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TCP Libra - RTT-Fairness for TCP Authors: Gustavo Marfia*, Claudio E. Palazzi**, G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti** NRL – UCLA* Universita` di Bologna**. Recent Congestion Control Research at UCLA. TCP Evaluation Suite

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recent congestion control research at ucla

TCP Libra - RTT-Fairness for TCP

Authors: Gustavo Marfia*, Claudio E. Palazzi**,

G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti**

NRL – UCLA*

Universita` di Bologna**

Recent Congestion Control Research at UCLA

TCP Evaluation Suite

Authors: Hideyuki Shimonishi*, Tutomu Murase*, Cesar Marcondes**, M.Y. Sanadidi**, Mario Gerla**, Padmanabhan Vasu**

NEC Japan*

NRL – UCLA**

Presenter:

Cesar Marcondes

PhD Candidate CS/UCLA

Chicago, July 24 2007

IRTF/ICCRG Meeting

recent congestion control research at ucla1

Recent Congestion Control Research at UCLA

TCP Libra - RTT-Fairness for TCP

Authors: Gustavo Marfia*, Claudio E. Palazzi**,

G. Pau*, Mario Gerla*, M. Y. Sanadidi*, Marco Roccetti**

NRL – UCLA*

Universita` di Bologna**

Presenter:

Cesar Marcondes

PhD Candidate CS/UCLA

Chicago, July 24 2007

IRTF/ICCRG Meeting

motivation previous work
RTT fairness:

TCP sessions share same bottleneck => same bandwidth

Not true with TCP NewReno, bandwidth share is RTT-biased

TCP RTT-bias first recognized by Floyd et al, SIGCOMM 1991

Simple solution was proposed, but proved unstable (Henderson et al)

Research community never lost interest in the RTT-fairness problem

FAST

BIC (Improving RTT-unfairness)

Hybla

Motivation & Previous Work

IRTF/ICCRG Meeting

Chicago July 24 2007

beyond rtt fairness
Other Challenges:

Scalability:

TCP NewReno doesn’t scale to Gbps

Friendliness:

Compatible TCP NewReno performance (Co-existence)

Stability:

Lack of Control Theoretical Proofs of Congestion Control Protocols Stability

Libra Algorithm Solutions

Scalability:

The congestion window initially grows proportional to the narrow link capacity

Friendliness:

A parallel Libra goal

Stability:

The congestion window growth slows down as the MAX RTT is approached (avoid heavy congestion in the network)

Beyond RTT-Fairness

IRTF/ICCRG Meeting

Chicago July 24 2007

libra congestion control algorithm
Libra Congestion Control Algorithm

Fairness Control

T0,controls

Thrput Variance

& Convergence

------------

T1 controls

RTT-fairness

  • Derived directly from Fluid model:
    • On a successful transmission:
    • On a packet loss:

Scalability Control

C representsEstimated Capacity

and the PenaltyFunction is

based on queueing delay

IRTF/ICCRG Meeting

Chicago July 24 2007

slide6

Perfect-RTT Fairness

Libra-RTT Fairness

Linear-RTT Fairness

Perfect-RTT Fairness

  • Protocols with “perfect” RTT fairness:
    • But Hybla has narrower stability region
    • Delay based protocols (Vegas, Fast) have co-existence problems with TCP Reno
  • Libra\'s perfect fairness can be tuned by T1

Linear-RTT Fairness

Libra-RTT Fairness

IRTF/ICCRG Meeting

Chicago July 24 2007

dumbbell topology
DumbBell Topology
  • Based on BIC original Test Simulation Suite
    • 4 forward + 4 backward regular long-lived TCP Sack flows
    • 25 TCP flows in both directions, window limited to 64 segments
    • Web traffic in both directions (20-50% of bandwidth)
  • Studied Connections:
    • Short RTT conn: 21 ms
    • Long RTT conn: 119ms

IRTF/ICCRG Meeting

Chicago July 24 2007

slide8

DumbBell Topology Results

Pipe Size Buffer

Small Buffer

  • Studied Flows Achieved Jain Index while competing with cross-traffic
  • TCP Libra obtained the best Jain’s Index
    • specially on small buffers

Jain’s Index

IRTF/ICCRG Meeting

Chicago July 24 2007

parking lot topology
Parking Lot Topology
  • Parking lot topology
    • Flows 1 and 2: 180ms
    • Flows 3 and 4: 90ms
    • Flows 5 through 8: 30ms
    • 2 buffer sizes:
      • 375 and 2250 pkts
  • Jain’s Index

