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525
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
525
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Seri
al P
erip
hera
l Int
erfa
ce (S
PI)
Full
Du
ple
x, 4
-wir
e, fl
exib
le c
lock
rat
e
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
521
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
521
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
5: S
essi
on
Laye
r
• Se
rvic
e: C
oo
rdin
atio
n o
f th
e d
ialo
gue
bet
wee
n a
pp
licat
ion
pro
gram
s
• Fu
nct
ion
s: S
essi
on
est
ablis
hm
ent,
man
agem
ent,
term
inat
ion
• Ex
amp
les:
RPC
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
517
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
517
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
1: P
hysi
cal L
ayer
• Se
rvic
e: T
ran
smis
sio
n o
f a r
aw b
it s
trea
m
ove
r a
com
mu
nic
atio
n c
han
nel
• Fu
nct
ion
s: C
on
vers
ion
of b
its
into
ele
ctri
cal o
r o
pti
cal s
ign
als
• Ex
amp
les:
X.2
1, E
ther
net
(cab
le, d
etec
tors
& a
mp
lifi e
rs)
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
513
8D
istr
ibut
ed S
yste
ms
Uw
e R
. Zim
mer
- T
he A
ustr
alia
n N
atio
nal U
nive
rsity
Syst
ems,
Net
wo
rks
& C
on
curr
ency
201
9
526
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
526
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Seri
al P
erip
hera
l Int
erfa
ce (S
PI)
MISO
MOSI
SCK
CS
time
SetSa
mp
le Set
Set
Set
Set
Set
Set
Set
Sam
ple
Sam
ple
Sam
ple
Sam
ple
Sam
ple
Sam
ple
Sam
ple
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
Clo
ck p
has
e an
d
po
lari
ty n
eed
to
be
agre
ed u
po
n
522
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
522
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
6: P
rese
ntat
ion
Laye
r
• Se
rvic
e: P
rovi
sio
n o
f pla
tfo
rm in
dep
end
ent c
od
ing
and
en
cryp
tio
n
• Fu
nct
ion
s: C
od
e co
nve
rsio
n, e
ncr
ypti
on
, vir
tual
dev
ices
• Ex
amp
les:
ISO
co
de
con
vers
ion
, PG
P en
cryp
tio
n
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
518
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
518
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
2: D
ata
Link
Lay
er
• Se
rvic
e: R
elia
ble
tran
sfer
of f
ram
es o
ver
a lin
k
• Fu
nct
ion
s: S
ynch
ron
izat
ion
, err
or
corr
ecti
on
, flo
w c
on
tro
l
• Ex
amp
les:
HD
LC (h
igh
leve
l dat
a lin
k co
ntr
ol p
roto
col)
, LA
P-B
(lin
k ac
cess
pro
ced
ure
, bal
ance
d),
LAP-
D (l
ink
acce
ss p
roce
du
re, D
-ch
ann
el),
LLC
(lin
k le
vel c
on
tro
l), …
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
514
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
514
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Ref
eren
ces
for
this
cha
pter
[ Bac
on1
998 ]
Bac
on
, J
Co
ncu
rren
t Sys
tem
s A
dd
iso
n W
esle
y Lo
ngm
an
Ltd
(2n
d e
dit
ion
) 199
8
[ Ben
2006
] B
en-A
ri, M
Pr
inci
ple
s o
f Co
ncu
rren
t an
d D
is-
trib
ute
d P
rogr
amm
ing
seco
nd
ed
itio
n, P
ren
tice
-Hal
l 200
6
[ Sch
neid
er19
90 ]
Sch
nei
der
, Fre
d
Imp
lem
enti
ng
fau
lt-t
ole
ran
t ser
vice
s u
sin
g th
e st
ate
mac
hin
e ap
pro
ach
: a tu
tori
al
AC
M C
om
pu
tin
g Su
rvey
s 19
90
vol.
22 ( 4
) pp
. 299
-319
[ Tan
enb
aum
2001
] Ta
nen
bau
m, A
nd
rew
D
istr
ibu
ted
Sys
tem
s: P
rin
-ci
ple
s an
d P
arad
igm
s Pr
enti
ce H
all 2
001
[ Tan
enb
aum
2003
] Ta
nen
bau
m, A
nd
rew
C
om
pu
ter N
etw
ork
s Pr
enti
ce H
all,
2003
527
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
527
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
(SP
I)
Seri
al P
erip
hera
l Int
erfa
ce (S
PI)
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
fro
m S
TM32
L4x6
ad
van
ced
AR
M®-
bas
ed 3
2-b
it M
CU
s re
fere
nce
man
ual
: Fig
ure
420
on
pag
e 12
91
1 sh
ift r
egis
ter?
FIFO
s?
Dat
a co
nn
ecte
d to
an
inte
rnal
bu
s?
CR
C?
DM
A?
Spee
d?
523
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
523
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
7: A
pp
licat
ion
Laye
r
• Se
rvic
e: N
etw
ork
acc
ess
for
app
licat
ion
pro
gram
s
• Fu
nct
ion
s: A
pp
licat
ion
/OS
spec
ific
• Ex
amp
les:
API
s fo
r m
ail,
ftp
, ssh
, scp
, dis
cove
ry p
roto
cols
…
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
519
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
519
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
3: N
etw
ork
Lay
er
• Se
rvic
e: T
ran
sfer
of p
acke
ts in
sid
e th
e n
etw
ork
• Fu
nct
ion
s: R
ou
tin
g, a
dd
ress
ing,
sw
itch
ing,
co
nge
stio
n c
on
tro
l
• Ex
amp
les:
IP, X
.25
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
515
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
515
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
OSI
net
wo
rk r
efer
ence
mo
del
Stan
dar
diz
ed a
s th
eO
pen
Syst
ems
Inte
rcon
nect
ion
(OSI
) ref
eren
ce m
od
el b
y th
e In
tern
atio
nal
Sta
nd
ard
izat
ion
Org
aniz
atio
n (I
SO) i
n 1
977
• 7
laye
r ar
chit
ectu
re
• C
on
nec
tio
n o
rien
ted
Har
dy
imp
lem
ente
d a
nyw
her
e in
full
…
…b
ut i
ts c
once
pts
and
term
inol
ogy
are
wid
ely
use
d,
wh
en d
escr
ibin
g ex
isti
ng
and
des
ign
ing
new
pro
toco
ls …
528
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
528
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
(SP
I)R
ecei
ve s
hift
regi
ster
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
S1C
SSl
ave
sele
ctor
Mas
ter
Slav
e 1
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 2
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 3
MIS
O
MO
SI
SCK CS
MIS
O
MO
SI
SCK CS
S2 S3
Full
du
ple
x w
ith
1
ou
t of x
sla
ves
524
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
524
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Seri
al P
erip
hera
l Int
erfa
ce (S
PI)
Use
d b
y ga
zilli
on
s o
f dev
ices
… a
nd
it
’s n
ot e
ven
a fo
rmal
sta
nd
ard
!
Sp
eed
on
ly li
mit
ed b
y w
hat
b
oth
sid
es c
an s
urv
ive.
Usu
ally
pu
sh-p
ull
dri
vers
, i.e
. fas
t an
d r
elia
ble
, yet
no
t fri
end
ly to
wro
ng
wir
ing/
pro
gram
min
g.
