Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

11

IAST

ED P

DCN

200

4 Tu

tori

al:

IAST

ED P

DCN

200

4 Tu

tori

al:

Shap

ing

the

Futu

re o

fSh

apin

g th

e Fu

ture

of

Inte

rnet

Con

gest

ion

Cont

rol

Inte

rnet

Con

gest

ion

Cont

rol

Mic

hael

Wel

zl

Mic

hael

Wel

zl

http

://w

ww

.wel

zl.a

tht

tp:/

/ww

w.w

elzl

.at

Dis

trib

uted

and

Par

alle

l Sys

tem

s G

roup

Dis

trib

uted

and

Par

alle

l Sys

tem

s G

roup

Inst

itut

e of

Com

pute

r Sc

ienc

eIn

stit

ute

of C

ompu

ter

Scie

nce

Uni

vers

ity

Uni

vers

ity

ofofIn

nsbr

uck

Inns

bruc

k

http://www.welzl.at/

Uni

Inn

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ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

22

Out

line

Out

line

1.Co

nges

tion

Con

trol

: a

quic

k in

trod

ucti

on

2.Pr

oble

ms

3.So

me

prop

osed

enh

ance

men

ts

4.H

ow t

o de

sign

you

r ow

n co

nges

tion

con

trol

mec

hani

sm

Rese

arch

pro

cedu

re:

1.ge

t to

kno

w t

he f

ield

2.id

enti

fy p

robl

ems

3.lo

ok a

t w

hat

othe

rs

have

don

e

4.co

me

up w

ith

your

ow

n so

luti

ons

Uni

Inn

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ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

33

Cong

esti

on C

ontr

olCo

nges

tion

Con

trol

A qu

ick

intr

oduc

tion

Uni

Inn

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ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

44

Prob

lem

sta

tem

ent

Prob

lem

sta

tem

ent

•Ef

fici

ent

tran

smis

sion

of

data

str

eam

s ac

ross

the

Inte

rnet

–va

riou

s so

urce

s, v

ario

us d

esti

nati

ons,

var

ious

typ

es o

f st

ream

s

•W

hat

is „

effi

cien

t“?

–te

rms:

late

ncy,

end

2end

del

ay,

jitt

er,

band

wid

th(n

omin

al/a

vaila

ble/

bott

lene

ck -

), t

hrou

ghpu

t, g

oodp

ut,

loss

rat

io,

..–

goal

s: h

igh

thro

ughp

ut(b

its

/ se

cond

), lo

wde

lay,

jit

ter,

loss

rat

io

•N

ote:

Inte

rnet

= T

CP/I

P ba

sed

wor

ld-w

ide

netw

ork

–no

ass

umpt

ions

abo

ut lo

wer

laye

rs!

–ig

nore

CSM

A/CD

, CS

MA/

CA,

toke

n ri

ng,

base

band

enc

odin

g, f

ram

e ov

erhe

ad,

swit

ches

, et

c. e

tc.

!

typically bit/s

at this level!

Uni

Inn

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ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

55

A s

impl

eA

sim

ple

rout

er m

odel

rout

er m

odel Q

ueue

1

Que

ue 2

Swit

chin

gFa

bric

In 1

Out

1In

2O

ut 2

In 3 •

Swit

chin

g fa

bric

forw

ards

a pa

cket

(de

st.

addr

.)if

nosp

ecia

l tre

atm

ent

nece

ssar

y: f

ast

path

(har

dwar

e)

•Q

ueue

sgr

ow w

hen

traf

fic

burs

ts a

rriv

e•

low

del

ay=

smal

l que

ues,

low

jit

ter

= m

inor

que

ue f

luct

uati

ons

•Pa

cket

s ar

e dr

oppe

dw

hen

queu

es o

verf

low

(“D

ropT

ailq

ueue

ing“

)•

low

loss

rat

io=

smal

l que

ues

Uni

Inn

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ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

66

The

cong

esti

on p

robl

emTh

e co

nges

tion

pro

blem

•Co

nges

tion

cont

rol n

eces

sary

•ad

ding

fast

link

sdo

es n

othe

lp!

S1D

1

D2

S2

100

kb/s

1000

kb/s

100

kb/s

10kb

/s

110

kb/s

Que

ue

S 1

S 2

Swit

chin

gFa

bric

tota

l thr

ough

put

w/o

cc.

: 20

kb/s

tota

l thr

ough

put

w/

cc.:

110

kb/s

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

77

Cong

esti

on c

olla

pse

Cong

esti

on c

olla

pse

“knee“

“cliff“

Goa

l: o

pera

tion

at

the

“kne

e“

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

88

Inte

rnet

con

gest

ion

cont

rol:

His

tory

Inte

rnet

con

gest

ion

cont

rol:

His

tory

•19

68/6

9:da

wn

ofth

eIn

tern

et•

1986

:fi

rst

cong

esti

onco

llaps

e•

1988

:"C

onge

stio

n Av

oida

nce

and

Cont

rol"

(Jac

obso

n)Co

mbi

ned

cong

esti

on/f

low

con

trol

for

TCP

•G

oal:

stab

ility

-in

equi

libru

m,

no p

acke

tis

sen

t in

to t

he n

etw

ork

unti

lan

old

pack

etle

aves

–ac

k cl

ocki

ng,

“con

serv

atio

nof

pack

ets“

prin

cipl

e–

mad

e po

ssib

le t

hrou

gh w

indo

w b

ased

sto

p+go

-be

havi

our

•Su

perp

osit

ion

ofst

able

syst

ems

=st

able

netw

ork

base

don

TCP

wit

h co

nges

tion

con

trol

=st

able

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

99

TCP

Cong

esti

on

TCP

Cong

esti

on C

ontr

olCo

ntro

l/1

:/1

:Ta

hoe

Taho

e , 1

988

, 19

88

•D

isti

ngui

sh:

–fl

owco

ntro

l:pr

otec

t re

ceiv

erag

ains

t ov

erlo

ad(r

ecei

ver

"gra

nts"

ace

rtai

n am

ount

ofda

ta("

rece

iver

win

dow

") )

–co

nges

tion

con

trol

:pr

otec

t ne

twor

kag

ains

t ov

erlo

ad("

cong

esti

on w

indo

w"

(cw

nd)

limit

sth

e ra

te:

min

(cw

nd,r

wnd

) us

ed!

)

•Fl

ow/C

onge

stio

nCo

ntro

l com

bine

din

TCP

.Se

vera

l alg

orit

hms:

•(w

indo

w u

nit:

SM

SS=

Send

er M

axim

um S

egm

ent

Size

, us

ually

adju

sted

to

Path

MTU

; in

it c

wnd

=

ssth

resh

–Co

nges

tion

Avoi

danc

e:ea

chRT

T,in

crea

se c

wnd

by

SMSS

*SM

SS/c

wnd

(lin

ear

grow

th -

"add

itiv

e in

crea

se")

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1010

TCP

Cong

esti

onTC

P Co

nges

tion

Cont

rol

Cont

rol

/2/2

•If

a pa

cket

or a

ck is

lost

(t

imeo

ut,

roug

hly

4*rt

t),

set

cwnd

= 1,

ssth

resh

=cu

rren

t ba

ndw

idth

/ 2

(“m

ulti

plic

ativ

e de

crea

se")

-ex

pone

ntia

lbac

koff

•Se

vera

l tim

ers,

base

don

RT

T; g

ood

esti

mat

ion

is

cruc

ial!

