Addressing the Challenges of Web Data Transport fileAddressing the Challenges of Web Data Transport...
29
Addressing the Challenges of Web Data Transport Venkata N. Padmanabhan Microsoft Research UW Whistler Retreat December 1998
Transcript of Addressing the Challenges of Web Data Transport fileAddressing the Challenges of Web Data Transport...
Add
ress
ing
the
Cha
lleng
es o
fW
eb D
ata
Tra
nspo
rt
Ven
kata
N. P
adm
anab
han
Mic
roso
ft R
esea
rch
UW
Whi
stle
r R
etre
atD
ecem
ber
1998
Out
line
•C
halle
nges
•So
lutio
ns–
TC
P Se
ssio
n
–Fa
st S
tart
•O
ngoi
ng a
nd F
utur
e W
ork
The
Big
Pic
ture
Inte
rnet
Ser
ver
Sate
llite
Cab
le
Mod
emC
lien
t
Cli
ent
Ser
ver
Goa
l: T
rans
fer
data
fro
m s
erve
rs to
clie
nts
effi
cien
tly
Why
is th
is h
ard?
#1: M
ultip
le in
depe
nden
t com
pone
nts
#2: B
urst
y da
ta tr
ansf
ers
#3: A
cces
s ne
twor
k ch
arac
teri
stic
s
#1: M
ultip
le I
ndep
ende
nt C
ompo
nent
s
Inte
rlea
ved
data
str
eam
⇒ u
ndes
irab
le c
oupl
ing
Imag
e #1
Imag
e #2
stal
l
Imag
e #1
Imag
e #2
Con
curr
ent d
ata
stre
ams
⇒ c
ompe
titio
n
#2: B
urst
y D
ata
Tra
nsfe
rs
Latency
Ban
dwid
th
Tel
net
Bul
k
Web
•D
ownl
oad
time
sens
itive
to la
tenc
y &
ban
dwid
th
•Sh
ared
net
wor
k ⇒
nee
d to
pro
be b
efor
e us
e
Pro
bing
for
ban
dwid
th r
equi
res
time
#1: H
ow to
avo
id c
ompe
titio
n an
dco
uplin
g?•
HT
TP/
1.0
–av
oids
cou
plin
g bu
t not
com
petit
ion
•P-
HT
TP
[PM
94]
–av
oids
com
petit
ion
but n
ot c
oupl
ing
•T
CP
Con
trol
Blo
ck I
nter
depe
nden
ce [
T97
]–
avoi
ds c
oupl
ing
–av
oids
com
petit
ion
at th
e tim
e of
initi
aliz
atio
n bu
tno
t bey
ond
TC
P Se
ssio
n
Dec
oupl
e se
rvic
e m
odel
fro
m tr
ansp
ort a
lgor
ithm
s
Send
erR
ecei
ver
App
licat
ion
App
licat
ion
TC
P Se
ssio
n
TC
PT
CP
TC
PT
CP
TC
PT
CP
Send
er-s
ide
chan
ges
⇒ e
asy
to d
eplo
y in
crem
enta
lly
TC
P Se
ssio
n
TC
P se
ssio
n co
mpo
nent
s
•In
tegr
ated
con
gest
ion
cont
rol
•C
onne
ctio
n sc
hedu
ling
•In
tegr
ated
loss
rec
over
y
Flex
ible
gra
nula
rity
of
inte
grat
ion
(def
ault:
hos
t-pa
ir)
Con
gest
ion
Con
trol
and
Sch
edul
ing
Key
idea
: how
muc
h da
ta, n
ot w
hat d
ata
•U
nifi
ed c
onge
stio
n w
indo
w c
ontr
ols
amou
nt o
fse
ssio
n-w
ide
outs
tand
ing
data
•W
indo
w g
row
th a
nd s
hrin
kage
not
tied
to th
enu
mbe
r of
con
nect
ions
•D
ecou
ple
conn
ectio
n sc
hedu
ling
from
cong
estio
n co
ntro
l
Com
petin
g T
CP
Con
nect
ions
Tim
e (s
econ
ds)
Data transferred (KB)
4 co
ncur
rent
co
nnec
tions
1.5
Mbp
s/50
ms
emul
ated
link
Com
petit
ion
lead
s to
inco
nsis
tent
per
form
ance
0
20406080100
120
140
02
46
Shar
ing
with
TC
P Se
ssio
n
Tim
e (s
econ
ds)
Data transferred (KB)
BSD
/OS
impl
emen
tatio
n
4 co
ncur
rent
conn
ectio
ns
1.5
Mbp
s/50
ms
emul
ated
link
Shar
ing
lead
s to
mor
e co
nsis
tent
per
form
ance
020406080100
120
140
02
46
Inte
grat
ed L
oss
Rec
over
y
21
32
1Se
rver
Clie
nt1
21
2
4
2
Key
idea
: use
pac
ket o
rder
ing
info
rmat
ion
acro
ssco
nnec
tions
to im
prov
e da
ta-d
rive
n lo
ss r
ecov
ery
dupl
icat
e ac
kla
ter
ack
Perf
orm
ance
# cl
ient
s
Download time per client (sec)
Serv
er a
nd c
lient
s co
nnec
ted
via
1.5
Mbp
s/50
ms
link
4 co
ncur
rent
10
KB
tran
sfer
s be
twee
nse
rver
and
eac
h cl
ient
2-3X
red
uctio
n in
dow
nloa
d tim
e
0246810121416
04
812
1620
inde
pend
ent T
CP
conn
ectio
ns
TC
P se
ssio
n
Pack
et L
oss
# cl
ient
s
# packet losses / timeouts
2X r
educ
tion
in p
acke
t los
ses
due
to in
tegr
ated
con
gest
ion
ctrl
.10
X r
educ
tion
in ti
meo
uts
due
to in
tegr
ated
loss
rec
over
y.
