps traffic into different classes, which can be administered differently throughout the network

5. 2000/3/9QoS Introduction5 Why is QoS Compelling? n QoS may give a service provider a competitive advantage over the others u Service Level Agreement (SLA) F 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 u Give preference to mission-critical traffic u Fair resource sharing

6. 2000/3/9QoS Introduction6 End-to-end QoS n What a user perceives is the end-to-end QoS n End-to-end QoS relies on u Network QoS u Server QoS u Interoperation of the two

7. 2000/3/9QoS Introduction7 Network QoS n Over-engineering is acceptable only for a well- defined scope u Over-engineering in WAN is economically prohibitive! n QoS implementation is based on a set of policies u Traffic classification and differentiation u Admission control u Preferential queuing u Congestion management u Path selection u etc.

8. 2000/3/9QoS Introduction8 Network QoS Solutions n Integrated services (IntServ) u Each connection (or flow) makes its own service requirement  Network supports each connection ’ s needs u Example: ATM, IP+RSVP u Not scalable. Suitable for corporate or campus intranet n Differentiated services (DiffServ) u Packets of a connection are classified into one of a finite number of classes u Network handles packets according to their class levels u Scalable well, good for large internet

9. 2000/3/9QoS Introduction9 Network QoS Solutions (Continued) n Multiprotocol label switching (MPLS) u Packets are attached a fixed-sized label by edge router before entering core network u Core router processes packets according to the labels only

10. 2000/3/9QoS Introduction10 Server QoS n Improvement for single service u Service replication (for www service) F DNS-based approach F Adaptive content delivery F Server cluster F Caching F Peer-to-peer (P2P) systems n Additional topics u Ad hoc networks F Wireless sensor networks