Upload
willa-poole
View
29
Download
3
Embed Size (px)
DESCRIPTION
TCP Networks Stabilized by Buffer-Based AQMs Huaizhong Han, C. V. Hollot, Yossi Chait (University of Massachusetts at Amherst), Vishal Misra (Columbia University) Thanks to NSF Grant #ANI-0125979. Presented by H. Han ECE at UMass-Amherst. router. Buffer-based AQM. Internet. Background (I). - PowerPoint PPT Presentation
Citation preview
04/19/23 INFOCOM'04
TCP Networks Stabilized by Buffer-Based AQMs
Huaizhong Han, C. V. Hollot, Yossi Chait (University of Massachusetts at Amherst), Vishal Misra (Columbia
University)
Thanks to NSF Grant #ANI-0125979
Presented by H. Han
ECE at UMass-Amherst
04/19/23 INFOCOM'04
Internet
TCP
TCP
router
Buffer-based AQM
Background (I)
04/19/23 INFOCOM'04
AQM
tcpsources
x
q
p
bwddelay
aqmrouter
fwddelay
x
p
AQM
q
u
Background (II)
lpflpf
04/19/23 INFOCOM'04
Network Congestion
TCP
TCP
congested
links
04/19/23 INFOCOM'04
Linearized Model of Network Congestion
lpf
x
R(s)
RT(-s)pu
aqmrouters
tcpsources
ijsijR e
04/19/23 INFOCOM'04
R(s)
RT(-s)
AQMrouters
F(s) bufferbased
1( )( )D s sI
G(s)ratebased
0 1( ) ( ) ( ) ( ) ( )( )TL s R s F s R s D s sI
Linear Stability
TCP
04/19/23 INFOCOM'04
Generalized Nyquist Theorem
[ ( )]iλ L jω
-1+j0
Re
not encircling -1+j0
linear closed-loop stability
: [ ( )]ii λ L jω
Im
04/19/23 INFOCOM'04
Main Result (I)
2{ ,1} { ( ) ( )}[ ( )] : ( )
{ ( )}R k
i
Co Co d j f jL j S
Co g j
2
1minRx
Rx
xroutinggain
04/19/23 INFOCOM'04
[ ( )]L j
( )S
Illustration(two-source, two links)
04/19/23 INFOCOM'04
Main Result (II)
linear closed-loop stability
-1+j0
[ ( )]i L j
( )SRe
Im
04/19/23 INFOCOM'04
Impact of Routing Matrix R (I)
big large stability margins
stability margins
R
R
σ
σ small small
2{ ,1} { ( ) ( )}[ ( )]
{ ( )}R k
i
Co Co d j f jL j
Co g j
04/19/23 INFOCOM'04
Impact of Routing Matrix R (II)
2
1 1 0 0 0 0
(0) 0 0 1 1 0 0 ; 2
0 0 0 0 1 1RR
2
0 1 0 1 1 1
(0) 0 1 1 1 1 1 ; 0.37
1 0 1 1 1 1RR
04/19/23 INFOCOM'04
0 50 100 150 200 250 300 3500
100
200
300
400
500R
bigR
small
Network Simulation
04/19/23 INFOCOM'04
Uncertainty in Routing Gain
maxint[ / ]
min
RA
RA
m n m
m = # of tcp sourcesn = # of congested liksA = binary full rank matrices
measure of
routing gain
uncertainty
robustness decreases with # of tcp sources and congested links
04/19/23 INFOCOM'04
Contribution of Work
• Stability condition for buffer-based AQMs– RED, REM, PI …
• Connection between routing and stability
• “Gain of Routing” as robustness measure -expressed in terms of numbers of sources and links.
04/19/23 INFOCOM'04
Future Research
• In practice how many congested links do sourcesencounter?
• Do present routing algorithms result in specific pattern of routing matrices R(0)? For example: how does shortest-path routing impact congestion control?