1.8”
CO
LOR
TFT
LC
D d
isp
lay
fro
m A
daf
ruit
San
Dis
k m
arke
tin
g p
ho
to
520
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
520
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
4: T
rans
po
rt L
ayer
• Se
rvic
e: T
ran
sfer
of d
ata
bet
wee
n h
ost
s
• Fu
nct
ion
s: C
on
nec
tio
n e
stab
lish
men
t, m
anag
emen
t, te
rmin
atio
n, fl
ow
-co
ntr
ol,
mu
ltip
lexi
ng,
err
or
det
ecti
on
• Ex
amp
les:
TC
P, U
DP,
ISO
TP0
-TP4
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
516
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
516
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
Net
wo
rk
Dat
a lin
k
Phys
ical
Use
r d
ata
Use
r d
ata
OSI
Net
wo
rk L
ayer
s
541
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
541
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Fib
re C
hann
elM
app
ing
of F
ibre
Ch
ann
el to
OSI
laye
rs:
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
IP
Phys
ical
Use
r d
ata
Use
r d
ata
OSI
TCP/
IPO
SI
IP
Phys
ical
Ap
plic
atio
n
FC/I
P
FC-0
Ap
plic
atio
n
Fib
reC
hann
el
FC-4
FC-4
FC
-3FC
-2FC
-3
FC-2
FC-1
Tran
spo
rtTr
ansp
ort
Net
wo
rkN
etw
ork
Ap
plic
atio
n
FC-3
Co
mm
on
se
rvic
e
FC-4
Pro
toco
l map
pin
g
FC-2
Ne
two
rk
FC-0
Ph
ysic
al
FC-1
Dat
a li
nk
537
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
537
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ethe
rnet
/ IE
EE 8
02.1
1
Wir
eles
s lo
cal a
rea
net
wo
rk (W
LAN
) dev
elo
ped
in th
e 90
’s
• Fi
rst s
tan
dar
d a
s IE
EE 8
02.1
1 in
199
7 (1
-2 M
bp
s o
ver
2.4
GH
z).
• Ty
pic
al u
sage
at 5
4 M
bp
s o
ver
2.4
GH
z ca
rrie
r at
20
MH
z b
and
wid
th.
• C
urr
ent s
tan
dar
ds
up
to 7
80 M
bp
s (8
02.1
1ac)
ove
r 5
GH
z ca
rrie
r at
160
MH
z b
and
wid
th.
• Fu
ture
sta
nd
ard
s ar
e d
esig
ned
for
up
to 1
00 G
bp
s o
ver
60 G
Hz
carr
ier.
• D
irec
t rel
atio
n to
IEEE
802
.3 a
nd
sim
ilar
OSI
laye
r as
soci
atio
n.
Car
rier
Sen
se M
ulti
ple
Acc
ess
wit
h C
ollis
ion
Avo
idan
ce (C
SMA
/CA
)
Dir
ect-
Sequ
ence
Spr
ead
Spec
trum
(D
SSS)
533
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
533
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
IP
Net
wo
rk
Phys
ical
OSI
Ap
ple
Talk
ove
r IP
Eth
erTa
lk L
ink
Acc
ess
Pro
toco
lLo
calT
alk
Lin
k A
cces
s Pr
oto
col
Toke
nTa
lk L
ink
Acc
ess
Pro
toco
lFD
DIT
alk
Lin
k A
cces
s Pr
oto
col
IEEE
802
.3Lo
calT
alk
Toke
n R
ing
IEEE
802
.5FD
DI
Ap
ple
Talk
Fili
ng
Pro
toco
l (A
FP)
Ro
uti
ng
Tab
le
Mai
nte
nan
ce P
rot.
AT
Up
dat
e B
ased
Ro
uti
ng
Pro
toco
lA
T Tr
ansa
ctio
n
Pro
toco
lN
ame
Bin
din
g Pr
oto
col
AT
Ech
o
Pro
toco
l
AT
Dat
a St
ream
Pro
toco
lA
T Se
ssio
n P
roto
col
Zo
ne
Info
Pro
toco
lPr
inte
r A
cces
s Pr
oto
col
Dat
agra
m D
eliv
ery
Pro
toco
l (D
DP)
App
leTa
lk A
ddre
ss R
eso
luti
on
Pro
toco
l (A
AR
P)
529
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
529
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
(SP
I)R
ecei
ve s
hift
regi
ster
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
OSI
MO
SI
SCK
SCK
S1C
SSl
ave
sele
ctor
Mas
ter
Slav
e 1
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 2
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 3
MO
SI
SCK CS
MO
SI
SCK CS
S2 S3
Co
ncu
rren
t sim
ple
x w
ith
y o
ut o
f x s
lave
s
542
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
542
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Infi n
iBan
d
• D
evel
op
ed in
the
late
90’
s
• D
efi n
ed b
y th
e In
fi n
iBan
d T
rad
e A
sso
ciat
ion
(IB
TA) s
ince
199
9.
• C
urr
ent s
tan
dar
ds
allo
w fo
r 25
Gb
ps
per
lin
k.
• Sw
itch
ed fa
bri
c to
po
logi
es.
• C
on
curr
ent d
ata
links
po
ssib
le (c
om
mo
nly
up
to 1
2 3
00 G
bp
s).
• D
efi n
es o
nly
the
dat
a-lin
k la
yer a
nd
par
ts o
f th
e n
etw
ork
laye
r.
• Ex
isti
ng
dev
ices
use
co
pp
er c
able
s (i
nst
ead
of o
pti
cal fi
bre
s).
Mo
stly
use
d in
su
per
-co
mp
ute
rs a
nd
clu
ster
s b
ut a
pp
licab
le to
sto
rage
arr
ays
as w
ell.
Ch
eap
er th
an E
ther
net
or
Fib
reC
han
nel
at h
igh
dat
a-ra
tes.
Sm
all p
acke
ts (o
nly
up
to 4
kB
) an
d n
o s
essi
on
co
ntr
ol.
538
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
538
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Blu
eto
oth
Wir
eles
s lo
cal a
rea
net
wo
rk (W
LAN
) dev
elo
ped
in th
e 90
’s w
ith
dif
fere
nt f
eatu
res
than
802
.11:
• Lo
wer
po
wer
co
nsu
mp
tio
n.
• Sh
ort
er r
ange
s.
• Lo
wer
dat
a ra
tes
(typ
ical
ly <
1 M
bp
s).
• A
d-h
oc
net
wo
rkin
g (n
o in
fras
tru
ctu
re r
equ
ired
).
Co
mb
inat
ion
s o
f 802
.11
and
Blu
eto
oth
OSI
laye
rsar
e p
oss
ible
to a
chie
ve th
e re
qu
ired
feat
ure
s se
t.
534
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
534
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ethe
rnet
/ IE
EE 8
02.3
Loca
l are
a n
etw
ork
(LA
N) d
evel
op
ed b
y X
ero
x in
the
70’s
• 10
Mb
ps
spec
ifica
tio
n 1
.0 b
y D
EC, I
nte
l, &
Xer
ox
in 1
980.
• Fi
rst s
tan
dar
d a
s IE
EE 8
02.3
in 1
983
(10
Mb
ps
ove
r th
ick
co-a
x ca
ble
s).
• cu
rren
tly
1 G
bp
s (8
02.3
ab) c
op
per
cab
le p
ort
s u
sed
in m
ost
des
kto
ps
and
lap
top
s.
• cu
rren
tly
stan
dar
ds
up
to 1
00 G
bp
s (I
EEE
802.
3ba
2010
).
• m
ore
than
85
% o
f cu
rren
t LA
N li
nes
wo
rld
wid
e (a
cco
rdin
g to
the
Inte
rnat
ion
al D
ata
Co
rpo
rati
on
(ID
C))
.
