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HSTCP-LP: A Protocol for Low-Priority Bulk Data Transfer in High-Speed High-RTT Networks. Aleksandar Kuzmanovic Edward W. Knightly Rice University R. Les Cottrell SLAC/SCS-Network Monitoring. Rice Networks Group http://www.ece.rice.edu/networks. Motivation.

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hstcp lp a protocol for low priority bulk data transfer in high speed high rtt networks

HSTCP-LP: A Protocol for Low-Priority Bulk Data Transfer in High-Speed High-RTT Networks

Aleksandar Kuzmanovic

Edward W. Knightly

Rice University

R. Les Cottrell

SLAC/SCS-Network Monitoring

Rice Networks Group

http://www.ece.rice.edu/networks

motivation
Motivation
  • Traditional view of service differentiation:
    • High priority: real-time service
    • Best-effort: everything else
  • What’s missing?
    • Low-priority (receiving only excess bandwidth)
    • Lower than best-effort!
      • Non-interactive applications, bulk download
        • It will last long anyway...
      • Speeds up best-effort service (e.g., web)
applications for low priority service
Applications for Low Priority Service
  • LP vs. fair-share:
    • Bulk downloads
      • SLAC->CERN
      • Improve my other

applications

  • LP vs. rate-limiting:
    • P2P file sharing
      • Often rate limited
      • Isolation vs. sharing
problem formulation design objectives
Problem Formulation & Design Objectives
  • Low-priority service objectives
    • Utilize the “excess/available” capacity
      • What no other flows are using
    • TCP-transparency (non-intrusiveness)
    • Inter-LP flow fairness (fair-share of the available bandwidth)
origins of the available bandwidth
Origins of the Available Bandwidth
  • Why is excess bandwidth available when TCP is greedy?
    • Time-of-day effects
      • Night- vs. day-time traffic
    • Short-lived flows
      • Majority traffic is web browsing
    • TCP is imperfect
      • Low-aggregation regimes
tcp fairness
TCP fairness
  • In presence of TCP

cross-traffic:

    • TCP achieves fairness
illustration of tcp transparency
Illustration of TCP Transparency
  • LP flow utilizes only

excess bandwidth

    • Does not reduce the throughput of TCP flows
fairness among lp flows
Fairness Among LP Flows
  • Inter-LP-fairness is

essential for

simultaneous

file transfers

hstcp lp a congestion control protocol
HSTCP-LPA Congestion Control Protocol
  • Problem
    • TCP-LP [Infocom03]
      • AIMD control not

suitable for high speeds

  • Approach
    • Add HSTCP [Floyd03] high-speed mechanisms
  • Challenge
    • Develop large windows and achieve low-prioritization at the same time
early congestion indication
Early Congestion Indication
  • For transparency, HSTCP-LP must know of congestion before non-LP flows
  • Idealized objective: buffer threshold

indication

  • Endpoint inference: one-way delay threshold
reverse cross traffic
Reverse Cross-Traffic
  • HSTCP-LP uses one-way packet delays (RFC1323) for congestion indication
    • Source-destination

time stamping

    • Synchronized clocks

not needed

  • One-way delay:
    • Eliminates the impact

of the reverse cross-traffic

      • HSTCP-LP can loose Gb/s of available bandwidth if RTT is used
hstcp lp timeline illustration
HSTCP-LP Timeline Illustration
  • Reach high throughput ...quickly in slow-start
  • Estimate one-way ...delay and compute ...delay threshold
hstcp lp timeline illustration1
HSTCP-LP Timeline Illustration

Apply HSTCP response function with early congestion indications

hstcp lp timeline illustration2
HSTCP-LP Timeline Illustration
  • HSTCP response ...function above ...Low_Window
  • TCP-LP response ...function below ...Low_Window
  • Send 1 packet/RTT
hstcp lp timeline illustration3
HSTCP-LP Timeline Illustration

HSTCP increase function with early congestion indications

implementation and experiments
Implementation and Experiments
  • Linux-2.4.22-web100 kernel:
    • HSTCP HSTCP-LP
      • Time stamping, modified congestion control...
  • Paths:
    • Stanford, CA

Ann Arbor, MI

    • Stanford, CA

Gainesville, FL

    • Available bitrate

~ 450 Mb/s

low priority background data transfer
Low-Priority Background Data Transfer
  • HSTCP-LP is highly non-intrusive to other advanced TCP stacks
    • Strict prioritization for larger bottleneck queue lengths
    • Lighter prioritization for (max_delay < 50 ms)
utilizing excess bandwidth
Utilizing Excess Bandwidth
  • Extensive experiments on a number of high bandwidth-delay production networks
    • no cross-traffic
    • periodic UDP cross-traffic
    • reverse cross-traffic
    • http://www.slac.stanford.edu/~hadrien
  • HSTCP-LP utilizes 80-127% of the available bandwidth when compared to other high-speed stacks
    • 127% when transmission buffer (tqueuelen) is large
conclusions
Conclusions
  • HSTCP-LP: a new protocol for high bandwidth-delay production networks
    • General low priority service (compared to “best-effort”)
  • Attractive for low-priority bulk downloads: ftp, web updates, P2P
  • HSTCP-LP is incrementally deployable
    • Sender side modification of HSTCP without changes to routers
  • Implementation and evaluation in the Internet

http://www.ece.rice.edu/networks/TCP-LP

questions
Questions

http://www.ece.rice.edu/networks/TCP-LP