Department of Electrical Engineering Computer Networking Lab

1. Integrated-Service versus Differentiated-Service Networks 許蒼嶺 教授 國立中山大學 電機工程學系 Department of Electrical Engineering Computer Networking Lab National Sun Yat-Sen UniversityProf. Tsang-Ling Sheu

2. Outline • Integrated Services • Traffic Model • RSVP • Differentiated Services • Architectures • Traffic Classes and DSCP • Queuing Disciplines • Survey of Papers

3. Quality of Services • Over-Provisioning • Priority Queuing • Per-Flow : Integrated Service, Intserv [RFC1633] • Per-Class : Differentiated Services, Diffserv [RFC2475]

4. Integrated Services • Resource ReSerVation Protocol • Controlled-Load Service - RFC 2212 • Guaranteed Service - RFC 2211

5. Integrated Services • Modules in Integrated-Service Traffic Model • Admission Control • Determine if QoS Request Should be Granted • Traffic Classifier • Map Packets/Flows to Service Classes • Packet Scheduler • Forward Packets Based on Service Classes

6. IntServ Traffic Model Router Host RSVP Reservation Routing Protocols RSVP Reservation Admission Control Classifier Packet Scheduler Classifier Packet Scheduler IP Data Flow

7. Integrated Services • Guaranteed Services • For Delivering Real-Time Applications • Provides an Assured Level Services • Bandwidth • End-to-End Delay Bound • No Queuing Loss • Controlled-Load Services • Service Equivalent to Best-Effort Flows

8. RSVP Issues • RSVP only Suits for Long-Duration Applications • Too Expensive for WWW Transfers • RSVP only Suits for Small-Size Networks • Leads to too many Link States and Signaling Traffic • RSVP Requires Application Supports • Knowledge of Application QoS • QoS API

9. RSVP

10. Diffserv Architecture

11. DiffServ Issues • Scaling • Pushes Complex Forwarding Operations to Boundary Routers • Control and management • Rely on New Configuration or Management Protocols • Bandwidth Broker (BB) • Suits for a Small-Size Network • Distributed BB • Billing and Accounting • Based on Negotiated Traffic Profiles

12. Management and Billing Priority Levels IP Addresses TCP Ports Video Conf. FTP Telnet WWW SMTP BBS SNMP Time of Day

13. Bandwidth Broker BandwidthBroker Interior Routers Packets Out Packets In Boundary Router Boundary Router

14. Diffserv Field in IPV6 Header

15. Diffserv – PHB Group • DF (Default Forwarding, Best-Effort) • DSCP : 000000 • EF (Expedited Forwarding) • DSCP : 101110 • AF (Assured Forwarding) • DSCP : 4 Class, 3 Drop Precedence

16. Classifier & Traffic Conditioner

17. First-Come-First-Serve (FCFS) • Simplest Queue • Packet will be dropped when queue is full • Rear or front dropping

18. Priority Queue (PQ) • Packets with higher-priority will always be sent first • Starvation in lower-priority queue

19. Round-Robin (RR) 7 4 1 8 5 2 6 9 3

20. Weighted Round Robin (WRR)M. Katevenis, IEEE Journal on Selected Areas in Communications, 1991 • General case of Round Robin • More weight with higher-priority class

21. Weighted Fair Queue (WFQ)A. Demers, SIGCOMM’ 89 • Provide fairness in variable-length IP packets • Packets sent by the order of estimated completion time

22. WFQ

23. Deficit Round Robin (DRR)M. Shreedhar, IEEE/ACM Transactions on Networking, 1996 • WFQ is not easy to be implemented, O(logP) • DRR • Round Robin fashion, O(1) • Use Quantum instead of Weight • Use Deficit Counter to provide fairness

24. DRR

25. Token Bucket (TB) • Leaky Bucket:Traffic Shaping • Token Bucket:Shaping with more burst tolerance

26. Random Early Detection (RED) Minimum Threshold (Minth) Maximum Threshold (Maxth) Average Queue Size (avg) Marking Probability (Pmax)

27. Random Early Detection(RED)S. Floyd, IEEE/ACM Transactions on Networking, 1993 • Random drop or mark packets before buffer overflow