Car
rier
Sen
se M
ulti
ple
Acc
ess
wit
h C
ollis
ion
Det
ecti
on (C
SMA
/CD
)
530
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
530
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
(SP
I)R
ecei
ve s
hift
regi
ster
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Master
Slave
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Clo
ck g
ener
ator
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
rM
ISO
MIS
O
MO
SIM
OSI
SCK
SCK
NSS
CS
Slav
e se
lect
or
Mas
ter
Slav
e 1
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 2
Rec
eive
shi
ft re
gist
er
Tran
smit
shift
reg
iste
r
Slav
e 3
MIS
O
MO
SI
SCK CS
MIS
O
MO
SI
SCK CS
Co
ncu
rren
t d
aisy
ch
ain
ing
wit
h a
ll sl
aves
543
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
543
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
utio
n!
Mo
tiva
tio
nPo
ssib
ly …
… fi
ts a
n e
xist
ing
phys
ical
dis
trib
utio
n (e
-mai
l sys
tem
, dev
ices
in a
larg
e cr
aft,
…).
… h
igh
perf
orm
ance
du
e to
po
ten
tial
ly h
igh
deg
ree
of p
aral
lel p
roce
ssin
g.
… h
igh
relia
bilit
y/in
tegr
ity
du
e to
red
un
dan
cy o
f har
dw
are
and
so
ftw
are.
… s
cala
ble.
… in
tegr
atio
n o
f h
eter
oge
neo
us
dev
ices
.
Dif
fere
nt s
pec
ifi ca
tio
ns
will
lead
to s
ub
stan
tial
ly d
iffe
ren
t dis
trib
ute
d d
esig
ns.
539
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
539
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Toke
n R
ing
/ IE
EE 8
02.5
/
Fib
re D
istr
ibut
ed D
ata
Inte
rfac
e (F
DD
I)
• “T
oke
n R
ing
“ d
evel
op
ed b
y IB
M in
the
70’s
• IE
EE 8
02.5
sta
nd
ard
is m
od
elle
d a
fter
the
IBM
To
ken
Rin
g ar
chit
ectu
re(s
pec
ifi ca
tio
ns
are
slig
htl
y d
iffe
ren
t, b
ut b
asic
ally
co
mp
atib
le)
• IB
M T
oke
n R
ing
req
ues
ts a
re s
tar
top
olo
gy a
s w
ell a
s tw
iste
d p
air
cab
les,
wh
ile IE
EE 8
02.5
is u
nsp
ecifi
ed in
top
olo
gy a
nd
med
ium
• Fi
bre
Dis
trib
ute
d D
ata
Inte
rfac
e co
mb
ines
a to
ken
rin
g ar
chit
ectu
re
wit
h a
du
al-r
ing,
fi b
re-o
pti
cal,
ph
ysic
al n
etw
ork
.
Un
like
CSM
A/C
D, T
oken
rin
g is
det
erm
inis
tic
(wit
h r
esp
ect t
o it
s ti
min
g b
ehav
iou
r)
FD
DI i
s de
term
inis
tic
and
failu
re r
esis
tant
No
ne
of t
he
abo
ve is
cu
rren
tly
use
d in
per
form
ance
ori
ente
d a
pp
licat
ion
s.
535
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
535
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ethe
rnet
/ IE
EE 8
02.3
O
SI r
elat
ion
: PH
Y, M
AC
, MA
C-c
lien
t
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
OS
Ire
fere
nce
mod
el
App
licat
ion
Pre
sent
atio
n
Ses
sion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phy
sica
l
IEE
E 8
02.3
refe
renc
em
odel
MA
C-c
lient
Med
ia A
cces
s (M
AC
)
Phy
sica
l (P
HY
)
Upp
er-la
yer
prot
ocol
s
IEE
E 8
02-s
peci
fic
IEE
E 8
02.3
-spe
cific
Med
ia-s
peci
fic
531
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
531
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
IP
Net
wo
rk
Phys
ical
Use
r d
ata
Use
r d
ata
OSI
Tran
spo
rt
Ap
plic
atio
n
TCP/
IPO
SI
544
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
544
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Wha
t ca
n b
e d
istr
ibut
ed?
• St
ate
C
om
mo
n o
per
atio
ns
on
dis
trib
ute
d d
ata
• Fu
ncti
on
Dis
trib
ute
d o
per
atio
ns
on
cen
tral
dat
a
• St
ate
& F
unct
ion
C
lien
t/se
rver
clu
ster
s
• no
ne o
f tho
se
Pu
re r
eplic
atio
n, r
edu
nd
ancy
540
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
540
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Fib
re C
hann
el
• D
evel
op
ed in
the
late
80’
s.
• A
NSI
sta
nd
ard
sin
ce 1
994.
• C
urr
ent s
tan
dar
ds
allo
w fo
r 16
Gb
ps
per
lin
k.
• A
llow
s fo
r th
ree
dif
fere
nt t
op
olo
gies
:
Poi
nt-t
o-po
int:
2 ad
dre
sses
Arb
itra
ted
loop
(sim
ilar
to to
ken
rin
g): 1
27 a
dd
ress
es
det
erm
inis
tic,
rea
l-ti
me
cap
able
Sw
itch
ed fa
bric
: 224
ad
dre
sses
, man
y to
po
logi
es a
nd
co
ncu
rren
t dat
a lin
ks p
oss
ible
• D
efi n
es O
SI e
qu
ival
ent l
ayer
s u
p to
the
sess
ion
leve
l.
Mo
stly
use
d in
sto
rage
arr
ays,
b
ut a
pp
licab
le to
su
per
-co
mp
ute
rs a
nd
hig
h in
tegr
ity
syst
ems
as w
ell.
536
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
536
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ethe
rnet
/ IE
EE 8
02.3
O
SI r
elat
ion
: PH
Y, M
AC
, MA
C-c
lien
t
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
App
licat
ion
Pres
enta
tion
Sess
ion
Tran
spor
t
Net
wor
k
Dat
a lin
k
Phys
ical
Net
wor
k
Dat
a lin
k
Phys
ical
Use
r da
taU
ser
data
OSI
Net
wor
k La
yers
80
2.3
MA
C
Physic
al m
ed
ium
-in
de
pe
nd
en
t la
ye
r
MA
C C
lien
t
MII
Physic
al m
ed
ium
-d
ep
en
de
nt
laye
rs
MD
I
80
2.3
MA
C
Physic
al m
ed
ium
-in
de
pe
nd
en
t la
ye
r
MA
C C
lien
t
MII
Physic
al m
ed
ium
-d
ep
en
de
nt
laye
rs
MD
I
PH
Y
Lin
k m
ed
ia,
sig
na
l e
nco
din
g,
an
dtr
an
sm
issio
n r
ate
Tra
nsm
issio
n r
ate
MII
= M
ed
ium
-in
de
pe
nd
en
t in
terf
ace
MD
I =
Me
diu
m-d
ep
en
de
nt
inte
rfa
ce
- t
he
lin
k c
on
ne
cto
r
Lin
k
532
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
532
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Net
wor
k pr
otoc
ols
& s
tand
ards
Ap
plic
atio
n
Pres
enta
tio
n
Sess
ion
Tran
spo
rt
Net
wo
rk
Dat
a lin
k
Phys
ical
Ap
ple
Talk
Fili
ng
Pro
toco
l (A
FP)
Ro
uti
ng
Tab
le
Mai
nte
nan
ce P
rot.
