With Extra Bandwidth and Time for Adjustment TCP is Competitive J. Edmonds, S. Datta, and P. Dymond.
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Transcript of With Extra Bandwidth and Time for Adjustment TCP is Competitive J. Edmonds, S. Datta, and P. Dymond.
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