IRTF/ICCRG Meeting

Chicago July 24 2007

parking topology results
Parking Topology Results

50% (even) SACK + 50% (odd) Other TCP

SACK Only Point of View

when Competing with Other Protocols

Same Experiment #1

Different Protocols

Jain Index Computed over Flows 1-4

Same Experiment #1

Different Protocols

Jain Index Computed over Flows 1-8

Buffer Size = Pipe Size = 2250 pkts

Buffer Size = 375 pkts

  • TCP Libra obtained optimal RTT-Fairness among flows utilizing the same number of congested queues
  • FAST shows unfriendliness
    • by reducing flows 2 and 4
  • BIC couldn’t reach good utilization
  • Libra balancea:
    • RTT-FairnessandFriendliness
    • Improved RTT-Fairness of SACK !!

IRTF/ICCRG Meeting

Chicago July 24 2007

conclusion
The main contribution of this work is to propose a stable solution to an old problem RTT-fairness (Floyd et al 1991)

A complete proof of the stability bound for a simple case may be found in recent publication at IFIP/Networking 2007

TCP Libra proves to have an excellent trade-off between fairness, efficiency and friendliness

http://www.tcplibra.org/

Conclusion

IRTF/ICCRG Meeting

Chicago July 24 2007

recent congestion control research at ucla2

Recent Congestion Control Research at UCLA

TCP Evaluation Suite

Authors: Hideyuki Shimonishi*, Cesar Marcondes**, M.Y. Sanadidi**, Mario Gerla**, Padmanabhan Vasu**

NEC Japan*

NRL – UCLA**

Presenter:

Cesar Marcondes

PhD Candidate CS/UCLA

Chicago, July 24 2007

IRTF/ICCRG Meeting

motivation
TCP NewReno well-known doesn’t scale to Gbps

Many New Congestion Control Proposed (ARENO, Westwood, BIC, FAST, HTCP, STCP)

However, there is a need of a standard TCP Evaluation Suite for general use

Lack of Meaningful Qualitative Comparison between Proposals

Motivation
  • How do they behave differently
  • Resource fairness vs throughput fairness
  • Efficiency and throughput
  • Fairness and friendliness
  • How do they co-exist with Reno
  • Can we have reasonable scenario for migration ?

IRTF/ICCRG Meeting

Chicago July 24 2007

tcp evaluation suite
TCP Evaluation Suite
  • Reproducible simulation experiments for different set of protocols
    • Pre-configured Environment to be used in Simulation
  • Core Network Size / Link Delay / Workload (Flow Size) / Start time Equal
    • Configurable (Example)
    • Parking Lot Topology
    • 4 core routers w/ 2MB
    • Links delays 15 ms (exponential)
    • Short Lived Flow 1MB/1sec (pareto/exponential)
    • Long Lived Flow 4.7GB/2min (fixed/exponential)

IRTF/ICCRG Meeting

Chicago July 24 2007

qualitative tcp evaluation comparison
After several simulations using different seeds we have the following results:

RENO + RENO (today)

RENO + HS (2008)

HS + HS (2012)

TReno_iReno+Reno is the throughput of Reno flow i in the first SET where all flow use Reno (RENO+RENO)

Where TReno_iHS+Reno is the throughput of Reno flow i in the second SET in which half of the flows use high-speed protocols RENO + HS).

Where TiHS+HS and TiReno+Reno are the throughput of flow i in the third SET where all flows use high-speed protocols (HS+HS) and the first SET where all flows use Reno (RENO+RENO), respectively

Qualitative TCP Evaluation Comparison

IRTF/ICCRG Meeting

Chicago July 24 2007

qualitative comparison with tcp newreno and congestion window dynamics details
Qualitative Comparison with TCP NewReno and Congestion Window Dynamics Details

Sorted by Flow RTT

Sorted by Link Utilization

Sorted by Number of Hops

Long-Lived Flow 1

Queue Fluctuation (10ms)

Cumulative Packet Losses

IRTF/ICCRG Meeting

Chicago July 24 2007

the suite is available for download
The suite is available for download

http://netlab.cs.ucla.edu/tcpsuite/

Topology

generator

Flow

generator

Workload

generator

New set of metrics allow qualitative comparison with the current state of the network

It is also possible to investigate individual flow dynamics and queues reproducibly

Please submit YOUR scenario

Library for public sharing !

Scenario library

Link A-B BW Delay

Link A-B BW Delay

Tcl scripts for NS2

Log data

Questions, comments, contributions,

to: [email protected],[email protected]

Plotting tools

IRTF/ICCRG Meeting

Chicago July 24 2007

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