IP
Net
wo
rk
Phys
ical
OSI
Tran
spo
rt
Ap
plic
atio
n
TCP/
IPA
pp
leTa
lk
AT
Up
dat
e B
ased
R
ou
tin
g Pr
oto
col
AT
Tran
sact
ion
Pr
oto
col
Nam
e B
ind
ing
Pro
t.A
T Ec
ho
Pr
oto
col
AT
Dat
a St
ream
Pr
oto
col
AT
Sess
ion
Pr
oto
col
Zo
ne
Info
Pr
oto
col
Prin
ter
Acc
ess
Pro
toco
l
Dat
agra
m D
eliv
ery
Pro
toco
l (D
DP)
Ap
ple
Talk
Add
ress
Res
olu
tio
n Pr
oto
col (
AA
RP)
Eth
erTa
lk L
ink
Acc
ess
Pro
toco
lLo
calT
alk
Lin
k A
cces
s Pr
oto
col
Toke
nTa
lk L
ink
Acc
ess
Pro
toco
lFD
DIT
alk
Lin
k A
cces
s Pr
oto
col
IEEE
802
.3Lo
calT
alk
Toke
n R
ing
IEEE
802
.5FD
DI
557
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
557
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
()
()
ab
Ca
Cb
<"
&
Imp
licat
ion
s:
()
()
()
()
()
Ca
Cb
ab
ab
ba
<&
""
0J
z=
()
()
Ca
Cb
ab
ab
ba
&"
"/
JJ
z=
=^
^h
h
()
()
()
Ca
Cb
Cc
ca
<&
"J
=^
h
()
()
()
Ca
Cb
Cc
ca
<<
&"
J^
h
553
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
553
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
[Lam
po
rt 1
978]
()
()
ab
Ca
Cb
<"
&
wit
h a
b"
bei
ng
a ca
usa
l rel
atio
n b
etw
een
a a
nd
b,
and
(
)C
a,
()
Cb
are
the
(vir
tual
) tim
es a
sso
ciat
ed w
ith
a a
nd
b
ab
" if
f:•
a h
app
ens
earl
ier
than
b in
the
sam
e se
qu
enti
al c
on
tro
l-fl
ow
or
• a
den
ote
s th
e se
ndin
g ev
ent o
f mes
sage
m,
wh
ile b
den
ote
s th
e re
ceiv
ing
even
t of t
he
sam
e m
essa
ge m
or
• th
ere
is a
tran
sitiv
e ca
usal
rel
atio
n b
etw
een
a a
nd
b:
ae
eb
n1
""
""
f
No
tio
n o
f co
ncu
rren
cy:
ab
ab
ba
&"
"/
JJ
z^
^h
h
549
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
549
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Sync
hro
nize
a ‘r
eal-
tim
e’ c
lock
(bi-
dir
ecti
ona
l)
Res
etti
ng
the
clo
ck d
rift
by
regu
lar
refe
ren
ce ti
me
re-s
ynch
ron
izat
ion
:
Max
imal
clo
ck d
rift
d d
efi n
ed a
s:
()
()
Ct
Ct
-1
11
21
21
##
dd
++
-t
t-
^^
hh
‘rea
l-ti
me’
clo
ck is
ad
just
ed
forw
ard
s &
bac
kwar
ds
Cal
enda
r ti
me
t 're
al-t
ime'
C 'm
easu
red
tim
e'
syn
c.sy
nc.
syn
c.
ref.
tim
e
ref.
tim
e
ref.
tim
e
real
clo
ck
idea
lcl
ock
545
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
545
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Co
mm
on
des
ign
crit
eria
Ach
ieve
De-
coup
ling
/ hig
h d
egre
e o
f lo
cal a
uto
no
my
Coo
pera
tion
rat
her
than
cen
tral
co
ntr
ol
Co
nsi
der
Rel
iabi
lity
Co
nsi
der
Sca
labi
lity
Co
nsi
der
Per
form
ance
558
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
558
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
()
()
ab
Ca
Cb
<"
&
Imp
licat
ion
s:
()
()
()
()
()
Ca
Cb
ab
ab
ba
<&
""
0J
z=
()
()
Ca
Cb
ab
ab
ba
&"
"/
JJ
z=
=^
^h
h
()
()
()
()
()
Ca
Cb
Cc
ca
ac
ac
<&
""
0J
z=
=^
h
()
()
()
()
()
Ca
Cb
Cc
ca
ac
ac
<<
&"
"0
Jz
=^
h
554
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
554
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
()
()
ab
Ca
Cb
<"
&
Imp
licat
ion
s:
()
()
?C
aC
b<
&
()
()
?C
aC
b&
=
()
()
()
?C
aC
bC
c<
&=
()
()
()
?C
aC
bC
c<
<&
550
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
550
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Sync
hro
nize
a ‘r
eal-
tim
e’ c
lock
(fo
rwar
d o
nly)
Res
etti
ng
the
clo
ck d
rift
by
regu
lar
refe
ren
ce ti
me
re-s
ynch
ron
izat
ion
:
Max
imal
clo
ck d
rift
d d
efi n
ed a
s:
()
()
Ct
Ct
-1
11
21
21
##
d+
-t
t-
^h
‘rea
l-ti
me’
clo
ck is
ad
just
ed
forw
ard
s o
nly
Mon
oton
ic t
ime
t 're
al-t
ime'
C 'm
easu
red
tim
e'
syn
c.sy
nc.
syn
c.
ref.
tim
e
ref.
tim
e
ref.
tim
e
idea
lcl
ock
546
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
546
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Som
e co
mm
on
phe
nom
ena
in d
istr
ibut
ed s
yste
ms
1. U
npre
dict
able
del
ays
(co
mm
un
icat
ion
) A
re w
e d
on
e ye
t?
2. M
issi
ng o
r im
prec
ise
tim
e-ba
se C
ausa
l rel
atio
n o
r te
mp
ora
l rel
atio
n?
3. P
arti
al fa
ilure
s L
ikel
iho
od
of i
nd
ivid
ual
failu
res
incr
ease
s
Lik
elih
oo
d o
f co
mp
lete
failu
re d
ecre
ases
(in
cas
e o
f a g
oo
d d
esig
n)
559
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
559
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
Tim
e as
der
ived
fro
m c
ausa
l rel
atio
ns:
25
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2 P 3
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
Mes
sage
2022
26
22233
24
27
30
4
27
24
29
225
8
222222222225 29292929292929222922229292299999
9
262727272777777777
30
3
2627272727277777
0 2333
31
36
36
31
333333
35
3
35
383733
34333333
3535
443433435
Eve
nts
in c
on
curr
ent c
on
tro
l fl o
ws
are
no
t ord
ered
.
No
glo
bal
ord
er o
f tim
e.
555
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
555
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
()
()
ab
Ca
Cb
<"
&
Imp
licat
ion
s:
()
()
()
Ca
Cb
ba
<&
"J
()
()
Ca
Cb
ab
&z
=
()
()
()
?C
aC
bC
c<
&=
()
()
()
?C
aC
bC
c<
<&
551
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
551
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h sy
nchr
oni
zed
clo
cks
• 6
tim
es:
6 r
ecei
ved
Req
ues
ts: A
dd to
loca
l Req
ues
tQu
eue
(ord
ered
by
tim
e)6
rec
eive
d R
elea
se m
essa
ges:
Del
ete
corr
esp
on
din
g Re
qu
ests
in lo
cal R
equ
estQ
ueu
e
1. C
reat
e O
wn
Req
ues
t an
d a
ttac
h cu
rren
t tim
e-st
amp
.A
dd O
wn
Req
ues
t to
loca
l Req
ues
tQu
eue
(ord
ered
by
tim
e).
Send
Ow
nRe
qu
est t
o a
ll p
roce
sses
.
2. D
elay
by
L2 ( L
bei
ng
the
tim
e it
take
s fo
r a
mes
sage
to r
each
all
net
wo
rk n
od
es)
3. W
hile
To
p (R
equ
estQ
ueu
e) ≠
Ow
nRe
qu
est:
dela
y u
nti
l new
mes
sage
4. E
nter
an
d le
ave
crit
ical
reg
ion
5. S
end
Rele
ase-
mes
sage
to a
ll p
roce
sses
.