•La

ter

addi

tion

s:(T

CP R

eno,

199

0)Fa

stre

tran

smit

/ fa

stre

cove

ry(n

otif

y se

nder

oflo

ss v

ia d

uplic

ate

acks

)

0123456789

12

34

56

78

910

1112

1314

1516

time

bandwidth

Timeo

ut

ssth

resh Sl

ow Start

Congestion

Avoidance

Uni

Inn

sbru

ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

1111

Use

r 1 A

lloca

tion

x1

Fairn

ess

Line

Effic

ienc

yLi

ne

User 2 Allocation x2

Sta

rting

Poi

nt

AIM

D

Des

irabl

e

Sta

rting

Poi

nt

AIAD

MIM

D Und

erlo

ad

Ove

rload

Use

r 1 A

lloca

tion

x1

Fairn

ess

Line

Effic

ienc

yLi

ne

User 2 Allocation x2

Sta

rting

Poi

nt

AIM

D

Des

irabl

e

Sta

rting

Poi

nt

AIAD

MIM

D Und

erlo

ad

Ove

rload

Back

grou

nd:

AIM

DBa

ckgr

ound

: A

IMD

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1212

Act

ive

Act

ive

Que

ue M

anag

emen

tQ

ueue

Man

agem

ent

•To

day,

TCP

beha

viou

r do

min

ates

the

Inte

rnet

(W

WW

, ..

)

•(s

omew

hat

old)

exa

mpl

e ba

ckbo

ne m

easu

rem

ent:

98%

TCP

traf

fic

•19

93:

Rand

om E

arly

Det

ecti

on("

Dis

card

", "

Dro

p")

(RED

)(n

ow t

hat

end

node

sba

ck o

ffas

pac

kets

are

dro

pped

,dr

oppa

cket

s ea

rlie

rto

avoi

dqu

eue

over

flow

s)

•An

othe

r go

al:

add

rand

omiz

atio

nto

avoi

d tr

affi

c ph

ase

effe

cts!

•Q

avg

= (1

-W

q) x

Qav

g+

Qin

stx

Wq

(Qav

g=

aver

age

occu

panc

y,Q

inst

=in

stan

tane

ous

occu

panc

y,W

q=

wei

ght

-ha

rdto

tun

e,de

term

ines

how

aggr

essi

ve R

EDbe

have

s)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1313

Act

ive

Act

ive

Que

ue M

anag

emen

t /2

Que

ue M

anag

emen

t /2

•Ba

sed

onex

pone

ntia

lly w

eigh

ted

mov

ing

aver

age

(EW

MA)

of

inst

anta

neou

s qu

eue

occu

panc

y=

low

pass

filt

er–

reca

lcul

ated

eve

ryti

me

a pa

cket

arri

ves

•Q

avg

belo

w t

hres

hold

min

_th:

Not

hing

hap

pens

•Q

avg

abov

e th

resh

old

min

_th:

Dro

ppr

obab

ility

ris

es li

near

ly•

Qav

gab

ove

thre

shol

d m

ax_t

h:D

rop

pack

ets

•RE

Dex

pect

sal

lflo

ws

tobe

have

like

TCP

-bu

t is

itfa

ir?

•Va

rian

ts:

drop

from

fron

t, d

rop

base

don

inst

anta

neou

s qu

eue

occu

panc

y, d

rop

arbi

trar

y pa

cket

s, d

rop

base

don

prio

riti

es..

.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1414

Expl

icit

Expl

icit

Cong

esti

onCo

nges

tion

Not

ific

atio

nN

otif

icat

ion

(ECN

)(E

CN)

•19

99:

Expl

icit

Cong

esti

onN

otif

icat

ion

(ECN

)In

stea

dof

drop

ping

,se

ta

bit

•En

d sy

stem

sar

e ex

pect

edto

act

as if

pack

et w

asdr

oppe

d⇒

actu

al c

omm

unic

atio

n be

twee

nen

dno

des

and

the

netw

ork!

•AT

M a

nd F

ram

eRe

lay:

not

only

ECN

but

also

BEC

N

•In

tern

et B

ECN

:of

ten

prop

osed

and

regu

larl

y di

scus

sed

(ICM

P SQ

),bu

t ve

ry u

nlik

ely

-se

vera

l rea

sons

•Ve

ry p

opul

ar a

mon

g re

sear

cher

s -

lots

of

idea

s to

exp

loit

the

bit

!

•EC

Nca

nnot

tot

ally

rep

lace

loss

mea

sure

men

ts!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1515

Prob

lem

sPr

oble

ms

( =

pote

ntia

l res

earc

h to

pics

)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1616

TCP

TCP

in h

eter

ogen

eous

env

iron

men

tsin

het

erog

eneo

us e

nvir

onm

ents

•TC

P ov

er n

oisy

link

s: p

robl

ems

wit

h „p

acke

t lo

ss =

con

gest

ion“

–w

asba

did

eain

tim

esof

erro

r-pr

one

netw

orks

–se

ems

reas

onab

lein

tim

esof

fibr

e ne

twor

ks–

real

ly b

ad f

orw

irel

ess

links

!

•TC

Pov

er“l

ong

fat

pipe

s“:

larg

e ba

ndw

idth

*del

ay p

rodu

ct–

long

tim

e to

reac

h eq

uilib

rium

, M

D =

prob

lem

atic

!

•TC

P in

hig

hly

asym

met

ric

netw

orks

:(e

.g.

dire

ct s

atel

lite

last

mile

)–

inco

min

g th

roug

hput

(hi

gh c

apac

ity

link)

lim

ited

by

rate

of

outg

oing

ACK

s(„

ACK

com

pres

sion

“)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1717

Fair

ness

Fair

ness

•AT

M A

BR:

Max

-Min

-fai

rnes

s–

“A (

..)

allo

cati

onof

rate

s is

max

-min

fai

rif

fan

incr

ease

ofan

yra

te (

..)

mus

t be

atth

e co

stof

ade

crea

seof

som

e al

read

y sm

alle

rra

te.“

–O

nere

sour

ce:

mat

hem

atic

al d

efin

itio

n sa

tisf

ies

"gen

eral

"un

ders

tand

ing

offa

irne

ss-

reso

urce

is d

ivid

ed e

qual

ly a

mon

g co

mpe

tito

rs–

Usu

ally

requ

ires

kno

wle

dge

offl

ows

inro

uter

s(s

wit

ches

) -

scal

abili

ty p

robl

em!

•In

tern

et:

–TC

P do

min

ant,

but

does

not

sat

isfy

Max

-Min

-fai

rnes

s cr

iter

ion!

–Ac

k-cl

ocke

d-

flow

s w

ith

shor

ter

RTT

reac

t so

oner

(slo

wst

art,

..)

and

achi

eve

bett

er r

esul

ts–

Ther

efor

e, In

tern

etde

fini

tion

offa

irne

ss:

TCP-

frie

ndlin

ess

"Afl

ow is

TCP-

com

pati

ble

(TCP

-fri

endl

y)if

, in

stea

dy s

tate

,it

use

sno

mor

e ba

ndw

idth

tha

na

conf

orm

ant

TCP

runn

ing

unde

r co

mpa

rabl

e co

ndit

ions

."

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1818

Issu

es w

ith

TCP

Issu

es w

ith

TCP

-- fri

endl

ines

sfr

iend

lines

s

•TC

P re

gula

rly

incr

ease

s th

e qu

eue

leng

than

d ca

uses

loss

⇒de

tect

con

gest

ion

whe

n it

is a

lrea

dy (

ECN

: al

mos

t) t

oo la

te!

–po

ssib

le t

o ha

vem

ore

thro

ughp

ut w

ith

smal

ler

queu

es a

nd le

ss lo

ss..

. bu

t: e

xcee

d ra

te o

f TC

P un

der

sim

ilar

cond

itio

ns ⇒

not

TCP-

frie

ndly

!

•W

hat

if I

send

mor

e th

an T

CP i

n th

e ab

senc

eof

com

peti

ng T

CP‘s

?–

can

such

a m

echa

nism

exi

st?

