Sidevõrgud IRT 0020 loeng 6 04. okt. 2005

1. SidevõrgudIRT 0020loeng 6 04. okt. 2005 Avo Otstelekommunikatsiooni õppetool, TTÜ raadio- ja sidetehnika inst.avo.ots@ttu.ee

2. Q o S Shouldn’t you have some kind of equipment or something? It’s the Quality of the Service, our methods are not always apparent.

3. The Hidden Costs • WAN Over-provisioning • LAN Over-provisioning • Increased administrative costs • Extensive Troubleshooting • Unintended PSTN usage • Monitoring and measurement • Problems grow as network size increases Negative IP Telephony Business Case Hidden Costs of Convergence Positive IP Telephony Business Case

4. Voice not just another IP data application… Enterprise customers have high expectations: “No tolerance for poor voice, it has to be toll quality” “Voice goes down – they are on the phone” “Don’t want to lose business because of QoS” Voice inherently different from most data applications Intolerant of delays, packet loss and jitter Performance essential to the delivery of the service Voice specific application behavior Yet Another Data Application

5. Predominant QoS technology in use today Bandwidth allocated per traffic classes (via DSCP) Traffic Classification and Conditioning at edge Per Hop Behavior at interior nodes Queuing and Dropping according to priority & bandwidth Queuing must be configured for minimum packet delay Easy for endpoints, scales well, CPU intensive DiffServ: Has no end-to-end network/service view Limited Call Admission Control Scheme High priority packets can be dropped when congested Often difficult to configure and maintain Doesn’t always guarantee high quality DiffServ

6. Reserves resources end-to-end to provide service guarantees Uses the RSVP protocol which signals per flow QoS requirements to the network If reservation succeeds, flow has end-to-end guaranteed bandwidth Includes an inherent call admission control mechanism Ideal for real-time traffic such as voice and video Providing benefits similar to circuit switching Not as heavily used due to perceived drawbacks: Setup times, I.e. post-dial delay Issues due to per-flow behavior Amount of state information and overhead (IntServ)

7. IP Solution Easy to Manage Operations Savings MediaIP Director Bandwidth Savings Qos Engineering Traffic Engineering, Forecasting and Optimization MediaIP Controller Flow Aggregation, QoS/Access Control Integrated Services Diffserv (with LLQ) Any Infrastructure Dynamic Pro-active Adaptable Gateway Router Switch PSTN/ISDN Savings Multiservice Applications Video IP Telephony Content

8. Traditional approach for data networks… No mechanism for QoS Is actually best-effort Overprovision where? Expensive Converged Networks: “Bursty” Traffic 3X to 5X not sufficient Congestion still occurs Packet Counts 5000 4500 4000 3500 5x 3000 4x Packets 2500 3x 2000 1500 2x 1000 Mean 500 0 0 1 2 3 4 Hours Over-Provisioning Bandwidth Over-Provisioning

9. PSTN The Benefits and ROI from QoS Operations Savings Fewer PSTN Trunks Operations Center Reduced PSTN Minutes Reduced ISDN Minutes Legacy PBX IP PBX Enterprise WAN Network Access Bandwidth Savings WAN Bandwidth Savings

10. 384 Kbps Video (30 fps) “I” Frame 1024–1518 Bytes “I” Frame 1024–1518 Bytes 600Kbps 30pps “P” and “B” Frames 128–256 Bytes 15pps 32Kbps • “I” frame is a full sample of the video • “P” and “B” frames use quantization via motion vectors and prediction algorithms