547
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
547
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tim
e in
dis
trib
uted
sys
tem
s
Two
alt
ern
ativ
e st
rate
gies
:
Bas
ed o
n a
shar
ed t
ime
Syn
chro
nize
clo
cks!
Bas
ed o
n se
que
nce
of e
vent
s C
reat
e a
virt
ual t
ime!
560
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
560
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Imp
lem
enti
ng a
vir
tual
(lo
gica
l) ti
me
1.
:P
C0
ii
6=
2.
:P
i6 6
loca
l eve
nts
: CC
1i
i=
+;
6 s
end
eve
nts
: CC
1i
i=
+; S
end
(mes
sage
, Ci);
6 r
ecei
ve e
ven
ts: R
ecei
ve (m
essa
ge, C
m);
(,
)m
ax
CC
C1
ii
m=
+;
556
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
556
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Vir
tual
(lo
gica
l) ti
me
()
()
ab
Ca
Cb
<"
&
Imp
licat
ion
s:
()
()
()
()
()
Ca
Cb
ab
ab
ba
<&
""
0J
z=
()
()
Ca
Cb
ab
ab
ba
&"
"/
JJ
z=
=^
^h
h
()
()
()
?C
aC
bC
c<
&=
()
()
()
?C
aC
bC
c<
<&
552
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
552
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h sy
nchr
oni
zed
clo
cks
Ana
lysi
s•
No
dea
dlo
ck, n
o in
div
idu
al s
tarv
atio
n, n
o li
velo
ck.
• M
inim
al r
equ
est d
elay
: L2
.
• M
inim
al r
elea
se d
elay
: L.
• C
om
mu
nic
atio
ns
req
uir
emen
ts p
er r
equ
est:
N2
1-
^h m
essa
ges
(can
be
sign
ifi ca
ntl
y im
pro
ved
by
emp
loyi
ng
bro
adca
st m
ech
anis
ms)
.
• C
lock
dri
fts
affe
ct fa
irn
ess,
bu
t no
t in
tegr
ity
of t
he
crit
ical
reg
ion
.
Ass
um
pti
on
s:
• L
is k
no
wn
an
d c
on
stan
t v
iola
tio
n le
ads
to lo
ss o
f mu
tual
exc
lusi
on
.
• N
o m
essa
ges
are
lost
v
iola
tio
n le
ads
to lo
ss o
f mu
tual
exc
lusi
on
.
548
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
548
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
‘Rea
l-ti
me’
clo
cks
are:
• di
scre
te –
i.e.
tim
e is
no
t den
se a
nd
ther
e is
a m
inim
al g
ran
ula
rity
• dr
ift a
ffec
ted:
Max
imal
clo
ck d
rift
d d
efi n
ed a
s:
()
()
Ct
Ct
-1
11
21
21
##
dd
++
-t
t-
^^
hh
oft
en s
pec
ifi ed
as
PPM
(Par
ts-P
er-M
illio
n)
(typ
ical
20
. P
PM in
co
mp
ute
r ap
plic
atio
ns)
t 're
al-t
ime'
1
1
idea
l clo
ck
d
C 'm
easu
red
tim
e'
1-(1
+d
)-1real
clo
ck
573
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
573
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
22
26
2223
24
27
4
3027
24
29229
22225
8
2222222222225 292929292929292929222922999
39
26272727272277777777
26272727227777777
0
0 233
31
36
36
31
333333
35
3
35
3837
22
21
220
33
343333
3535P 1 P 2P 1
43433435
P 0
3
30
331
0
P 3
0
303033
12
• O
bse
rver
-pro
cess
P0
(an
y p
roce
ss) c
reat
es a
sn
apsh
ot t
oke
n t
s an
d s
aves
its
loca
l sta
te s
0.
• P 0
sen
ds t
s to
all
oth
er p
roce
sses
.
569
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
569
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
A c
on
sist
ent g
lob
al s
tate
(sn
apsh
ot)
is d
efi n
e b
y a
un
iqu
e d
ivis
ion
into
:
• “T
he
Past
” P
(eve
nts
bef
ore
the
snap
sho
t):
()
()
eP
ee
eP
21
21
"&
/!
!
• “T
he
Futu
re”
F (e
ven
ts a
fter
the
snap
sho
t):
()
()
ee
ee
FF
12
12
"&
/!
!
565
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
565
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Elec
ting
a c
entr
al c
oo
rdin
ato
r (t
he B
ully
alg
ori
thm
)A
ny
pro
cess
P w
hic
h n
oti
ces
that
the
cen
tral
co
ord
inat
or
is g
on
e, p
erfo
rms:
1. P
sen
ds a
n E
lect
ion
-mes
sage
to
all
pro
cess
es w
ith
hig
her
pro
cess
nu
mb
ers.
2. P
wai
ts fo
r re
spo
nse
mes
sage
s. I
f no
on
e re
spo
nd
s af
ter
a p
re-d
efin
ed a
mo
un
t of t
ime:
P
dec
lare
s it
self
the
new
co
ord
inat
or
and
sen
ds
ou
t a C
oo
rdin
ato
r-m
essa
ge to
all.
If a
ny
pro
cess
res
po
nd
s,
then
the
elec
tio
n a
ctiv
ity
for
P is
ove
r an
d P
wai
ts fo
r a
Co
ord
inat
or-
mes
sage
All
pro
cess
es P
i per
form
at a
ll ti
mes
:
• If
Pi r
ecei
ves
a El
ecti
on
-mes
sage
fro
m a
pro
cess
wit
h
a lo
wer
pro
cess
nu
mb
er, i
t res
pond
s to
the
ori
gin
atin
g p
roce
ss
and
sta
rts
an e
lect
ion
pro
cess
itse
lf (i
f no
t ru
nn
ing
alre
ady)
.
561
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
561
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h lo
gica
l clo
cks
• 6
tim
es: 6
rec
eive
d R
equ
ests
:
Add
to lo
cal R
equ
estQ
ueu
e (o
rder
ed b
y ti
me)
R
eply
wit
h A
ckn
ow
led
ge o
r O
wn
Req
ues
t
• 6
tim
es: 6
rec
eive
d R
elea
se m
essa
ges:
Del
ete
corr
esp
on
din
g Re
qu
ests
in lo
cal R
equ
estQ
ueu
e
1. C
reat
e O
wn
Req
ues
t an
d a
ttac
h cu
rren
t tim
e-st
amp
.
Add
Ow
nRe
qu
est t
o lo
cal R
equ
estQ
ueu
e (o
rder
ed b
y ti
me)
.
Send
Ow
nRe
qu
est t
o a
ll p
roce
sses
.2.
Wai
t fo
r To
p (R
equ
estQ
ueu
e) =
Ow
nRe
qu
est &
no
ou
tsta
nd
ing
rep
lies
3. E
nter
an
d le
ave
crit
ical
reg
ion
4. S
end
Rele
ase-
mes
sage
to a
ll p
roce
sses
.
574
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
574
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
22
26
2223
24
27
30
4
27
24
29
225
8
222222222225 292292292922229229292929299999
9
26272727227277777777777
26272727272277777
233
6
363
333333
35
3837
33
43433435
P 0
3
220
3030
3130
3
33
313131
P 0
21
220
P 1 P 2
36365
33
34333
55333335533535333333333335303033
12
• P i
6 w
hic
h r
ecei
ve t
s (a
s an
ind
ivid
ual
toke
n-m
essa
ge, o
r as
par
t of a
no
ther
mes
sage
):
• Sa
ve lo
cal s
tate
si a
nd
sen
d s i
to P
0.
• A
ttac
h t s
to a
ll fu
rth
er m
essa
ges,
wh
ich
are
to b
e se
nt t
o o
ther
pro
cess
es.