–ye

s! T

CP it

self

, w

ith

max

. w

indo

w s

ize

= ba

ndw

idth

* R

TT–

Doe

s th

is m

ean

that

TC

P is

not

TCP

-fri

endl

y?

•D

etai

ls m

issi

ng f

rom

the

def

init

ion:

–pa

ram

eter

s +

vers

ion

of „

conf

orm

ant

TCP“

–du

rati

on!

shor

t TC

P fl

ows

are

diff

eren

t th

an lo

ng o

nes

•TC

P-fr

iend

lines

s =

com

pati

bilit

y of

new

mec

hani

sms

wit

h ol

d m

echa

nism

–th

ere

was

res

earc

h si

nce

the

80‘s

! e.

g. n

ew k

now

ledg

e ab

out

netw

ork

mea

sure

men

ts

•TC

P ra

te d

epen

ds o

n RT

T -

how

doe

s th

is r

elat

e to

„fa

irne

ss“?

Does TCP-friendliness

hinder research?

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

1919

Prop

orti

onal

Fai

rnes

sPr

opor

tion

al F

airn

ess

Prop

orti

onal

fair

ness

:“A

nal

loca

tion

ofra

tes

xis

pro

port

iona

llyfa

irif

f,fo

r an

y ot

her

(..)

allo

cati

on

y,w

e ha

ve:

“

(rou

ghly

appr

oxim

ated

by

AIM

D!)

01

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2020

Cong

esti

on p

rici

ngCo

nges

tion

pri

cing

•Ba

sic

idea

:hi

gher

sen

ding

rat

e =

mor

e co

nges

tion

= h

ighe

r pr

ice

–Id

ea:

char

ge m

ore

whe

n EC

Nfl

ag is

set

•„S

mar

t“ M

arke

tid

ea:

–ea

ch p

acke

t bi

ds f

or c

apac

ity

–ou

t of

nbi

ds,

mhi

ghes

t bi

ds c

an b

e ac

cept

ed–

pric

e: „

mar

gina

l cos

t“ (

high

est

bid

of u

nacc

epte

d pa

cket

s)⇒

lead

s to

mar

ket

equi

libri

um

•„S

mar

t“ M

arke

t no

t pr

acti

cal (

bidd

ing

per

pack

et),

but

sho

ws:

–ba

lanc

e of

dem

and

and

supp

ly le

ads

to m

arke

t eq

uilib

rium

–st

able

sys

tem

jus

t ba

sed

on e

cono

mic

s su

ffic

es f

or c

onge

stio

n co

ntro

l

•Pr

oble

m:

link

cann

ot k

now

bid

s in

adv

ance

⇒no

QoS

guar

ante

es

Uni

Inn

sbru

ckU

ni I

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ruck

Info

rmat

ik

Info

rmat

ik --

2121

End2

end

real

End2

end

real

-- tim

eti

me

data

tra

nsfe

rda

ta t

rans

fer

•As

sum

ptio

n: n

osp

ecia

l ser

vice

ava

ilabl

eat

appl

icat

ion

leve

l–

(Def

init

ion

of In

tern

et "

real

-tim

e"so

fter

than

usu

al)

•D

iffe

rent

requ

irem

ents

:–

relia

ble

serv

ice

may

not

be

need

ed(n

ore

tran

smis

sion

)–

Tim

ely

tran

smis

sion

impo

rtan

t

–D

iffe

rent

trea

tmen

t:–

nore

tran

smis

sion

/ w

aiti

ng f

or A

CKs

–no

slid

ing

win

dow

(sto

p +

go b

ehav

iour

not

sui

tabl

e)–

but:

–so

me

kind

offl

ow c

ontr

olst

illne

eded

–sy

nchr

oniz

atio

n ne

cess

ary

–of

ten:

Mul

tica

st

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2222

Mul

tim

edia

ada

ptat

ion

Mul

tim

edia

ada

ptat

ion

•M

ista

ke:

–ad

apta

tion

sch

emes

ass

ume

arbi

trar

y da

ta s

trea

m s

cala

bilit

y

•Pr

oble

m:

–D

ata

stre

ams

show

flu

ctua

tion

s (e

xam

ple:

MPE

G I-

, B-

, P-

fram

es)

•So

luti

on:

–Sp

ecia

l CBR

des

ign

for

com

mun

icat

ion

-H

.261

des

igne

d fo

r IS

DN

–no

t al

way

s fe

asib

le

•Pr

oble

m:

–co

mpr

essi

on u

sual

ly n

ot d

eter

min

isti

c -

size

dep

ends

on

cont

ent!

–re

al-l

ife

dist

ance

lear

ning

exa

mpl

e:40

kbps

eno

ugh

for

stre

amin

g vi

deo

(Sm

artb

oard

) +

audi

o (s

peec

h),

but

spee

ch s

uffe

rs d

ram

atic

ally

if t

each

er v

isib

le

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2323

Cong

esti

on C

ontr

ol a

nd Q

ualit

y of

Ser

vice

Cong

esti

on C

ontr

ol a

nd Q

ualit

y of

Ser

vice

•Q

ualit

y of

Ser

vice

(Q

oS):

prov

ide

diff

eren

tiat

ed q

ualit

y ba

sed

on $

$$

•Q

uest

ions

:–

is a

flu

id lo

w-q

ualit

y vi

deo

bett

er t

han

a bu

ckin

g hi

gh-q

ualit

y vi

deo?

–an

d w

hat

abou

t au

dio?

•Sc

alab

le Q

oS =

no

per-

flow

gua

rant

ees

–st

anda

rd a

rchi

tect

ure:

Dif

fere

ntia

ted

Serv

ices

(D

iffS

erv)

plac

es u

sers

in f

low

agg

rega

tes

–co

nges

tion

con

trol

sti

ll ne

cess

ary

wit

hin

an a

ggre

gate

⇒pe

r-fl

ow Q

oS d

epen

ds o

n co

nges

tion

con

trol

mec

hani

sm!

–H

ow d

oes

a co

nges

tion

con

trol

mec

hani

sm in

tera

ct w

ith

QoS

ele

men

ts?

e.g.

TCP

kno

wn

to b

e a

bad

mat

ch f

or t

oken

buc

ket

...modest QoS with adaptive

multimedia? -

still unresolved!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2424

Spec

ial t

ypes

of

traf

fic

Spec

ial t

ypes

of

traf

fic

•G

rid:

pre

dict

able

tra

ffic

pat

tern

–Th

is is

tot

ally

new

to

the

Inte

rnet

!•

Web

: us

ers

crea

te t

raff

ic•

FTP

dow

nloa

d: s

tart

s ..

. en

ds•

Stre

amin

g vi

deo:

eit

her

CBR

or d

epen

ds o

n co

nten

t! (

head

mov

emen

t, .

.)

•Sp

ecia

l req

uire

men

ts a

nd p

rope

rtie

s–

may

req

uire

del

ay b

ound

s or

min

imum

ban

dwid

th–

mix

ture

of

spor

adic

(RP

C ty

pe)

mes

sage

s an

d bu

lk d

ata

tran

sfer

•Re

late

d: s

igna

ling

traf

fic

–us

ually

not

a la

rge

amou

nt o

f da

ta–

to d

ate,

no

seri

ous

effo

rts

for

tailo

red

cong

esti

on c

ontr

ol(S

CTP

= tr

ansp

ort

prot

ocol

des

igne

d fo

r si

gnal

ing;

con

gest

ion

cont

rol=

si

mila

r to

TCP

)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2525

Som

e re

ason

s fo

r TC

P st

abili

tySo

me

reas

ons

for

TCP

stab

ility

“Con

gest

ion

Avoi

danc

e an

d Co

ntro

l“,

Van

Jaco

bson

, SI

GCO

MM

‘88:

•Ex

pone

ntia

l bac

koff

:“F

or a

tra

nspo

rt e

ndpo

int

embe

dded

in a

net

wor

k of

unk

now

n to

polo

gy a

nd w

ith

an u

nkno

wn,

unk

now

able

and

con

stan

tly

chan

ging

popu

lati

on o

f co

mpe

ting

con

vers

atio

ns,

only

one

sch

eme

has

any

hope

of

wor

king

-ex

pone

ntia

l bac

koff

-bu

t a

proo

f of

thi

s is

bey

ond

the

scop

e of

thi

s pa

per.