04080120
160
200
04
812
1620
inde
pend
ent T
CP
conn
ectio
ns
TC
P se
ssio
n
2X b
ette
r
L L10
X b
ette
r
TT
L: l
oss
T: t
imeo
ut
Sum
mar
y of
TC
P Se
ssio
n
Key
idea
: sep
arat
ion
of T
CP
func
tion
alit
y
Adv
anta
ges
over
inde
pend
ent T
CP
conn
ectio
ns
•Fe
wer
pac
ket l
osse
s
•B
ette
r lo
ss r
ecov
ery
•M
ore
cont
rol o
ver
sche
dulin
g of
dat
a st
ream
s
Adv
anta
ges
over
P-H
TT
P
•N
o co
uplin
g be
twee
n co
ncur
rent
dat
a st
ream
s
•N
ot ti
ed to
spe
cifi
c ap
plic
atio
n
•C
hang
es c
onfi
ned
to s
ende
r si
de
Ban
dwid
th P
robi
ng in
TC
P
•Sl
ow-s
tart
pro
bing
–ex
pone
ntia
l gro
wth
in c
onge
stio
n w
indo
w s
tart
ing
with
a s
ize
of o
ne s
egm
ent
–ac
k cl
ocki
ng a
void
s bu
rstin
ess
•L
inea
r pr
obin
g
•W
hen
is s
low
-sta
rt p
robi
ng in
itiat
ed?
–up
on c
onne
ctio
n st
art u
p
–up
on r
esta
rt a
fter
an
idle
per
iod
•H
ow d
oes
it im
pact
late
ncy?
–n-
segm
ent t
rans
fer
⇒ a
t lea
st lo
g n
RT
Ts
#2: H
ow to
red
uce
cost
of
prob
ing?
•P-
HT
TP
[PM
94]
–av
oid
repe
ated
pro
bing
for
com
pone
nts
of a
sin
gle
Web
pag
e bu
t not
acr
oss
page
s
•4K
slo
w-s
tart
[A
FP98
]
•R
ate-
base
d Pa
cing
[V
H97
]–
smoo
th o
ut u
sing
est
imat
e of
con
nect
ion
rate
–bu
t the
est
imat
e co
uld
itsel
f be
sta
le
TC
P Fa
st S
tart
Bas
ic id
ea:
use
cach
ed n
etw
ork
para
met
ers
tore
duce
the
cost
of
prob
ing
•R
euse
mos
t rec
ent s
ucce
ssfu
l win
dow
siz
e–
slow
-sta
rt ⇒
old
cwnd
/2, l
inea
r ph
ase
⇒ o
ldcw
nd-1
•E
stim
ate
conn
ectio
n’s
rate
as
cwnd
/srt
t
•B
reak
up
larg
e bu
rst i
nto
max
burs
t-si
zed
burs
ts
32
1Se
rver
Clie
nt5
23
1
54
6
46
Dyn
amic
s of
Fas
t Sta
rt
05101520253035
01
23
0
1020304050
01
23
FS TC
P
FS TC
P
Con
gest
ion
win
dow
(K
B)
Sequ
ence
num
ber
(KB
)
Dat
a tr
ansf
er o
ver
Dir
ecPC
sat
ellit
e ne
twor
k
0.95
2.60
Tim
e (s
ec)
Tim
e (s
ec)
Rob
ustn
ess
of F
ast S
tart
Goa
l: F
ast s
tart
sho
uld
help
whe
n ca
ched
info
isva
lid b
ut n
ot h
urt w
hen
it is
sta
le
Stud
ies
indi
cate
that
ava
ilabl
e ba
ndw
idth
is o
ften
stab
le f
or s
ever
al m
inut
es [
P97,
BSS
K97
]
But
we
need
to g
uard
aga
inst
sta
lene
ss
•Pr
otec
ting
othe
rs
•Pr
otec
ting
ones
elf
Prot
ectin
g O
ther
s
•E
nabl
es c
ontr
ol o
n tim
e sc
ale
fine
r th
an R
TT
•A
void
s po
tent
ial c
onge
stio
n co
llaps
e
R
F
S
F
in-p
rofi
le
out-
of-p
rofi
le
Pro
tect
oth
ers
from
ove
r-ag
gres
sive
fast
sta
rt
Pref
eren
tially
dro
p fa
st s
tart
pac
kets
(ex
cept
fir
st o