28. RED with In/Out Bit (RIO)D. D. Clark, IEEE/ACM Transactions on Networking, 1998 • Different marking probability for In/Out packet

29. RED with In/Out bit (RIO) In Packet : Minimum Threshold (Minth_in) Maximum Threshold (Maxth_in) Average Queue Size (avg_in) Marking Probability (Pmax_in) Out Packet : Minimum Threshold (Minth_out) Maximum Threshold (Maxth_out) Average Queue Size (avg_total) Marking Probability (Pmax_out)

30. Proportional DiffServC. Dovrolis, IEEE Network, 1999 • Absolute DiffServ (WRR, DRR) • Use static resource reservation instead of dynamic resource reservation • Proportional DiffServ (WTP, DWFQ, PLQ) • Provide QoS differentiation between traffic classes • Predictable: • High-priority class must have better or the same QoS as low- priority class • Controllable • Provide a time tuning knob to adjust the differentiation between classes

31. Waiting Time Priority (WTP)C. Dovrolis, IEEE/ACM Transactions on Networking, 2000 • General case of Time-Dependent Priorities [L. Kleinrock, Queuing Systems, 1976] • Delay Proportional Parameter δi • Active(Busy) Set B(t) • Normalized Head Waiting Time • Packet with the most waiting time will be sent first

32. Dynamic WFQ (DWFQ)Chin-Chang Li, ICCCN, 2000

33. Probabilistic Longest Queue (PLQ)Jung-Shian Li, GLOBECOMM’01

34. PQ with EF Token Bucket • EF PHB has the highest priority • Use a Token Bucket to limit EF maximum bit rate

35. Priority Queue with Quantum (PQWQ) • Provide fairness between PHBs • Use counters for all PHBs in order to limit bytes sent in one round • Quantum values will be added to counters after one round • Provide low delay to EF PHB • EF PHB has the highest priority • If counter is enough, higher priority PHB will be sent first in one round • Avoid the delay by Round Robin fashion

36. PQWQ (cont.)

37. Diffserv Potential Problems • Ineffectual End-to-End QoS guarantee • Unfair bandwidth sharing • Packets only dropped at congested links when congestion

38. Various Diffserv Architectures • Packet-Marking Engine (PME)[Wu-Chang Feng, 1999] • Feedback Controlled Diffserv[Hungkei Chow, 1999] • Diffserv in MPLS[Y. Bernt, 2000] • RSVP in Diffserv[I. Andrikopoulos, 1999]

39. Packet-Marking Engine (PME) • New Packet-Marking Engine • TCP-like algorithm and Modified TCP congestion control • Dynamic Marking probability (mprob) • Adv : • TCP-friendly algorithms • Adative packet marking to improve end-to-end throughput • Traffic fairness • Disadv : • 1-bit priority for packet marking • Support TCP traffic only • Update network interface in host/nodes

40. Feedback Controlled Diffserv • New FC-DS nodes • Probe/Report control packet • Adaptvie QoS • Adv : • Current network status report • Adative traffic conditioning • Fair network resources allocation • Disadv : • Upgrade DS nodes to support FC scheme • More processing complexity in FC-DS ingress nodes • Extra processing of probe control packets

41. Diffserv in MPLS

42. RSVP in Diffserv

43. Self-Adaptive Diffserv Router

44. Self-Adaptive Diffserv Architecture

45. Self-Adaptive Control Message Format

46. PHB DSCP Field SAI Field Description EF 101110 0xxxxxx Increase weight for WRR EF 101110 1xxxxxx Decrease weight for WRR AF Old DSCP New DSCP Change to new DSCP BE 000000 0xxxxxx Increase weight for WRR BE 000000 1xxxxxx Decrease weight for WRR 6-Bit SAI Field

47. CU value Packet Type 00 Normal Data Packet 10 Normal Control Packet 01 Congested Data Packet 11 Congested Control Packet 2-Bit CU Field

48. Conclusions • Integrated Services • Per flow QoS • RSVP • DiffServ Architectures • Per Class QoS • Traffic Classification • Queuing and Scheduling • WRR, WFQ, DRR, Token Bucket, Proportional Delay, etc. • MPLS and DiffServ