“

•Co

nser

vati

on o

f pa

cket

s:“T

he p

hysi

cs o

f fl

ow p

redi

cts

that

sys

tem

s w

ith

this

pro

pert

y sh

ould

be

rob

ust

in t

he f

ace

of c

onge

stio

n.“

•Ad

diti

ve In

crea

se,

Mul

tipl

icat

ive

Dec

reas

e:N

ot e

xplic

itel

y ci

ted

as a

sta

bilit

y re

ason

in t

he p

aper

!–

...b

ut in

100

0‘s

of o

ther

pap

ers!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2626

“Pro

ofs“

of

TCP

stab

ility

“Pro

ofs“

of

TCP

stab

ility

•AI

MD

:Ch

iu/J

ain:

dia

gram

+ a

lgeb

raic

pro

of o

f ho

mog

eneo

us R

TT c

ase

•st

eady

-sta

te T

CP m

odel

: w

indo

w s

ize

~ 1/

sqrt

(p)

(p =

pac

ket

loss

)

•Jo

hari

/Tan

, M

asso

ulié

, ..

:–

loca

lsta

bilit

y, n

egle

ct d

etai

ls o

f TC

P be

havi

our

(flu

id f

low

mod

el,

..)

–as

sum

ptio

n:“q

ueue

ing

dela

ys w

ill e

vent

ually

bec

ome

smal

l rel

ativ

e to

pro

paga

tion

del

ays“

•St

even

Low

:–

Dua

lity

mod

el (

base

d on

uti

lity

func

tion

/ F

. Ke

lly,

..):

Stab

ility

dep

ends

on

dela

y, c

apac

ity,

load

and

AQ

M !

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2727

Uni

cast

/ B

road

cast

/ (

over

lay)

Mul

tica

stU

nica

st /

Bro

adca

st /

(ov

erla

y) M

ulti

cast

1 Sender

2 Receivers

SRR

Unicast

SRR

Broadcast

SRR

Overlay Multicast

SRR

IP Multicast

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2828

Mul

tica

st is

sues

Mul

tica

st is

sues

•Re

quir

ed f

or a

pplic

atio

ns w

ith

mul

tipl

e re

ceiv

ers

only

–vi

deo

conf

eren

ces,

rea

l-ti

me

data

str

eam

tra

nsm

issi

on,

..⇒

diff

eren

t da

ta s

trea

ms

than

web

sur

fing

, ft

p do

wnl

oads

etc

!

•Is

sues

:–

grou

p m

anag

emen

t•

prot

ocol

req

uire

d to

joi

n /

leav

e gr

oup

dyna

mic

ally

:In

tern

et G

roup

Man

agem

ent

Prot

ocol

(IG

MP)

•st

ate

in r

oute

rs:

hard

/ s

oft

(los

t un

less

ref

resh

ed)?

•w

ho in

itia

tes

/ co

ntro

ls g

roup

mem

bers

hip?

–co

nges

tion

con

trol

•sc

alab

ility

(ACK

impl

osio

n)•

deal

ing

wit

hhe

tero

gene

ity

of r

ecei

ver

grou

ps•

fair

ness

•M

ulti

cast

con

gest

ion

cont

rol m

echa

nism

cla

ssif

icat

ion:

–se

nder

-vs

. re

ceiv

er-b

ased

, si

ngle

-rat

e vs

. m

ulti

-rat

e (l

ayer

ed),

–re

liabl

e vs

. un

relia

ble,

end

-to-

end

vs.

netw

ork-

supp

orte

d

depends on

content!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

2929

Som

e pr

opos

ed e

nhan

cem

ents

Som

e pr

opos

ed e

nhan

cem

ents

Rese

arch

by

othe

rs

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3030

Inte

rnet

Inte

rnet

traf

fic

char

acte

rist

ics

traf

fic

char

acte

rist

ics

•M

RTG

trac

e(b

ased

on S

NM

P,ac

cess

ing

traf

fic

coun

ters

in M

IB)

http

://w

ww

.switc

h.ch

/lan/

stat

/pee

rings

/link

eune

t.htm

l, 11

. 10.

99,

13:

05

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3131

Inte

rnet

Inte

rnet

traf

fic

char

acte

rist

ics

traf

fic

char

acte

rist

ics

/2/2

•Tr

adit

iona

ltra

ffic

mod

ellin

g:qu

euin

g th

eory

noti

on:

traf

fic

follo

ws

pois

son

dist

ribu

tion

•In

tern

ettr

affi

c is

bur

sty

-in

tuit

ive

reas

ons:

–TC

Pis

bur

sty

byna

ture

:co

nges

tion

avoi

danc

e,pa

yloa

d vs

.ac

ks…

–AC

Kco

mpr

essi

on c

anca

use

payl

oad

burs

ts d

ueto

ACK

-clo

ckin

g (l

ater

!)

–va

riou

spa

cket

size

s

–Bu

rsts

fro

m q

ueue

s ag

greg

ate

as t

raff

ictr

aver

ses

the

net

–Bu

rsti

ness

ofon

e fl

ow a

ffec

ts o

ther

adap

tive

flow

s

Still true

for user

arrival !

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3232

Inte

rnet

Inte

rnet

traf

fic

char

acte

rist

ics

traf

fic

char

acte

rist

ics

/3/3

•O

verl

appi

ngof

inde

pend

ent

on-o

ffso

urce

s le

ads

todi

stri

buti

on w

ith

heav

y-ta

iled

auto

corr

elat

ion

func

tion

•Lo

ng-r

ange

dep

enda

nce:

"pe

aks

sit

onri

pple

sw

hich

sit

onw

aves

"

•N

o "f

latt

enin

g"to

war

dsa

mea

n as

you

zoom

out

-sa

me

stru

ctur

es

may

be

foun

dat

dif

fere

nt t

ime

scal

es,

henc

e se

lf s

imila

r

•ch

arac

teri

stic

sm

odel

edw

ith

tim

ese

ries

(fAR

IMA

mod

els)

or w

avel

ets

–M

easu

rem

ent

ofth

e"d

egre

eof

self

sim

ilari

ty":

Hur

stpa

ram

eter

–⇒

mod

elap

prox

imat

ion

invo

lves

Hur

stpa

ram

eter

est

imat

ion

•TC

P kn

own

to p

ropa

gate

bot

tlen

eck

self

-sim

ilari

tyto

end

sys

tem

–po

ssib

ility

: us

e m

odel

to

pred

ict

traf

fic

inst

ead

of g

uess

ing

–qu

esti

on:

scal

abili

ty(w

hat

if e

very

body

doe

s th

is?)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3333

How

How

totobebe

TCP

TCP

-- fri

endl

yfr

iend

ly

•TC

P-fr

iend

lines

s ca

n be

ach

ieve

d by

em

ulat

ing

the

beha

viou

rof

TCP

(or

the

des

ired

par

tsof

it)

•Si

mpl

ifie

dTC

P: A

IMD

(add

itiv

e in

cr. α

,m

ulti

plic

ativ

e de

cr. β)

–0

< α

, 0

< β

< 1

->st

able

and

fair

cong

esti

on c

ontr

ol–α

= 4

x (1

-β^

2) /

3->

TCP

-fri

endl

y co

nges

tion

con

trol

(G

AIM

D)

–α

= 1,

β

= 1/

2->

TCP

•AI

MD

mec

hani

sms

for

mul

tim

edia

app

licat

ions

: RA

P, L

DA+

•D

iffe

rent

appr

oach

es:

–TC

PEm

ulat

ion

At R

ecei

vers

(TE

AR)

TCP

calc

ulat

ions

(cw

nd c

alcu

lati

on,

fast

reco

very

, ..

