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Applications of Virtual Packet Fair Queueing

Applications of Virtual Packet Fair Queueing. 李孝治. Outline. Introduction to VPFQ CDMA systems 2-1 Multirate CDMA Systems 2-2 Multicode CDMA Systems 2-3 Optical CDMA Systems WAN with Backup Leased Lines Grid Computing The Need for In-Sequence Packet Delivery. 1. VPFQ.

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Applications of Virtual Packet Fair Queueing

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  1. Applications of Virtual Packet Fair Queueing 李孝治

  2. Outline • Introduction to VPFQ • CDMA systems 2-1 Multirate CDMA Systems 2-2 Multicode CDMA Systems 2-3 Optical CDMA Systems • WAN with Backup Leased Lines • Grid Computing • The Need for In-Sequence Packet Delivery

  3. 1. VPFQ • Virtual-link Packet Fair Queuing (VPFQ) ensures fair and in-sequence transmission of packets over a virtual transmission link that contains multiple physical links of different capacities.

  4. We propose three assignment strategies: • Conservative Fair Assignment (CFA) • An eligible packet is assigned to an idle server if the assignment is feasible. • Eligible: smallest Sv(pk) at the head of each queue • Feasible: in-sequence • Greedy Assignment (GA) • An eligible packet is assigned to a server that can finish transmitting the packet at the earliest time if the assignment is feasible. • Virtual Assignment (VA) • An eligible packet is assigned to an idle server. • Out-of-order packets are reordered at the input of the next switching element.

  5. Packet Fair Scheduler In-sequence Assignment Flow 1 Flow 2 Flow 3 2 PhysicalChannel 1 Server 1 Physical Channel 2 1 Server 2 Conservative Fair Assignment (CFA)

  6. <開始> • 當建立一個串流時，而且所有的伺服器都是閑置時： • 分派最小開始服務時間的封包給一個當時容量最大的伺服器i； • 當一個封包結束傳送時： • 分派開始服務時間最小的封包給不造成失序而且最小結束服務時間的伺服器i：Fr(pfk, i) = min{ EIi(pfk) + lfk/Ci > Fr(pfk-1, j)| iI(t)}，其中 I(t) 是在當時所有閑置伺服器的集合； • 若分派的結果會造成封包失序，則分派封包給造成失序但最小結束服務時間的伺服器i，然後排程器阻塞：亦即若Fr(pfk, i) = min{ EIi(pfk) + lfk/Ci > Fr(pfk-1, j)| iI(t)} = ，則Fr(pfk, i) = min{ EIi(pfk) + lfk/Ci ≦ Fr(pfk-1, j) | iI(t)}； • 若排程器阻塞，啟動 FST 計時器= Ib(pfk) = Fr(pfk, i) – Fr(pfk-1, j) 給伺服器 i。 • FST 計時器逾時： • 分派該 FST相關的被阻塞封包給該 FST相關的伺服器。 • <結束>

  7. Packet Fair Scheduler In-Sequence Assignment Flow 1 Flow 2 Flow 3 PhysicalChannel 1 Server 1 Physical Channel 2 Server 2 FIFO Greedy Assignment (GA)

  8. <開始> • 當至少還有一個伺服器是閑置的而且還有可行的封包要分派，或當一個串列剛成為主動： • 分派開始服務時間最小的封包，給不造成失序而且最小結束服務時間的伺服器i。如果有相同的伺服器符合，任意選擇其一。如果伺服器在忙碌中，將封包放入 FIFO。 • 重複步驟 1 直到所有伺服器都成為忙碌、排程佇列空了、或沒有可行的封包可以排程為止。 • 當一個封包結束傳送時： • 若該伺服器的佇列不是空，回返；否則分派開始服務時間最小的封包，給不造成失序而且最小結束服務時間的伺服器i。如果有相同的伺服器符合，任意選擇其一。如果伺服器在忙碌中，將封包放入 FIFO。 • 重複步驟 1 直到所有伺服器都成為忙碌、排程佇列空了、或沒有可行的封包可以排程為止。 • <結束>

  9. Realignment Receiver Packet Fair Scheduling Virtual Assignment Flow 1 Flow 2 Flow 3 PhysicalChannel 1 Server 1 Physical Channel 2 Server 2 Virtual Link Virtual Assignment (VA)

