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Dynamic-CBT

Dynamic-CBT. Jae Chung and Mark Claypool. Better Performing Active Queue Management for Multimedia Networking. Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA. http://perform.wpi.edu/. Outline. Introduction CBT D-CBT Evaluation Issues.

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Dynamic-CBT

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  1. Dynamic-CBT Jae Chung and Mark Claypool Better Performing Active Queue Management for Multimedia Networking Computer Science Department Worcester Polytechnic Institute Worcester, Massachusetts, USA http://perform.wpi.edu/

  2. Outline • Introduction • CBT • D-CBT • Evaluation • Issues

  3. Internet Routers Today • Volume of traffic increasing • More simultaneous active flows • Increase in multimedia flows • Tight timing constraints • Different flow-control mechanism than TCP • Emphasis on Congestion Control and Fairness among active flows

  4. Congestion handling? Fairness (tcp, other)? Support QoS? Current Router Queue Mgmt Drop Tail (FIFO) Resource Reservation Active Queue Mgmt ... CBQ RED FRED ... ( Floyd, Jacobson ‘95) ( Floyd, Jacobson ‘93) (Lin, Morris ‘97) Class-Based Threshold (CBT) (Parris, Jeffay, Smith ‘99)

  5. CBT Design

  6. CBT - Pros and Cons • Pros:RED + Class-Based Isolation • Early congestion notification • Protect TCP and protect Tagged UDP (MM) • Different classes of flows coexist with predefined fairness • Cons:CBQ function w/o admission control • Fairness for changing traffic mixes • Utilization on outgoing link • Changes “Best-Effort” nature of Internet

  7. Dynamic-CBT (D-CBT) Drop Tail (FIFO) Resource Reservation Active Queue Mgmt ... CBQ RED FRED ... Class-Based Threshold (CBT) Dynamic-CBT

  8. Count Active Flows In Each Class UpdateClass Avgs & RED Avg Calc Thrsh Thrsh* Test Calc Thrsh Thrsh* Test D-CBT Design RED Tagged UDP (MM) Early Drop Test Queue Manager Untagged UDP Classify TCP * Threshold Test is activated when red_avg > red_min

  9. Evaluation using NS • Developed a flow-controlled Multimedia Application (for tagged UDP class) • AIMD Media Scaling (5 discrete rates) • “MPEG-1 like” transmission rates • Implemented and validated CBT • Implemented D-CBT and measured congestion time fairness • RED vs. CBT vs. D-CBT

  10. 25Mbps, 5ms 25Mbps, 5ms 25 FTP-TCP s1 r2 25Mbps, 20ms 10 MM-UDP s2 r2 n1 n2 s66 r66 n1-n2: q_size = 60 RED: max_th = 15 min_th = 5 qweight = 0.002 max_prb = 0.1 CBT: mmu_th = 2.9 udp_th = 0.6 2 CBR-UDP (5Mbps each) s67 r67 30 FTP-TCP 0 10 20 30 Second Simulation (RED, CBT, D-CBT)

  11. Fairness: RED

  12. Fairness: CBT

  13. Fairness: D-CBT

  14. D-CBT Issues • Tagging UDP packets • Who tags packets? (End Host? ISP?) • Which field of IP header to use? • IPv4: Unused Bit in Type-Of-Service Field • IPv4: Another Protocol in Protocol Field • IPv6: Use Priority Field • Define a flow • IPv4: Source-Destination Address • IPv6: Plus Flow-ID

  15. D-CBT Issues • Active Flow Counting (Overhead) • For every incoming packet, insert or update<dest-addr, flow-id, local-time> info and update count • Hash Table - O(1) • Every ms, delete old flows and update count • Hash Table - O(n) • Measure Active Flow Counting overheads: • Linux implementation • Processing Time and Memory Usage

  16. D-CBT Issues • Test D-CBT with other (available) flow-controlled MM Applications • Effect of the thresholds on MM quality • Sensitivity of D-CBT to RED parameters • How many different classes are needed? • Example • 1 class is RED • 1 class per flow is FRED • Overhead per class

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