.)m

oved

tore

ceiv

er,

dono

t ac

k ev

ery

pack

et,

smoo

th s

endi

ngra

te–

Bino

mia

l con

gest

ion

cont

rol:

gene

raliz

atio

n of

GAI

MD

wit

h no

nlin

ear

cont

rol

–CY

RF f

ram

ewor

k:ge

nera

lizat

ion

of b

inom

ial c

onge

stio

n co

ntro

l

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3434

GA

IMD

GA

IMD

cong

esti

on c

ontr

olco

nges

tion

con

trol

Rela

tion

ship

bet

wee

nα

and β

for

TCP-

frie

ndlin

ess:

00,

20,

40,

60,

811,

21,

4

00,

10,

20,

30,

40,

50,

60,

70,

80,

91

beta

alpha

TCP

smoo

ther

mor

eag

gres

sive

+re

spon

sive

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3535

Equa

tion

bas

ed c

onge

stio

n co

ntro

lEq

uati

on b

ased

con

gest

ion

cont

rol

•Ba

sed

on T

CPst

eady

-sta

te r

espo

nse

func

tion

-gi

ves

uppe

r bo

und

for

tran

smis

sion

rate

T (

byte

s/se

c):

)32

1()

833(

322 p

pp

tp

R

sT

RTO

++

=

)32

1()

833(

322 p

pp

tp

R

sT

RTO

++

=

s: p

acke

tsi

zeR:

rtt

t RTO

: TCP

retr

ansm

it t

imeo

utp:

stea

dy-s

tate

loss

eve

ntra

te (t

he d

iffi

cult

par

t!)

•w

ellk

now

n ex

ampl

e: T

FRC

-TC

P-fr

iend

lyra

teco

ntro

l pro

toco

l–

smoo

th s

endi

ngra

te

•Ex

tens

ion:

TFM

CC -

TCP-

frie

ndly

mul

tica

st c

onge

stio

n co

ntro

l

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3636

Not

Not

-- soso-- T

CPTC

P-- f

rien

dly

solu

tion

sfr

iend

ly s

olut

ions

•O

verc

ome

rate

flu

ctua

tion

s:lim

it e

ncod

ings

(e.

g. 2

or

3 qu

alit

ies)

, le

t us

er d

ecid

e

•Cr

oss-

med

ia-a

dapt

atio

n:ch

oose

fro

m v

ideo

, au

dio,

sin

gle

pict

ures

, te

xt(e

.g.

MPE

G7)

•Li

mit

by

bott

lene

ck b

andw

idth

–of

ten:

"la

st m

ile"

-e.

g. R

ealM

edia

–be

tter

: de

term

ine

actu

al b

ottl

enec

k vi

a pa

cket

pai

r ap

proa

ch

•If

wir

eles

s lin

kin

volv

ed:

smal

l pac

kets

, U

DP

Lite

•An

othe

r po

ssib

ility

:se

nd m

ore

(do

FEC)

in r

espo

nse

to p

acke

t lo

ss–

(ver

y ne

twor

k-un

frie

ndly

beh

avio

ur,

but

may

yie

ld le

ss d

ata

loss

)

Network stability: some

adaptation better than none!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3737

Som

e th

ough

tsSo

me

thou

ghts

•H

ow T

CP-f

rien

dly

are

8 w

eb b

row

sers

?–

Cong

esti

on M

anag

er:

cong

esti

on c

ontr

ol f

or a

ll fl

ows

in O

S co

re–

Mul

TCP:

Em

ulat

e m

ulti

ple

TCP‘

s to

pro

vide

dif

fere

ntia

ted

serv

ices

•H

ow T

CP-f

rien

dly

are

shor

t-liv

ed f

low

s? (

web

-tra

ffic

, ..

)

•H

ow t

o co

nvin

ce In

tern

et m

ulti

med

ia a

pp.

prog

ram

mer

s to

im

plem

ent

TCP-

frie

ndly

con

gest

ion

cont

rol?

•So

luti

on:

Dat

agra

m C

onge

stio

n Co

ntro

l Pro

toco

l (D

CCP)

–W

ell-

defi

ned

fram

ewor

k fo

r (T

CP-f

rien

dly)

con

gest

ion

cont

rol

–Se

nder

app

cho

oses

an

appr

opri

ate

cong

esti

on c

ontr

ol m

echa

nism

–Co

re O

S im

plem

enta

tion

of

mec

hani

sms

–Lo

ts o

f ad

diti

onal

fea

ture

s: n

once

s, p

arti

al /

sep

arat

e ch

ecks

ums

(dis

ting

uish

: co

rrup

tion

⇔co

nges

tion

), .

..

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3838

Het

erog

eneo

us e

nvir

onm

ents

Het

erog

eneo

us e

nvir

onm

ents

TCP

over

hig

h sp

eed

links

:

•la

rger

init

ial w

indo

w /

win

dow

sca

ling

opti

on,

TCP

SACK

•Sc

alab

le T

CP:

incr

ease

/dec

reas

e fu

ncti

ons

chan

ged

(pro

bing

tim

es p

ropo

rtio

nal t

o rt

t bu

t no

t ra

te)

•H

ighS

peed

TCP

(mer

ged

wit

h Sc

alab

le T

CP):

resp

onse

fun

ctio

n le

ss d

rast

ic in

hig

h ba

ndw

idth

env

iron

men

ts o

nly

•Q

uick

-Sta

rt:

quer

y ro

uter

s fo

r in

itia

l sen

ding

rat

e w

ith

IP o

ptio

nsdr

aft

only

-se

ems

to b

e ab

ando

ned?

!

TCP

over

asy

mm

etri

c lin

ks:

•AC

K su

ppre

ssio

n, A

CK c

ompa

ctio

n, T

CP h

eade

r co

mpr

essi

on

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

3939

TCP

over

noi

sy (

wir

eles

s) li

nks

TCP

over

noi

sy (

wir

eles

s) li

nks

•Va

riou

s po

ssib

le e

nhan

cem

ents

:–

split

con

nect

ion

at b

ase

stat

ion

–m

onit

or c

onne

ctio

n at

bas

e st

atio

n, b

uffe

r +

inte

rfer

e (“

Snoo

p TC

P”)

•N

ote:

ECN

is n

ot a

ffec

ted

by li

nk n

oise

!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4040

Beyo

nd E

CNBe

yond

ECN

•AT

M:

Expl

icit

Rat

e Fe

edba

ck(p

art

of A

vaila

ble

Bit

Rate

(AB

R)se

rvic

e)RM

(re

sour

ce m

anag

emen

t) c

ells

:–

sent

by

send

er,

inte

rspe

rsed

wit

h da

ta c

ells

; bi

ts in

RM

cel

l set

by

swit

ches

•

NI b

it:

no in

crea

se in

rat

e (m

ild c

onge

stio

n),

(EF)

CI b

it:

like

Inte

rnet

ECN

•tw

o-by

te E

R (e

xplic

it r

ate)

fie

ld:

may

be

low

ered

by

cong

este

d sw

itch

•se

nder

’ se

nd r

ate

thus

min

imum

sup

port

able

rat

e on

pat

h!

•Pr

oble

m:

ATM

fai

led

(sca

labi

lity?

too

muc

h co

mpl

exit

y in

sw

itch

es?)

