1 / 12

Beyond TCP Congestion Control

Beyond TCP Congestion Control. 2007. Extensions to TCP. End-to-end congestion control Selective acknowledgements: TCP SACK Delay-based congestion avoidance: TCP Vegas TCP-Friendly Rate Control: TFRC Binomial Congestion Control Router - assisted Congestion Control

afram
Download Presentation

Beyond TCP Congestion Control

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Beyond TCP Congestion Control 2007

  2. Extensions to TCP • End-to-end congestion control • Selective acknowledgements: TCP SACK • Delay-based congestion avoidance: TCP Vegas • TCP-Friendly Rate Control: TFRC • Binomial Congestion Control • Router - assisted Congestion Control • Active Queue Mgmt. (AQM) and RED • Explicit congestion notification: ECN • eXplicit Control Protocol: XCP • Discriminating between congestion losses and other losses: cross-layer signaling and guesses losses

  3. Outline • TCP-Friendly Rate Control (TFRC) • Binomial Congestion Control

  4. TCP-Friendly • Any alternative congestion control scheme needs to coexist with TCP in FIFO queues in the best-effort Internet, or be protected from TCP in some manner. • To co-exist with TCP, it must impose the same long-term load on the network: • No greater long-term throughput as a function of packet loss and delay so TCP doesn't suffer • Not significantly less long-term throughput or it's not too useful

  5. TFRC: TCP-Friendly Rate Control • Equation-based congestion control • Rate-based • Use a model of TCP's throughout as a function of the loss rate, RTT and RTO directly in a congestion control algorithm • If transmission rate is higher than that given by the model, reduce the transmission rate to the model's rate • Otherwise increase the transmission rate • Much slower increase than TCP • Decrease is also slower • 4 – 8 RTTs to halve speed

  6. An Improved "Steady State" Model A pretty good improved model of TCP Reno, including timeouts, Sigcomm 1998: • 1st term corresponds to simple Loss Model • 2nd term corresponds to complicated timeout behavior • Is critical in situations with > 5% loss rates where timeouts occur frequently

  7. TFRC Details • The devil's in the details • How to measure the loss rate? • How to respond to persistent congestion? • How to use RTT and prevent oscillatory behavior? • Not as simple as first thought

  8. TFRC Performance (Simulation)

  9. TFRC Performance (Experimental)

  10. Is AIMD the Only Answer? • Akella et al.: exploring congestion control • AIAD with a tiny bit of MD works better than AIMD • Binomial cc: Bansal and Balakrishnan • Nonlinear window adjustment algorithms • Can be TCP-friendly, and smoother (for media)

  11. Binomial Congestion Control • In AIMD • Increase: Wn+1 = Wn +  • Decrease: Wn+1 = (1- ) Wn =Wn -  Wn • In Binomial • Increase: Wn+1 = Wn + /Wnk • Decrease: Wn+1 = Wn -  Wnl • k=0 & l=1  AIMD • l < 1 results in less than multiplicative decrease • Good for multimedia applications

  12. Binomial Congestion Control • Rate ~ 1/ (loss rate)1/(k+l+1) • If k+l=1 rate ~ 1/p0.5 • TCP friendly if l =< 1 • AIMD (k=0, l=1) is the most aggressive of this class • Good for applications that want to probe quickly and can use any available bandwidth

More Related