With Extra Bandwidth and Time for Adjustment

TCP is Competitive

J. Edmonds, S. Datta, and P. Dymond

• Email• Web • Telnet

Bytes on the Internet

TCPOther

TCP (Transport Control Protocol)AIMD (Additive Increase, Multiplicative Decrease)

•Arrival time •File Size

Input: Set of Sender/Jobs

•Many Packets Data Flow

Adjustments

Bottleneck Capacity and Adjustments

B

b ,t

b ,t B

(not buffer or time delay)

Time

A=1 c=½

b ,t

Additive increase

Multiplicative decrease

TCP (Transport Control Protocol)AIMD (Additive Increase, Multiplicative Decrease)

Evaluating TCP

•Fair to all Users

•Good observed performance •Simulation of approximate models•Few theoretical results

•[KKPS] 20 Questions to “guess” allocation

•[CJ] Single-bottleneck:TCP fair •[F] Multi-bottleneck: TCP not fair

(completion - arrival )AVG• “User Perceived Latency” or “Flow Time”

•Throughput & packet loss rate

User Perceived LatencyFlow Time

(c - a )AVG

J = { , , , , , , … , , }

Bad(J)Good(J) (c - a )AVG= n Long

(n-1) + Long n

Good(J) =

…… ca

Bad(J) = … ca

Comparison with other Schedulers

BTCP

BEQUI

ShortestRemainingWork First

B

•[CJ] TCP EQUI

•Optimal

Knowledge of Scheduler

Non-Clairvoyant: ?

Online: ?Future

Distributed: ?

Optimal: All KnowingAll Powerful

TCP

Not Competitive

Competitive

Previous Results(Batch)

EQUI(J)OPT(J) 2[MPT]

[ECBD] 3.73

a

Previous Results(Lower Bounds)

EQUI(J)OPT(J) (n)[MPT]

NonClair(J)OPT(J) (n½)

aa aa a

Previous Results (Upper Bounds)

BAL1+(J)OPT1(J) O(1/)[KP]

[E] EQUI2+(J)OPT1(J) O(1/)

[EP] BROADCAST4+(J)OPT1(J) O(1/)

O(1)OPT(J)TCP(J)

New Results

OPT1(J)TCPO(1)(J)

AdjAdj Adj

q q

OPT1(J)TCPO(1)(J) - Adj

Proof Sketch

[E] EQUI2+(J)OPT1(J) O(1)

Reduction

TCP EQUI

[CJ] global measure

BTCP

BEQUI

•TCP EQUI

New: Job by job comparison

Proof Sketch

b ,t

Unadjusted Adjusted

Proof Sketch

Time

A=1 c=½

UnadjustedAdjusted

b ,t

at ,b ,t

After q ,TCP (1-cq) EQUI b ,t

Proof Sketch

c=½b ,tTCP

EQUI b ,t

at ,b ,t

After q ,TCP (1-cq) EQUI b ,t

TCPO(1) b ,t

b ,tTCPO(1) EQUI b ,t

Proof Sketch

EQUI

Proof Sketch

EQUI

O(1)OPT(J)TCP(J)

New Results

OPT1(J)TCPO(1)(J)

OPT1(J) + AdjTCPO(1)(J)

Proof Sketch

O(1)OPT1(J)TCPO(1)(J) EQUI2+(J’)

OPT1(J’ )Adj+ OPT1(J’ )+

J

TCPO(1) b ,t

EQUI b ,t

J’Less

Proof Sketch

O(1)OPT1(J)TCPO(1)(J) EQUI2+(J’)

OPT1(J’ )Adj+ OPT1(J’ )+

J

TCPO(1) b ,t

EQUI b ,t

J’Less

Less

Proof SketchTCPO(1) b ,t

EQUI b ,t

AdjAdj Adj

q q

Less Adj

Less Less Less

Proof Sketch

EQUI

Less

Adjq

Less Adj

Proof Sketch

O(1)OPT1(J)TCPO(1)(J) EQUI2+(J’)

OPT1(J’ )Adj+ OPT1(J’ )+

J

TCPO(1) b ,t

EQUI b ,t

J’Less

Less

Proof Sketch

O(1)OPT1(J)TCPO(1)(J) EQUI2+(J’)

OPT1(J’ )Adj+ OPT1(J’ )+

J

TCPO(1) b ,t

EQUI b ,t

J’Less

Done

Conclusion

TCP is Competitive

Recent Result