•Ex

peri

men

tal I

nter

net

appr

oach

es:

•M

ulti

leve

l ECN

(tw

o bi

ts),

eXp

ress

Con

trol

Pro

toco

l (XC

P),

CAD

PC/P

TP(m

y ow

n)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4141

Oth

er T

CP e

nhan

cem

ents

Oth

er T

CP e

nhan

cem

ents

•FA

ST T

CP–

Vari

ant

base

d on

win

dow

and

del

ay–

Del

ay a

llow

s fo

r ea

rlie

r ad

apta

tion

(aw

aren

ess

of g

row

ing

queu

e)–

Prov

en t

o be

sta

ble

–Co

mm

erci

ally

ann

ounc

ed +

pat

ent

prot

ecte

d, b

y St

even

Low

‘s C

alTe

ch g

roup

–an

othe

r de

lay-

base

d ex

ampl

e: T

CP V

egas

•TC

P W

estw

ood

–di

ffer

ent

resp

onse

fun

ctio

n (p

ropo

rtio

nal t

o ra

te)

–pr

oven

to

be s

tabl

e

•Lo

ts o

f ex

peri

men

tal A

ctiv

e Q

ueue

Man

agem

ent

sche

mes

out

the

re–

Adap

tive

RED

, BL

UE,

REM

, RI

O e

tc.

etc.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4242

How

to

desi

gn y

our

own

mec

hani

smH

ow t

o de

sign

you

r ow

n m

echa

nism

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4343

End

syst

ems:

Mea

sure

...

End

syst

ems:

Mea

sure

...

++w

ell s

tudi

ed

-- lea

ds t

o m

isin

terp

reta

tion

of t

rans

mis

sion

err

ors

thro

ughp

ut("

good

put"

)(

mea

n, f

luct

uati

ons,

pack

et lo

ss r

atio

..)

++ea

sy t

o m

easu

re

++in

depe

nden

t of

tra

nsm

issi

on e

rror

s

-- not

pra

ctic

al w

itho

ut t

hrou

ghpu

t

dela

y(

rtt,

one

way

del

ay,

jitt

er..

)

sim

ilar

dela

y, d

iffe

rent

av

aila

ble

band

wid

th!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4444

...

and

chan

ge!

...

and

chan

ge!

•lo

wer

laye

rs–

thro

ughp

ut(g

ap b

etw

een

pack

ets)

•w

indo

w b

ased

/ r

ate

base

d•

wel

l stu

died

, m

any

opti

ons

-ou

r m

ain

inte

rest

!–

pack

et s

ize

•la

rge:

rec

omm

ende

dle

ss o

verh

ead

•sm

all:

less

impa

ct o

f tr

ansm

issi

on e

rror

s,sm

alle

r la

tenc

y!–

prot

ocol

Not

e:

Not

e: p

acke

t si

ze =

gra

nula

rity

of

thro

ughp

ut m

easu

rem

ents

•co

nten

t–

com

pres

sion

–hi

erar

chic

al e

ncod

ing

–FE

C

Com

mon

dif

ficu

ltie

s:Co

mm

on d

iffi

cult

ies:

band

wid

th k

now

n (d

epen

ding

on

cont

ent)

?gr

anul

arit

y of

rat

e ch

ange

s

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4545

Mea

suri

ng t

he n

etw

ork

Mea

suri

ng t

he n

etw

ork

•W

hen

you

mea

sure

, yo

u m

easu

re t

he p

ast

–pr

edic

tion

s /

esti

mat

ions

wit

h a

?? %

cha

nce

of s

ucce

ss o

r co

ntro

l the

ory

•W

hen

you

mea

sure

, yo

u ch

ange

the

sys

tem

–th

ink

of u

nres

pons

ive

flow

s vs

. TC

P–

non-

intr

usiv

enes

s re

ally

impo

rtan

t (e

.g.,

mon

itor

TCP

beh

avio

r)

•M

easu

rem

ents

yie

ld n

o gu

aran

tees

–In

tern

et t

raff

ic =

res

ult

of u

ser

beha

vior

!

•Re

sear

ch c

arri

ed o

ut in

con

trol

labl

e, is

olat

ed e

nvir

onm

ents

–Fi

eld

tria

ls a

re a

nec

essa

ry e

xtra

whe

n yo

u kn

ow t

hat

som

ethi

ng w

orks

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4646

Poss

ibili

ties

in r

oute

rsPo

ssib

iliti

es in

rou

ters

•Co

mm

unic

ate

wit

h en

d sy

stem

s–

alte

r he

ader

fla

gs (

IP o

nly!

sho

uld

not

look

at

othe

r la

yers

)–

gene

rate

sig

nalin

g pa

cket

s: In

tern

et C

ontr

ol M

essa

ge P

roto

col (

ICM

P)(m

ainl

y er

ror

mes

sage

s)

•Co

ntro

l pac

kets

in q

ueue

s:us

e qu

eue

leng

th o

r po

siti

on in

que

ue t

o–

com

mun

icat

e („

mar

k“)

–dr

op,

mov

e to

oth

er q

ueue

etc

.

•Pr

oble

ms

–CP

U c

ycle

s sc

arce

in (

core

) In

tern

et r

oute

rs–

Scal

abili

ty!

(e.g

., n

o pe

r-fl

ow s

tate

)ex

ampl

e: IC

MP

Sour

ce Q

uenc

h fa

iled

(con

gest

ion

noti

fica

tion

in t

imes

of

cong

esti

on)

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4747

My

Ph.D

. re

cipe

:

My

Ph.D

. re

cipe

: --

))

Und

erly

ing

thou

ght:

“TCP

alw

ays

exce

eds

the

avai

labl

e ba

ndw

idth

in

orde

r to

det

ect

it

(whe

n it

is

alre

ady

too

late

). W

ould

n‘t

it b

e be

tter

to

ask

for

the

avai

labl

e ba

ndw

idth

?“

Proc

ess:

•de

sign

suc

h a

mea

ns:

“Per

form

ance

Tra

nspa

renc

y Pr

otoc

ol (

PTP)

“–

note

:m

ust

lead

to

abso

lute

ly g

reat

res

ults

in o

rder

to

just

ify

rout

er e

ffor

t!

•fi

nd o

ut h

ow t

o us

e th

e (a

vaila

ble

band

wid

th)

info

rmat

ion

...w

itho

ut b

eing

a c

ontr

ol t

heor

y gu

ru!

⇒th

e tr

icky

par

t!

•m

ixtu

re o

f in

tuit

ion,

mat

hs,

sim

ulat

ion,

..

Let‘s look

at this!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4848

Exte

nded

Use

of

Vect

or D

iagr

ams

Exte

nded

Use

of

Vect

or D

iagr

ams

•Pr

oble

m:

–St

abili

ty a

naly

sis

com

plex

–TC

P-lik

e m

echa

nism

des

ign

diff

icul

t

•So

luti

on:

–Ex

tend

ed u

se o

f ve

ctor

dia

gram

s!

•An

alyz

e ac

tual

res

ults

(fr

om s

imul

atio

n or

rea

l lif

e m

easu

rem

ents

)

•In

stea

d of

jus

t ex

plai

ning

a c

once

pt,

desi

gnin

the

2D

dia

gram

spa

ce!

–N

eces

sary

sim

plif

icat

ions

may

eve

n be

les

sdr

amat

ic!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

4949

How

Sta

ble

is A

IMD

/ a

sync

. RT

T?H

ow S

tabl

e is

AIM

D /

asy

nc.

RTT?

U 2

SER

Use

r 1

-0.0

500

0.00

00

0.05

00

0.10

00

0.15

00

0.20

00

0.25

00

0.30

00

0.35

00

0.40

00

0.45

00

0.50

00

0.55

00

0.60

00

0.65

00

0.70

00

0.75

00

0.80

00

0.85

00

0.90

00

0.95

00

1.00

00

0.00

000.