• Sa
ve t
s an
d ig
nore
all
furt
her
inco
min
g t s
‘s.
570
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
570
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ho
w to
rea
d th
e cu
rren
t sta
te o
f a d
istr
ibu
ted
sys
tem
?
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
2022
26
22233
24
27
30
4
27
24
29
225
8
2222222225 292292929292222922929292299999
9
26272727227277777777777
0
262722727777777
0 2333333333333333333333333333333333333
3434334343433433343343434
31
3135
4437
333333333333333333335
38
35 34
6
333 36
333333333333333333333333333
333533353333335333335353535333533535355555555
P 0
3230
30
30
12
3337 44440
388888
Inst
ead
: so
me
enti
ty p
rob
es a
nd
co
llect
s lo
cal s
tate
s.
Wh
at s
tate
of t
he
glo
bal
sys
tem
has
bee
n a
ccu
mu
late
d?
So
rtin
g th
e ev
ents
into
pas
t an
d fu
ture
eve
nts
.
566
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
566
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ho
w to
rea
d th
e cu
rren
t sta
te o
f a d
istr
ibu
ted
sys
tem
?
25
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2 P 3
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
Mes
sage
2022
26
22233
24
27
30
4
27
24
29
225
8
2222222225 2922929292922229229292929999
9
26272727272277777777777
30
3
262722727777777
0 233
31
36
36
31
3333333
35
3
35
383733
343333
3535
43433435
This
“go
d’s
eye
vie
w”
do
es in
fact
no
t exi
st.
562
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
562
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h lo
gica
l clo
cks
Ana
lysi
s•
No
dea
dlo
ck, n
o in
div
idu
al s
tarv
atio
n, n
o li
velo
ck.
• M
inim
al r
equ
est d
elay
: 1
N-
req
ues
ts (1
bro
adca
st) +
1
N-
rep
lies.
• M
inim
al r
elea
se d
elay
: 1
N-
rele
ase
mes
sage
s (o
r 1
bro
adca
st).
• C
om
mu
nic
atio
ns
req
uir
emen
ts p
er r
equ
est:
N1
3-
^h m
essa
ges
(or
1N
- m
essa
ges
+ 2
bro
adca
sts)
.
• C
lock
s ar
e ke
pt r
ecen
t by
the
exch
ange
d m
essa
ges
them
selv
es.
Ass
um
pti
on
s:
• N
o m
essa
ges
are
lost
v
iola
tio
n le
ads
to s
tall.
575
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
575
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
22
26
2223
24
27
30
4
27
24
29
22225
8
222222222225 292922922929292292929292299999
9
26272727272277777777
26272727222777777
233
6
363
33333
35
3837
33
4343435
P 0
3
220
3030
3130
3
33
313131
P 0
21
220
P 1 P 2
36365
33
3433
55333335333533333333335303033
12
• P i
6 w
hic
h p
revi
ou
sly
rece
ived
ts
and
rec
eive
a m
essa
ge m
wit
ho
ut
t s:
• Fo
rwar
d m
to P
0 (t
his
mes
sage
bel
on
gs to
the
snap
sho
t).
571
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
571
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ho
w to
rea
d th
e cu
rren
t sta
te o
f a d
istr
ibu
ted
sys
tem
?
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
2022
26
2223
24
27
4
3027
24
29
2225
8
2222222222222225 2929292929292222292922922999999
9
262727272722777777777
0
262722727777777
0 233333333333333333333333333333333333
343433433434333433434444
31
3135 37
4444
35
38
35 34
636
33333333333333333333333333333333
333335333353353353333555555555
P 0
3230
30
30
12
337 4440
38888
Inst
ead
: so
me
enti
ty p
rob
es a
nd
co
llect
s lo
cal s
tate
s.
Wh
at s
tate
of t
he
glo
bal
sys
tem
has
bee
n a
ccu
mu
late
d?
Eve
nt i
n th
e p
ast r
ecei
ves
a m
essa
ge fr
om
the
futu
re!
Div
isio
n n
ot p
oss
ible
S
nap
sho
t in
con
sist
ent!
567
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
567
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ho
w to
rea
d th
e cu
rren
t sta
te o
f a d
istr
ibu
ted
sys
tem
?
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
22
26
2223
24
27
30
4
27
24
29
22225
8
2222222225 2929229292922922922922999999
9
26272727272277777777777
262727222777777
638
37
P 0 P 32521
2
P 1 P 220
4440322
33336
333333
3
33
4343343555
33030
3130
3
3
3
33333333333
333131331
303033
12
36
3536
39
37733337373337337373737773
36
6
35
383733
343434334343433434344343433444444337 4440
88388
36
5
3
55
3
353535
Inst
ead
: so
me
enti
ty p
rob
es a
nd
co
llect
s lo
cal s
tate
s.
Wh
at s
tate
of t
he
glo
bal
sys
tem
has
bee
n a
ccu
mu
late
d?
563
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
563
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h a
toke
n ri
ng s
truc
ture
1. O
rgan
ize
all p
roce
sses
in a
logi
cal o
r p
hys
ical
rin
g to
po
logy
2. S
end
on
e to
ken
mes
sage
to o
ne
pro
cess
3. 6
tim
es, 6
pro
cess
es: O
n re
ceiv
ing
the
toke
n m
essa
ge:
1. If
req
uir
ed th
e p
roce
ss
ente
rs a
nd
leav
es a
cri
tica
l sec
tio
n (w
hile
ho
ldin
g th
e to
ken
).2.
Th
e to
ken
is p
asse
d al
on
g to
the
nex
t pro
cess
in th
e ri
ng.
Ass
um
pti
on
s:
• To
ken
is n
ot l
ost
v
iola
tio
n le
ads
to s
tall.
(a lo
st to
ken
can
be
reco
vere
d b
y a
nu
mb
er o
f mea
ns
– e.
g. th
e ‘e
lect
ion
’ sch
eme
follo
win
g)
576
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
576
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
2022
26
2223
24
27
30
4
27
24
P 3P 1 P 2
29
22225
8
22222222222222225 2929292922229292292929229999
9
26272727272277777777
26272727227777777
233
05
363
333333
3837
33
4343345
P 0
3
P 0
3030
3130
3
33
3131
3536
39
73
363
35
3837
5
31
P
55533335333333533333353
34333
6666663
666666636336666666666663636363636636363636336666666333333333333
33333333333
303033
12
• P i
6 w
hic
h r
ecei
ve t
s (a
s an
ind
ivid
ual
toke
n-m
essa
ge, o
r as
par
t of a
no
ther
mes
sage
):
• Sa
ve lo
cal s
tate
si a
nd
sen
d s i
to P
0.
• A
ttac
h t s
to a
ll fu
rth
er m
essa
ges,
wh
ich
are
to b
e se
nt t
o o
ther
pro
cess
es.
• Sa
ve t
s an
d ig
nore
all
furt
her
inco
min
g t s
‘s.
572
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
572
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Snap
sho
t al
gori
thm
• O
bse
rver
-pro
cess
P0
(an
y p
roce
ss) c
reat
es a
sn
apsh
ot t
oke
n t
s an
d s
aves
its
loca
l sta
te s
0.
• P 0
sen
ds t
s to
all
oth
er p
roce
sses
.
• P i
6 w
hic
h r
ecei
ve t
s (a
s an
ind
ivid
ual
toke
n-m
essa
ge, o
r as
par
t of a
no
ther
mes
sage
):
• Sa
ve lo
cal s
tate
si a
nd
sen
d s i
to P
0.
• A
ttac
h t s
to a
ll fu
rth
er m
essa
ges,
wh
ich
are
to b
e se
nt t
o o
ther
pro
cess
es.
