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Effective Traffic Control Strategies for Routers: The Red Police Algorithm

Modern routers face challenges managing high-bandwidth flows. The Red Police Algorithm aims to address congested routers by controlling large flows, employing CHOKe scheduling, and using the SEC algorithm. By partitioning drop history and targeting specific flows, it provides efficient traffic management. The algorithm adapts to changing flow rates and network conditions, offering an effective solution for handling traffic bottlenecks. Explore the innovative RED-PD approach and its benefits for router performance optimization.

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Effective Traffic Control Strategies for Routers: The Red Police Algorithm

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  1. By Sam Rossoff

  2. Controlling High-Bandwidth Flows at the Congested Router The Red Police By Ratul MahajanSally Floyd andDavid Wetherall By Sam Rossoff

  3. Networking 101 • Modern routers use a simple FIFO queue • When a router runs out of room to store packets new packets are dropped from the end of the queue Destination Internet Router | | | | | | | | | | | | | By Sam Rossoff

  4. Pushy Flows • Because a router's bandwidth is fixed, if a single flow is very large it will hog up all the room on the queue • Solution: Restrict the bandwidth of large flows By Sam Rossoff

  5. Try Try Again • Previous approaches break up into two categories • Continuum: (SFQ, FIFO, etc) • Scheduling: (CSFQ, FRED, RED, etc) By Sam Rossoff

  6. By Sam Rossoff Schedules and You • CHOKe • Find a packet at random, compare to incoming packet and nuke both if same flow. • Limited performance: • When there are too many high • With high UDP flows • CSFQ: Core Stateless Fair Queuing • Estimates packets fair share and drops based on rate estimate and fair share • Requires: • Core “island” of routers • Extra field in packet header

  7. By Sam Rossoff The Design • We really only need to worry about the big flows

  8. On Beyond Zebra • This works because: • A Fraction of the flows make up most of the bandwidth • Predictable effect on the traffic going through the router By Sam Rossoff

  9. By Sam Rossoff The SEC Algorithm • Use the RED drop history • To identify flows that are sending more than ƒ(r,p) , the reference TCP flow’s rate( RTT r and packet drop rate p). And thus dropping more than once in CL(r,p) seconds.

  10. By Sam Rossoff Epoch's are Fun • Congestion epoch length • Maintaining the packet drop history over K x CL(R,p) seconds • Partitioning the history into M lists • RED-PD identifies flows with losses in at least K of M lists • K = 3, M = 5, r = 40ms and p = 1%

  11. By Sam Rossoff But, Does it work? Identifying: g x f(R, p) Flow 1: .1mbps Flow 2: .5 mbps Flow i: Rate(i-1) + .5mbps

  12. By Sam Rossoff I'm Going to Go with Yes • RED-FD responds based on the drop rate. • Few drops and flows run wild 1 CBR flow and 9 TCP flows The CBR flow starts with a rate of 0.25 Mbps, increases it to 4 Mbps at t=50s, and decreases it back to 0.25 Mbps at t=250s. The RTT of the TCP flows ranged from 30 to 70 ms.

  13. By Sam Rossoff And Other Fun Facts on Cereal Boxes • For flows identified as unresponsive, RED-PD increases the drop probability more quickly. • Memory Required is only: • RED-PD targets flows dropped from either itself, RED, or overflow • Nets of these routers have faster response times and are more effecient.

  14. By Sam Rossoff RED-PD Protects the Innocent • Even works when there are a few flows of enormous bandwidth coming in. • Flow 10: 5mbps • Flow 11: 3mbps • Flow 12: 1mbps

  15. Now for my opponent who is a poopoo head Which is Why I Think I Would Make a Good President By Sam Rossoff

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