2000

0.40

000.

6000

0.80

001.

0000

Fluid model

(no queues, ..)

RTT: 7 vs. 2

AI=0.1, MD=0.5

Sim. time=175

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5050

Is A

IMD

dis

tort

ed in

TCP

?Is

AIM

D d

isto

rted

in T

CP?

TCP 2

TC

P 1

1.00

00

1.50

00

2.00

00

2.50

00

3.00

00

3.50

00

4.00

00

4.50

00

5.00

00

5.50

00

6.00

00

6.50

00

7.00

00

7.50

00

8.00

00

8.50

00

9.00

00

9.50

00

10.0

000

2.00

004.

0000

6.00

008.

0000

10.0

000

12.0

000

14.0

000

ns-2 simulator

TCP Tahoe

equal RTTs

1 bottleneck link

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5151

Vari

ous

othe

r Po

ssib

iliti

esVa

riou

s ot

her

Poss

ibili

ties

•An

alyz

e re

al li

fe d

ata

•An

alyz

e di

ffer

ent

mec

hani

sms

–m

ore

com

plex

fee

dbac

k: A

TM A

BR–

queu

eing

beh

avio

ur:

AQM

–..

.

•Pe

rfor

m a

naly

sis

in v

ecto

r di

agra

m s

pace

–pl

ot “

dist

ance

fro

m o

ptim

alit

y“ /

tim

e de

velo

pmen

t–

plot

tim

e of

con

verg

ence

/ u

ser

1 al

loca

tion

–..

.

•..

. ve

ctor

dia

gram

aid

ed d

esig

n!

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5252

Inte

ract

ive

Vect

or D

iagr

am A

ided

Des

ign

Inte

ract

ive

Vect

or D

iagr

am A

ided

Des

ign

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5353

A f

oolp

roof

Ph.

D.

thes

is r

ecip

eA

foo

lpro

of P

h.D

. th

esis

rec

ipe

•Ro

ughl

y fo

llow

thi

s ta

ble

from

1 t

o 7

...

if s

omet

hing

fai

ls,

goba

ck!

•In

my

case

:–

Leve

l 2:

intu

itio

n (f

oolin

g ar

ound

wit

h C

AVT)

–Le

vel 4

:th

e “H

eure

ka“

expe

rien

ce -

intu

itio

n w

as r

ight

!–

Leve

l 1:

shee

t of

pap

er–

Leve

l 3:

MS

Exce

l + C

AVT

refi

nem

ent

(foo

ling

arou

nd,

part

2)

–Le

vel 5

:th

e ty

pica

l ns

+ du

mbb

ell e

xper

ienc

e–

Leve

l 6:

addi

tion

al s

imul

atio

ns–

...

that

was

goo

d en

ough

. H

opin

g to

rea

ch le

vel 7

soo

n.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5454

Even

tual

ly:

CAD

PCEv

entu

ally

: CA

DPC

vs.

TCP

vs.

TCP

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5555

CAD

PC v

s. 3

TCP

(+EC

N)

CAD

PC v

s. 3

TCP

(+EC

N)

flav

ors

flav

ors

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5656

Refe

renc

esRe

fere

nces

1. C

onge

stio

n Co

ntro

l: a

qui

ck in

trod

ucti

on

•Ra

j Ja

in a

nd K

. K.

Ram

akri

shna

n, "

Cong

esti

on A

void

ance

in C

ompu

ter

Net

wor

ks w

ith

a Co

nnec

tion

less

Net

wor

k La

yer:

Con

cept

s, G

oals

and

Met

hodo

logy

'',Pr

ocee

ding

s of

Com

pute

r N

etw

orki

ng S

ympo

sium

, W

ashi

ngto

n, D

. C.

, Ap

ril 1

1-13

198

8, p

p. 1

34-1

43.

•Va

n Ja

cobs

on,

"Con

gest

ion

Avoi

danc

e an

d Co

ntro

l'',

Proc

eedi

ngs

of A

CM S

IGCO

MM

198

8, p

p. 3

14-

329.

•D

. Ch

iu a

nd R

. Ja

in,

"Ana

lysi

s of

the

Incr

ease

/Dec

reas

e Al

gori

thm

s fo

r Co

nges

tion

Avo

idan

ce in

Co

mpu

ter

Net

wor

ks'',

Jou

rnal

of

Com

pute

r N

etw

orks

and

ISD

N,

Vol.

17,

No.

1,

June

198

9, p

p. 1

-14.

•Sa

lly F

loyd

and

Van

Jac

obso

n, "

On

Traf

fic

Phas

e Ef

fect

s in

Pac

ket-

Swit

ched

Gat

eway

s'',

Inte

rnet

wor

king

: Re

sear

ch a

nd E

xper

ienc

e, V

.3 N

.3,

Sept

embe

r 19

92,

p.11

5-15

6. E

arlie

r ve

rsio

n:

Com

pute

r Co

mm

unic

atio

n Re

view

, V.

21 N

.2,

Apri

l 199

1.

•Sa

lly F

loyd

and

Van

Jac

obso

n, "

Rand

om E

arly

Det

ecti

on G

atew

ays

for

Cong

esti

on A

void

ance

'',

IEEE

/ACM

Tra

nsac

tion

s on

Net

wor

king

, Au

gust

199

3.

•K.

Ram

akri

shna

n, S

. Fl

oyd,

and

D.

Blac

k, "

The

Addi

tion

of

Expl

icit

Con

gest

ion

Not

ific

atio

n (E

CN)

to

IP'',

RFC

316

8, S

epte

mbe

r 20

01.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5757

Refe

renc

es /

2Re

fere

nces

/2

2. P

robl

ems

•Sc

ott

Shen

ker,

"Fu

ndam

enta

l D

esig

n Is

sues

for

the

Fut

ure

Inte

rnet

'', IE

EE J

ourn

al o

n Se

lect

ed A

reas

in

Com

mun

icat

ions

, 13

, pp

. 11

41-1

149,

199

5.

•Fr

ank

Kelly

, "C

harg

ing

and

rate

con

trol

for

ela

stic

tra

ffic

'', E

urop

ean

Tran

sact

ions

on

Tele

com

mun

icat

ions

, 8.

pp.

33-

37.

An u

pdat

ed v

ersi

on is

ava

ilabl

e at

ht

tp:/

/ww

w.s

tats

lab.

cam

.ac.

uk/f

rank

/ela

stic

.htm

l

•Ra

mes

h Jo

hari

, "M

athe

mat

ical

Mod

elin

g an

d Co

ntro

l of

Inte

rnet

Con

gest

ion"

, SI

AM N

ews,

Vol

. 33

, N

o. 2

.

•L.

Mas

soul

ié a

nd J

. Ro

bert

s, "

Band

wid

th s

hari

ng:

obje

ctiv

es a

nd a

lgor

ithm

s'',

Proc

eedi

ngs

of IE

EE

Info

com

199

9, N

ew Y

ork

City

, N

ew Y

ork,

21.

-25.

3.

1999

.

•Ra

mes

h Jo

hari

and

Dav

id T

an,

"End

-to-

End

Cong

esti

on C

ontr

ol f

or t

he In

tern

et:

Del

ays

and

Stab

ility

'', IE

EE/A

CM T

rans

acti

ons

on N

etw

orki

ng 9

(20

01)

818-

832.

•As

hraf

Mat

raw

y an

d Io

anni

s La

bada

ris,

"A

Surv

ey o

f Co

nges

iton

Con

trol

Sch

emes

for

Mul

tica

st V

ideo

Ap

plic

atio

ns",

IEEE

Com

mun

icat

ions

Sur

vey

& T

utor

ials

, Fo

urth

Qua

rter

200

3, V

ol.