• Sa
ve t
s an
d ig
nore
all
furt
her
inco
min
g t s
‘s.
• P i
6 w
hic
h p
revi
ou
sly
rece
ived
ts
and
rec
eive
a m
essa
ge m
wit
ho
ut
t s:
• Fo
rwar
d m
to P
0 (t
his
mes
sage
bel
on
gs to
the
snap
sho
t).
568
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
568
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ho
w to
rea
d th
e cu
rren
t sta
te o
f a d
istr
ibu
ted
sys
tem
?
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 2
3135
36
2324
2526
2730
3133
3435
3637
3031
3233
3435
3637
4038
39
2728
3037
38
2022
26
2223
24
27
30
4
27
24
29
22225
8
222222222222225 2929222292929292292929299999
9
2627272727277777777777
3
262727272777777
0 2333
31
3136
363
3
35
3
35
383733
343333
3535
434435
P 0
33
30
3
3
337 4440
388888
12
31
333333434333335
43
Inst
ead
: so
me
enti
ty p
rob
es a
nd
co
llect
s lo
cal s
tate
s.
Wh
at s
tate
of t
he
glo
bal
sys
tem
has
bee
n a
ccu
mu
late
d?
Co
nn
ecti
ng
all t
he
stat
es to
a g
lob
al s
tate
.
564
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
564
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
cri
tica
l reg
ions
wit
h a
cent
ral c
oo
rdin
ato
r
A g
lob
al, s
tati
c, c
entr
al c
oo
rdin
ato
r In
valid
ates
the
idea
of a
dis
trib
ute
d s
yste
m
En
able
s a
very
sim
ple
mu
tual
exc
lusi
on
sch
eme
Ther
efo
re:
• A
glo
bal
, cen
tral
co
ord
inat
or
is e
mp
loye
d in
so
me
syst
ems
… y
et …
• …
if it
fails
, a s
yste
m to
co
me
up
wit
h a
new
co
ord
inat
or
is p
rovi
ded
.
589
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
589
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
or
acce
pt C
onte
ntio
n (P
rint
_Job
: i
n Jo
b_Ty
pe;
Serv
er_I
d : in
Tas
k_Id
) do
i
f Pr
int_
Job in A
ppli
edFo
rJob
s th
en
if S
erve
r_Id
= C
urre
nt_T
ask
then
Int
erna
l_Pr
int_
Serv
er.S
tart
_Pri
nt (
Prin
t_Jo
b);
el
sif
Serv
er_I
d >
Curr
ent_
Task
the
n
I
nter
nal_
Prin
t_Se
rver
.Can
cel_
Prin
t (P
rint
_Job
);
N
ext_
Serv
er_O
n_Ri
ng.C
onte
ntio
n (P
rint
_Job
; Se
rver
_Id)
;
el
se
n
ull;
--
remo
ving
the
con
tent
ion
mess
age
from
rin
g
end
if;
e
lse
Tu
rned
_Dow
n_Jo
bs :
= Tu
rned
_Dow
n_Jo
bs +
Pri
nt_J
ob;
Ne
xt_S
erve
r_On
_Rin
g.Co
nten
tion (
Prin
t_Jo
b; S
erve
r_Id
);
end
if;
end
Cont
enti
on;
or
term
inat
e;
e
nd s
elec
t;
end
loop
;
end
Pri
nt_S
erve
r;
585
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
585
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
erve
r
Serv
er
Serv
erer
ver
ver
Serv
er
Serv
eerr
SS
ver
Ser
Se
Serv Se
rver
rver
Clie
nt
581
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
581
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Co
nsis
tent
dis
trib
uted
sta
tes
Wh
y w
ou
ld w
e n
eed
that
?
• Fi
nd
dea
dlo
cks.
• Fi
nd
term
inat
ion
/ co
mp
leti
on
co
nd
itio
ns.
• …
an
y o
ther
glo
bal
saf
ety
of l
iven
ess
pro
per
ty.
• C
olle
ct a
co
nsi
sten
t sys
tem
sta
te fo
r sy
stem
bac
kup
/res
tore
.
• C
olle
ct a
co
nsi
sten
t sys
tem
sta
te fo
r fu
rth
er p
ro-
cess
ing
(e.g
. dis
trib
ute
d d
atab
ases
).
• …
577
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
577
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 223
2425
2635
3637 40
3839
2728
3738
0
244
27
24
29
22225
8
29292229292929229222999999222222222225
9
2626
P25
2P 2 P 3
2022
26
2223
38
P 0
3536
39
73
35
38328
2721
P 1P 0012
• Sa
ve t
s an
d ig
nore
all
furt
her
inco
min
g t s
‘s.
590
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
590
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ions
Co
ncu
rren
cy a
nd
dis
trib
uti
on
in s
yste
ms
wit
h m
ult
iple
, in
terd
epen
den
t in
tera
ctio
ns?
Co
ncu
rren
t an
d d
istr
ibu
ted
clie
nt/
serv
er in
tera
ctio
ns
bey
on
d s
ingl
e re
mo
te p
roce
du
re c
alls
?
586
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
586
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
ntJob
_Co
mp
lete
d (R
esu
lts)
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
ntJob
_Co
mp
lete
d (R
esu
lts)
582
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
582
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)
Serv
erC
lien
tSe
rver
Clie
nt
578
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
578
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 223
2425
2627
37
3031
40
2728
38
2022
6
22
P 1
2324
27
25
5
2630
4
27
24
29
225
8
22222222225 2922929292922229229292929999
9
262722722722727777777777777
26272272772277777
P 1P 0 PPP
3337 44440P 3
2
1 P 2 PP PP
0
388388
12
• Fi
naliz
e sn
apsh
ot
591
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
591
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ions
Defi
nit
ion
(AC
ID p
rop
erti
es):
• A
tom
icit
y: A
ll o
r no
ne o
f th
e su
b-o
per
atio
ns
are
perf
orm
ed.
Ato
mic
ity
hel
ps
ach
ieve
cra
sh r
esili
ence
. If a
cra
sh o
ccu
rs, t
hen
it is
po
ssib
le
to r
oll
bac
k th
e sy
stem
to th
e st
ate
bef
ore
the
tran
sact
ion
was
invo
ked
.
• C
onsi
sten
cy: T
ran
sfo
rms
the
syst
em fr
om
on
e co
nsis
tent
sta
te to
an
oth
er c
onsi
sten
t sta
te.
• Is
olat
ion:
Res
ult
s (i
ncl
ud
ing
par
tial
res
ult
s) a
re n
ot r
evea
led
unle
ss a
nd
unt
il th
e tr
ansa
ctio
n co
mm
its.
If th
e o
per
atio
n a
cces
ses
a sh
ared
dat
a o
bje
ct,
invo
cati
on
do
es n
ot i
nte
rfer
e w
ith
oth
er o
per
atio
ns
on
the
sam
e o
bje
ct.
• D
urab
ility
: Aft
er a
co
mm
it, r
esu
lts
are
guar
ante
ed t
o pe
rsis
t, ev
en a
fter
a s
ub
seq
uen
t sys
tem
failu
re.