ne)
Prot
ectin
g O
nese
lf
Pro
tect
one
self
from
con
sequ
ence
s of
bur
st lo
ss
Qui
ckly
det
ect a
nd a
bort
fai
led
fast
sta
rt a
ttem
pt
•Fi
ne-g
rain
ed r
eset
tim
er d
urin
g fa
st s
tart
pha
se–
tied
to th
e fa
st T
CP
tim
er (
200
ms)
•If
res
et ti
mer
exp
ires
, abo
rt f
ast s
tart
–re
set c
wnd
to o
ne s
egm
ent,
initi
ate
slow
sta
rt
–no
oth
er c
onge
stio
n co
ntro
l pen
altie
s•
ssth
resh
not
hal
ved,
RT
O n
ot b
acke
d of
f
•A
bort
als
o w
hen
mul
tiple
loss
es w
ithin
RT
T
Impa
ct o
f St
alen
ess
on O
nese
lf
Abo
rtin
g fa
st s
tart
in c
ase
of f
ailu
re p
reve
nts
sign
ific
ant p
erfo
rman
ce d
egra
datio
n1.5
Mbp
s50
ms
051015202530
02
46
810
# o
f co
mp
etin
g b
ulk
tra
nsf
ers
Download Time (seconds)
TC
PFS FS
-CO
AR
SEFS
-NO
-AB
OR
T
Impa
ct o
f St
alen
ess
on O
ther
s
Prio
rity
dro
ppin
g si
gnif
ican
tly d
ecre
ases
adv
erse
impa
ct o
n co
mpe
ting
traf
fic
2150
2200
2250
2300
2350
2400
2450
2500
2550
1920
2122
2324
25
Tim
e (s
ec)
Segment #
FS FS w
/o P
-Dro
p
Asy
mm
etri
c A
cces
s N
etw
ork
•Pr
oble
m: u
pstr
eam
dat
a pa
cket
s bl
ock
acks
–R
TT
can
bec
ome
very
larg
e
•Po
ssib
le s
olut
ion:
ack
s-fi
rst s
ched
ulin
g [B
PK97
]–
but R
TT
can
stil
l be
larg
e du
e to
the
pack
et in
tran
smis
sionW
WW
W
Serv
erC
lient
WW
EE
EE
E
Impa
ct o
f B
idir
ectio
nal T
raff
ic
Fast
sta
rt h
elps
eve
n th
ough
the
inhe
rent
RT
T is
not l
arge
051015202530
FIF
OA
cks-
firs
t
TC
PF
S
Download Time (seconds)
175
KB
pag
edo
wnl
oad
over
10 M
bps/
28.8
Kbp
sne
twor
k
Sum
mar
y an
d C
oncl
usio
ns
•T
CP
Sess
ion
–de
coup
les
serv
ice
mod
el f
rom
tran
spor
t alg
orith
ms
–en
able
s co
ncur
renc
y w
ithou
t com
petit
ion
•Fa
st S
tart
–ex
ploi
ts d
iffe
rent
iate
d se
rvic
es to
com
plem
ent e
nd-
to-e
nd c
ontr
ol w
ith f
aste
r tim
e-sc
ale
cont
rol
–im
prov
es b
andw
idth
util
izat
ion
in th
e co
mm
on c
ase
–av
oids
ris
k of
per
form
ance
deg
rada
tion
in th
e w
orst
case
Con
clus
ions
•Fa
st s
tart
is r
obus
t–
sign
ific
ant b
enef
it (2
X)
in f
avor
able
con
ditio
ns
–lit
tle p
erfo
rman
ce d
egra
datio
n in
adv
erse
con
ditio
ns•
prio
rity
dro
ppin
g, q
uick
det
ectio
n of
fai
led
fast
sta
rt
•R
educ
ed la
tenc
y he
lps
both
clie
nts
and
serv
ers
–cl
ient
: fas
ter
dow
nloa
ds
–se
rver
: res
ourc
es f
reed
up
mor
e qu
ickl
y
•Si
gnif
ican
t ben
efit
with
new
acc
ess
netw
orks
–sa
telli
te, c
able
mod
em
–pr
ovid
es p
ath
for
incr
emen
tal d
eplo
ymen
t