5, N

o. 2

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5858

Refe

renc

es /

3Re

fere

nces

/3

3. S

ome

prop

osed

enh

ance

men

ts

•M

ark

E. C

rove

lla a

nd A

zer

Best

avro

s, ''

Self

-sim

ilari

ty in

Wor

ld W

ide

Web

Tra

ffic

: Ev

iden

ce a

nd

Poss

ible

Cau

ses''

, IE

EE/A

CM T

rans

acti

ons

on N

etw

orki

ng,

Vol.

5,

No.

6,

Dec

embe

r 19

97.

•An

dras

Ver

es,

Zsol

t Ke

nesi

, Sa

ndor

Mol

nar,

Gab

or V

atta

y, ''

On

the

Prop

agat

ion

of L

ong-

rang

e D

epen

denc

y in

the

Inte

rnet

'', P

roce

edin

gs o

f AC

M S

IGCO

MM

200

0, S

tock

holm

, Sw

eden

, Au

gust

28

-Se

ptem

ber

1 20

00.

•G

uang

hui H

e, Y

uan

Gao

, Je

nnif

er C

. H

ou,

Kiho

ng P

ark,

''A

Case

for

Exp

loit

ing

Self

-Sim

ilari

ty o

f N

etw

ork

Traf

fic

in T

CP'',

10t

h IE

EE In

tern

atio

nal C

onfe

renc

e on

Net

wor

k Pr

otoc

ols

(ICN

P'02

), P

aris

, Fr

ance

, N

ov.

12-1

5, 2

002.

•Jö

rg W

idm

er,

Robe

rt D

enda

, an

d M

arti

n M

auve

, "A

Sur

vey

on T

CP-F

rien

dly

Cong

esti

on C

ontr

ol'',

IE

EE N

etw

ork

Mag

azin

e, S

peci

al Is

sue

"Con

trol

of

Best

Eff

ort

Traf

fic'

' Vol

. 15

, N

o. 3

, M

ay 2

001.

•Ph

ilipp

e O

echs

lin a

nd J

on C

row

crof

t, "

Dif

fere

ntia

ted

End-

to-E

nd In

tern

et S

ervi

ces

usin

g a

Wei

ghte

d Pr

opor

tion

al F

air

Shar

ing

TCP"

, AC

M C

ompu

ter

Com

mun

icat

ion

Revi

ew (

CCR)

, 19

98.

•H

ari B

alak

rish

nan,

Har

ihar

an R

ahul

, an

d Sr

iniv

asan

Ses

han,

"An

Inte

grat

ed C

onge

stio

n M

anag

emen

t Ar

chit

ectu

re f

or In

tern

et H

osts

'', P

roce

edin

gs o

f AC

M S

IGCO

MM

199

9, C

ambr

idge

, M

A.,

Sept

embe

r 19

99.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

5959

Refe

renc

es /

4Re

fere

nces

/4

•H

. Ba

lakr

ishn

an a

nd S

. Se

shan

, "T

he C

onge

stio

n M

anag

er'',

RFC

312

4, J

une

2001

.

•Ed

die

Kohl

er,

Mar

k H

andl

ey,

Sally

Flo

yd,

and

Jite

ndra

Pad

hye,

"D

atag

ram

Con

gest

ion

Cont

rol P

roto

col

(DCC

P)",

Inte

rnet

-dra

ft (

wor

k in

pro

gres

s) d

raft

-iet

f-dc

cp-s

pec-

05.t

xt,

Oct

ober

2003

.

•M

etz,

C.,

"TC

P O

ver

Sate

llite

...

The

Fina

l Fro

ntie

r.",

IEEE

Inte

rnet

Com

puti

ng,

1999

.

•Sa

lly F

loyd

, "H

ighS

peed

TCP

for

Lar

ge C

onge

stio

n W

indo

ws"

,RF

C 36

49,

Expe

rim

enta

l, D

ecem

ber

2003

.

•Ba

lakr

ishn

an,

H.,

Pad

man

abha

n, V

. N

., S

esha

n, S

. an

d Ka

tz,

R. H

., "

A Co

mpa

riso

n of

Mec

hani

sms

for

Impr

ovin

g TC

P Pe

rfor

man

ce o

ver

Wir

eles

s Li

nks"

, Pr

ocee

ding

s of

ACM

SIG

COM

M 1

996,

Sta

nfor

d, C

A.

•Ra

mak

rish

nan,

K.,

Flo

yd,

S. a

nd B

lack

, D

., "

The

Addi

tion

of

Expl

icit

Con

gest

ion

Not

ific

atio

n (E

CN)

to

IP",

RFC

316

8.

•D

ina

Kata

bi,

Mar

k H

andl

ey,

and

Char

lie R

ohrs

, ''C

onge

stio

n Co

ntro

l for

Hig

h Ba

ndw

idth

-Del

ay P

rodu

ct

Net

wor

ks'',

Pro

ceed

ings

of

ACM

SIG

COM

M 2

002,

Pit

tsbu

rgh,

PA,

19-

23 A

ugus

t 20

02.

•Ch

eng

Jin,

Dav

id X

. W

ei a

nd S

teve

n H

. Lo

w,

''FAS

T TC

P: m

otiv

atio

n, a

rchi

tect

ure,

alg

orit

hms,

pe

rfor

man

ce'',

IEEE

Info

com

, M

arch

200

4.

Uni

Inn

sbru

ckU

ni I

nnsb

ruck

Info

rmat

ik

Info

rmat

ik --

6060

Refe

renc

es /

5Re

fere

nces

/5

4. H

ow t

o de

sign

you

r ow

n m

echa

nism

•M

icha

el W

elzl

, "V

ecto

r Re

pres

enta

tion

s fo

r th

e An

alys

is a

nd D

esig

n of

Dis

trib

uted

Co

ntro

ls",

Pro

ceed

ings

of

MIC

200

2 (I

ASTE

D M

odel

ling,

Iden

tifi

cati

on a

nd C

ontr

ol

Conf

eren

ce),

Inns

bruc

k, A

ustr

ia,

18-2

2 Fe

brua

ry 2

002.

•M

icha

el W

elzl

, M

ax M

ühlh

äuse

r: "

CAVT

-A

Cong

esti

on A

void

ance

Vis

ualiz

atio

n To

ol",

AC

M C

ompu

ter

Com

mun

icat

ion

Revi

ew,

Volu

me

33,

Issu

e 3,

Jul

y 20

03.

•M

icha

el W

elzl

: "S

cala

ble

Perf

orm

ance

Sig

nalli

ng a

nd C

onge

stio

n Av

oida

nce"

, Kl

uwer

Ac

adem

ic P

ublis

hers

, Au

gust

200

3. IS

BN 1

-402

0-75

70-7

. Fo

rew

ords

by

Jon

Crow

crof

t an

d M

ax M

ühlh

äuse

r.

CAVT

is a

vaila

ble

from

: ht

tp:/

/ww

w.w

elzl

.at/

tool

s/ca

vt/

Thank you!

IASTED PDCN 2004 Tutorial:Shaping the Future ofInternet Congestion ControlOutlineCongestion ControlProblem statementA simple router modelThe congestion problemCongestion collapseInternet congestion control: HistoryTCP Congestion Control /1: Tahoe, 1988TCP Congestion Control /2Background: AIMDActive Queue ManagementActive Queue Management /2Explicit Congestion Notification (ECN)ProblemsTCP in heterogeneous environmentsFairnessIssues with TCP-friendlinessProportional FairnessCongestion pricingEnd2end real-time data transferMultimedia adaptationCongestion Control and Quality of ServiceSpecial types of trafficSome reasons for TCP stability“Proofs“ of TCP stabilityUnicast / Broadcast / (overlay) MulticastMu