FAST TCP. Speaker: Ray Veune: Room 1026 Date: 25 th October, 2003 Time: 10:00am. Motivation. Demand for ultrascale networking HENP (High Energy and Nuclear Physics) Data volumes of tens of Petabytes (10 15 ) to Exabytes (10 18 ) Require Terabit/sec (10 15 bit/sec or 1000Gbit/sec)
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Router
Dest.
TCP VegasCongestion Avoidance Mechanismα
β
TCP VegasCongestion Avoidance MechanismExpected = WindowSize / BaseRTT
α = 30KB/s, β=60KB/s
α=> 30KBps * 100ms / 1KB = 3
β=> 60KBps * 100ms / 1KB = 6
Rlr = {
lr
Stability of TCP VegasNetwork modellr
Stability of TCP VegasNetwork modelx1(t)
p1(t)
p3(t)
p4(t)
x2(t)
p2(t)
l
r
lr
Stability of TCP VegasNetwork model + = Tr, l L
pl (t) = ( yl ( t ) –cl ) / clif pl (t) > 0
( yl ( t ) –cl ) / cl )+if pl (t) = 0
xr (t) = 1/Tr2(t) sgn( 1 –xr(t)qr(t) / rdr )
Tr (t) = dr + qr( t )
Where sgn(z) = 1 if z > 0, -1 if z < 0 and 0 if z = 0
(z)+ = max { 0 , z }
xr* qr*= r dr
maxr xr*Tr sinc (ň / xr*Tr ) < / Mk02
qr* /Tr
minr > Mk02
ň
.
sinc ( )
qr*
Tr
Stability of TCP Vegas Corollary 22 + 2a2
cd < ( - 1 ) N
2 + a2
Stabilized Vegaswhere = tan-1( (2)/(1-) )
( a>0, (0,1) ) such that RHS can be larger for better stability of the original Vegas cd < (/2 – 1) N