1. An Integrated IP Packet Shaper and Scheduler for Edge Routers MSEE Project Presentation Student: Yuqing Deng Advisor: Dr. Belle Wei Spring 2002

2. Yuqing Deng’s MSEE Project Presentation 2 Outline Introduction Design Consideration Integrated Traffic Shaper and Scheduler Conclusion

3. Yuqing Deng’s MSEE Project Presentation 3 IP Traffic Management Challenges -- Quality of Service (QoS): End-to-end guarantees for delay, throughput and loss regulated in Service Level Agreement (SLA); Under the Differentiated Service (DS) scheme, this is expressed by varied priority levels for different data types ( video conferencing, ftp, email, etc); -- Fairness: Happens when multiple packet flows contend for limited resource; -- Traffic Shaping: To avoid potential congestion, bursty traffic has to be smoothed out. Introduction

4. Yuqing Deng’s MSEE Project Presentation 4 Introduction (cont’d) Implementation Algorithms: -- Scheduler: Fair Queuing (Per Flow Queuing); Weighted Round Robin (WRR); Priority Queuing; Timestamp; -- Shaper: Token Bucket; Leaky Bucket;

5. Yuqing Deng’s MSEE Project Presentation 5 Design Consideration Fair Queuing: needed? Precise scheduling, but complex implementation; Timestamp Integration: Should reflect both QoS and shaping feature; Virtual Output Priority Queue (VOPQ): Targeted queue for scheduled packets.

6. Yuqing Deng’s MSEE Project Presentation 6 Integrated Traffic Shaper and Scheduler Parser/ Search Engine Timestamp Generator Packet Memory Flow Status Lookup Table Clock Packets In Scheduler VOPQ Insertion n Packets Out to Switch Fabric

7. Yuqing Deng’s MSEE Project Presentation 7 Timestamp Generator/Flow Status LUT: Timestamp is calculated based on: 1) Token Bucket Algorithm for the shaping part; 2) Virtual Finish Time for QoS part; Algorithm (per flow base): TS k = TS k-1 + L k /r + S k ; Where S k = max [0, (TA k-1 + S k-1 + L k-1 /ρ – TA k )], with S 0 = 0; TA k /TS k : Arrival time/Timestamp for the current packet; TA k-1 /TS k-1 : Arrival time/Timestamp for the previous packet; L k / L k-1 : Size of the current/previous packet; ρ: token generation rate; r: transmission rate for the flow;

8. Yuqing Deng’s MSEE Project Presentation 8 Timestamp Generator/Flow Status LUT (cont’d): Flow status LUT keeps the following flow information: - Transmission rate; - Timestamp of previous packet; - Shaping adjustment of previous packet; - Arrival time of previous packet; - Priority level of the flow; Timestamp calculator updates flow status info when processing a new packet; Packet header info is sent to VOPQ along with its timestamp, based on its priority level;

9. Yuqing Deng’s MSEE Project Presentation 9 Timestamp Generator/Flow Status LUT: Block Diagram Buffer Flow Status Lookup Table Timestamp Calculator Packet header with timestamp Packet header

10. Yuqing Deng’s MSEE Project Presentation 10 Virtual Output Priority Queue (VOPQ) VOQ: has be extensively adopted for IP router, due to its better performance than normal Output Queue used in ATM switch; Priority Queue (PQ): used to implement Differentiated Service demand; a sorting/insertion technique is needed; VOPQ: a combination of VOQ and PQ; each output corresponds to a set of PQs in VOPQ; Implementation: Priority Content Addressable Memory (PCAM);

11. Yuqing Deng’s MSEE Project Presentation 11 VOPQ: Block Diagram PCAM Sorting Flow Priority Info Packet with TS ……. Scheduler

12. Yuqing Deng’s MSEE Project Presentation 12 Conclusion FQ not used but per flow status maintained: simplified design without sacrificing performance; Combined VOQ and PQ: further simplified design and increased speed; Integrated Timestamp: more function and flexibility; PCAM: fast sorting and scalable;