  10. <開始> • 當建立一個串流時，而且所有的伺服器都是閑置時： • 分派最小開始服務時間的封包給一個當時容量最大的伺服器i； • 當一個封包結束傳送時： • 分派開始服務時間最小的封包給最小結束服務時間的伺服器i：Fr(pfk, i) = min{ EIi(pfk) + lfk/Ci > Fr(pfk-1, j)| iI(t)}，其中 I(t) 是在當時 • <結束>

  11. Simulation Model • Environment • {Mesquite CSIM-18 & C++} @ Linux • Parameters • Number of servers • MaxFlow = 1 (s) • MaxFlow = 4 (m) • Flow Types • Discrete (0) , • Continuous (1) • Overlapping (2) • Server Capacity • Single Server: 1500 Kbps • Multi-Server - Same (0): 375 Kbps, 375 Kbps, 375 Kbps, 375 Kbps • Multi-Server - Different (1): 800 Kbps, 400 Kbps, 200 Kbps, 100 Kbps • Number of flows • 1, 2, 4, 6, 8, 10 (0 ~ 5)

  12. Packet Size • 20 Bytes ~ 64K Bytes • Packet Interarrival Time = 1 sec • Flow Weight = (CMIN / MaxFlow) / (1 + MaxWeight) = (64K / MaxFlow) / (1 + 5) • Simulation time: 200 sec. • Single server (SFQ) vs. Multi-server (CFA/GA/VA*)

  13. Virtual Time vs. Real Time

  14. Fairness

  15. Throughput

  16. Total Throughput

  17. Delay

  18. Blocking Interval

  19. Server Utilization

  20. 2. CDMA • “Cellular Land-Mobile Radio: Why Spread Spectrum”– Cooper, Nettleton, and Grybos, IEEE Communication Magazine, July 1979. • The first spread spectrum approach toland mobile radio. • The authors believe that spread spectrum can substantially improve the spectral efficiency of a cellular land-mobile radio system. • The authors acknowledge the existence of controversy and the fact that they do not know whether or not their scheme is economically viable.

  21. Characteristics of CDMA • More suitable for asynchronous access (e.g LAN, Internet) than for synchronous access (e.g. TDMA, FDMA, and WDM) • No scheduling is required. • No waiting time • Higher bandwidth is needed (e.g. optical fiber) • Higher bandwidth signal processing is needed.

  22. 2-1 Multirate CDMA • Multi-Rate Schemes in DS/CDMA Systems – Ottosson and Svensson, VTC 1995. • Multi-Modulation • Multi-Processing-Gain • Multi-Channel • Multi-Chip-Rate • Spreading Gain (Processing Gain) • N = B / R • B = System Bandwidth • R = Bit Rate

  23. * Variable Spreading Gain (VSG-CDMA) • ** Multicode (MC-CDMA) • *** Variable Chip Rate (VCR-CDMA)

  24. 2-2 Multicode CDMA • Multi-Code CDMA Wireless Personal Communication Networks– I and Gitlin, ICC 1995. • Performance of Multi-Code CDMA Wireless Personal Communication Networks– I and Gitlin, VTC 1995.

  25. 2-3 Optical CDMA • Spread Spectrum Fiber Optics Local Area Network Using Optical Processing– Prucnal, Santoro, and Ting, Journal of Lightwave Technology, May 1986. • Optical Orthogonal Codes: Design, Analysis, and Applications– Chung, Salehi, Wei, Transaction on Information Theory, May 1989.

  26. Multirate OCDMA • Codes for Direct-Detect CDMA Systems– Morenso and Maric, International Symposium on Information Theory. 1995

  27. Multicode OCDMA • Multicode direct-detection optical CDMA systems– Ohtsuki, International Symposium on Information Theory. 1997

  28. 3. WAN with Backup Leased Lines

  29. 4. Grid Computing • Adaptive Computing on the Grid Using AppLeS – Berman et. al., Transactions on Parallel and Distributed Systems, April 2003 • Grid: A a collection of resources (computational devices, networks, online instruments, storage archives, etc.) that can be used as an ensemble整體.

  30. 5. The Need for In-Sequence Packet Delivery • Done by every intermediate router/switch? • Done by the destination host? • TCP

  31. IV. CONCLUSIONS • Challenges • Usefulness of the applications of VPFQ. • Debug of the simulation programs. • Fixed-size packet • Interpretation and explanation of the simulation results. • In-Sequence Guaranteed Delivery vs. TCP at Destination End

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