recent congestion control research at ucla presenter: cesar marcondes phd candidate cs/ucla chicago,...

Recent Congestion Control Research at UCLA

Presenter: Cesar MarcondesPhD Candidate CS/UCLAChicago, July 24 2007IRTF/ICCRG Meeting

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**TCP Evaluation Suite

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

Padmanabhan Vasu**NEC Japan*

NRL – 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**

IRTF/ICCRG MeetingChicago July 24 2007

Motivation & Previous WorkMotivation & Previous Work

RTT fairness: TCP sessions share

same bottleneck => same bandwidth

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

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

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


Beyond RTT-FairnessBeyond 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

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)

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)


Derived directly from Fluid model:On a successful transmission:

On a packet loss:

Derived directly from Fluid model:On a successful transmission:

On a packet loss:

Libra Congestion Control Algorithm Libra Congestion Control Algorithm

€

w(n +1) = w(n) +1

w(n)α n

Tn2

To + Tn

€

w(n +1) = w(n) −w(n)

2

T1

(To + Tn )

MAX

n

Ceknϕϕ

α−

= 1

Fairness Control T0, controls

Thrput Variance& Convergence

------------T1 controls

RTT-fairness

Scalability Control C represents Estimated Capacity

and the Penalty Function is based on queueing delay


Linear-RTT Fairness Perfect-RTT Fairness Libra-RTT Fairness

Protocols with “perfect” RTT fairness:

But Hybla has narrower stability regionDelay based protocols (Vegas, Fast) have co-existence problems with TCP Reno

Libra's perfect fairness can be tuned by T1

Linear-RTT Fairness

Perfect-RTT Fairness

Libra-RTT Fairness


DumbBell TopologyDumbBell 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

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


DumbBell Topology ResultsDumbBell Topology Results

Studied Flows Achieved Jain Index while competing with cross-traffic

TCP Libra obtained the best Jain’s Index specially on small buffers

Studied Flows Achieved Jain Index while competing with cross-traffic

TCP Libra obtained the best Jain’s Index specially on small buffers

Small Buffer Pipe Size Buffer

Jain’s Index


Parking Lot TopologyParking 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

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


Parking Topology ResultsParking Topology Results

Same Experiment #1Different ProtocolsJain Index Computed over Flows 1-4

Same Experiment #1Different ProtocolsJain Index Computed over Flows 1-8

Buffer Size = 375 pkts Buffer Size = Pipe Size = 2250 pkts

• TCP Libra obtained optimal RTT-Fairness among flows utilizing the

same number of congested queues

50% (even) SACK + 50% (odd) Other TCPSACK Only Point of View when Competing with Other Protocols

FAST shows unfriendlinessby reducing flows 2 and 4

BIC couldn’t reach good utilization Libra balancea:

RTT-Fairness and FriendlinessImproved RTT-Fairness of SACK !!


ConclusionConclusion 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

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/

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

http://www.tcplibra.org/



TCP Evaluation SuiteAuthors: Hideyuki Shimonishi*, Cesar Marcondes**, M.Y.

Sanadidi**, Mario Gerla**, Padmanabhan Vasu**NEC Japan*

NRL – UCLA**


MotivationMotivation 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

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

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 ?


TCP Evaluation SuiteTCP 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)

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)

Topology-generator Flow-generator Workload-generator

Link A-B BW DelaySrc A èDestB

Time : size…

Time : size…

Time : size…

Time, sizeTime, sizeÅEÅEÅE

Client-server, peer-to-peer, etc…

Simulation run 2

Compare

Heavy-tail, long-live, real trace data, etc…

Random, tree, parking-lot, etc…

Reno+Reno Reno+HS HS+HSReno+Reno Reno+HS HS+HS

SrcA èDestB

SrcA èDestBSrcA è

DestB

SrcA èDestB

SrcA èDestBLink A-B BW DelayLink A-B BW Delay

Simulation run 3Simulation run 1


Qualitative TCP Evaluation Comparison

Qualitative TCP Evaluation Comparison

After several simulations using different seeds we have the following results: RENO + RENO (today) RENO + HS (2008) HS + HS (2012)

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 Ti

Reno+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

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 Ti

Reno+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 Comparison with TCP NewReno and Congestion Window

Dynamics Details

Qualitative Comparison with TCP NewReno and Congestion Window

Dynamics Details

Sorted by Link Utilization Sorted by Number of Hops Sorted by Flow RTT

Long-Lived Flow 1 Queue Fluctuation (10ms) Cumulative Packet Losses


The suite is available for download

The suite is available for download

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

Flowgenerator

Workloadgenerator

Link A-B BW DelayLink A-B BW DelayScenario library

Tcl scripts for NS2

Log data

Plotting tools

New set of metrics allow qualitative comparison with the current state of the networkIt is also possible to investigate individual flow dynamics and queues reproducibly

Please submit YOUR scenario Library for public sharing !Questions, comments, contributions,to: [email protected],[email protected]

mailto:[email protected]











recent congestion control research at ucla presenter: cesar marcondes phd candidate cs/ucla chicago,...

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