587
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
587
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)wi
th A
da.T
ask_
Iden
tifi
cati
on; us
e Ad
a.Ta
sk_I
dent
ific
atio
n;
task typ
e Pr
int_
Serv
er is
ent
ry S
end_
To_S
erve
r (P
rint
_Job
: i
n Jo
b_Ty
pe;
Job_
Done
:
out
Bool
ean)
;
ent
ry C
onte
ntio
n
(P
rint
_Job
: i
n Jo
b_Ty
pe;
Serv
er_I
d :
in
Task
_Id)
;
end Pr
int_
Serv
er;
583
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
583
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Rin
g o
f ser
vers
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Rin
g o
f ser
vers
579
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
579
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
sta
tes
Ru
nn
ing
the
snap
sho
t alg
ori
thm
:
P 325
tim
e0
510
1520
2530
3540
45
21
20
P 1
2627
29
22
29
P 223
2425
2627
30
3031
32
2728
30
26
2324
27
4
3027
24
29
22225
8
292922929292292292292299999922222222225
9
26272727272277777777777
2627277277777
P 0
1 2202222
1 P 3P 2P
2P 1P 0
32233030
30
3
3
0
303033
12
So
rtin
g th
e ev
ents
into
pas
t an
d fu
ture
eve
nts
.
Pas
t an
d fu
ture
eve
nts
un
iqu
ely
sep
arat
ed
Co
nsi
sten
t sta
te
592
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
592
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ions
Defi
nit
ion
(AC
ID p
rop
erti
es):
• A
tom
icit
y: A
ll o
r no
ne o
f th
e su
b-o
per
atio
ns
are
perf
orm
ed.
Ato
mic
ity
hel
ps
ach
ieve
cra
sh r
esili
ence
. If a
cra
sh o
ccu
rs, t
hen
it is
po
ssib
le
to r
oll
bac
k th
e sy
stem
to th
e st
ate
bef
ore
the
tran
sact
ion
was
invo
ked
.
• C
onsi
sten
cy: T
ran
sfo
rms
the
syst
em fr
om
on
e co
nsis
tent
sta
te to
an
oth
er c
onsi
sten
t sta
te.
• Is
olat
ion:
Res
ult
s (i
ncl
ud
ing
par
tial
res
ult
s) a
re n
ot r
evea
led
unle
ss a
nd
unt
il th
e tr
ansa
ctio
n co
mm
its.
If th
e o
per
atio
n a
cces
ses
a sh
ared
dat
a o
bje
ct,
invo
cati
on
do
es n
ot i
nte
rfer
e w
ith
oth
er o
per
atio
ns
on
the
sam
e o
bje
ct.
• D
urab
ility
: Aft
er a
co
mm
it, r
esu
lts
are
guar
ante
ed t
o pe
rsis
t, ev
en a
fter
a s
ub
seq
uen
t sys
tem
failu
re.
isp
oss
ible
Ho
w to
en
sure
co
nsi
sten
cy
in a
dis
trib
ute
d s
yste
m?
Act
ual
iso
lati
on
an
d
effi
cien
t co
ncu
rren
cy?
Shad
ow
co
pie
s?
Act
ual
iso
lati
on
or
the
app
eara
nce
of i
sola
tio
n?
sub
op
erat
ion
sar
epe
rfor
med
Ato
mic
op
erat
ion
s sp
ann
ing
mu
ltip
le p
roce
sses
?
Wh
at h
ard
war
e d
o w
e
nee
d to
ass
um
e?
588
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
588
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)ta
sk b
ody Pr
int_
Serv
er i
s
beg
in
lo
op
s
elec
t
ac
cept Sen
d_To
_Ser
ver (P
rint
_Job
: in Jo
b_Ty
pe; Jo
b_Do
ne : out
Boo
lean
) do
i
f no
t Pr
int_
Job
in T
urne
d_Do
wn_J
obs
then
if
Not
_Too
_Bus
y th
en
A
ppli
ed_F
or_J
obs
:= A
ppli
ed_F
or_J
obs
+ Pr
int_
Job;
Nex
t_Se
rver
_On_
Ring
.Con
tent
ion
(Pri
nt_J
ob,
Curr
ent_
Task
);
r
eque
ue I
nter
nal_
Prin
t_Se
rver
.Pri
nt_J
ob_Q
ueue
;
el
se
T
urne
d_Do
wn_J
obs
:= T
urne
d_Do
wn_J
obs
+ Pr
int_
Job;
en
d if
;
e
nd i
f;
en
d Se
nd_T
o_Se
rver
;
(...)
584
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
584
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
A d
istr
ibut
ed s
erve
r (lo
ad b
alan
cing
)
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Sen
d_T
o_G
rou
p (J
ob
)Se
rver
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Sen
d_T
o_G
rou
p (J
TTo
b)
580
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
580
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Snap
sho
t al
gori
thm
Term
inat
ion
cond
itio
n?
Eith
er • M
ake
assu
mp
tio
ns
abo
ut t
he
com
mu
nic
atio
n d
elay
s in
the
syst
em.
or
• C
ou
nt t
he
sen
t an
d r
ecei
ved
mes
sage
s fo
r ea
ch p
roce
ss (i
ncl
ud
e th
is in
the
lo-
cal s
tate
) an
d k
eep
trac
k o
f ou
tsta
nd
ing
mes
sage
s in
the
ob
serv
er p
roce
ss.
605
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
605
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
Rea
d (C
)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
R WeaR
e
Re
W
P 1P 2
P 3
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
Ser
ializ
atio
n g
rap
h is
cyc
lic.
No
t ser
ializ
able
601
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
601
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
Re
Re
W
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
• Th
e o
rder
bet
wee
n p
roce
sses
als
o le
ads
to a
glo
bal
ord
er o
f pro
cess
es.
Ser
ializ
able
597
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
597
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Wri
te (
B)
ead
(A)
(A)
(A)
AA)
AAAAA)))))
WR
P 1P 2
Ser
ializ
able
593
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
593
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ions
A c
lose
r lo
ok
insi
de
tran
sact
ion
s:
• Tr
ansa
ctio
ns c
on
sist
of a
seq
uen
ce o
f ope
rati
ons.
• If
two
op
erat
ion
s o
ut o
f tw
o tr
ansa
ctio
ns
can
be
per
form
ed in
an
y o
rder
wit
h th
e sa
me
fi n
al e
ffec
t, th
ey a
re c
omm
utat
ive
and
no
t cri
tica
l fo
r o
ur
pu
rpo
ses.
• Id
empo
tent
an
d s
ide-
effe
ct fr
ee o
per
atio
ns
are
by
defi
nit
ion
co
mm
uta
tive
.
• A
ll n
on
-co
mm
uta
tive
op
erat
ion
s ar
e co
nsi
der
ed c
riti
cal o
pera
tion
s.
• Tw
o c
riti
cal o
per
atio
ns
as p
art o
f tw
o d
iffe
ren
t tra
nsa
ctio
ns
wh
ile
affe
ctin
g th
e sa
me
ob
ject
are
cal
led
a c
onfl
icti
ng p
air
of o
pera
tion
s.
606
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
606
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ion
sche
dul
ers
Thre
e m
ajo
r d
esig
ns:
• Lo
ckin
g m
etho
ds:
Imp
ose
str
ict m
utu
al e
xclu
sio
n o
n a
ll cr
itic
al s
ecti
on
s.
• Ti
me-
stam
p or
deri
ng:
No
te r
elat
ive
star
tin
g ti
mes
an
d k
eep
ord
er d
epen
den
cies
co
nsi
sten
t.
• “O
ptim
isti
c” m
etho
ds:
Go
ah
ead
un
til a
co
nfl
ict i
s o
bse
rved
– th
en r
oll
bac
k.
602
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
602
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
Rea
d (C
)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
R WeaR
e
Re
W
P 1P 2
P 3
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
• Th
e o
rder
bet
wee
n p
roce
sses
do
es n
o lo
nge
r lea
d to
a g
lob
al o
rder
of p
roce
sses
.
No
t ser
ializ
able
598
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
598
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)W
rite
(B)
P 2 P 3
Wri
te (
B)
Ord
er
Re
W
P 1P 2
• Tw
o c
on
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h d
iffe
ren
t ord
ers
of e
xecu
tio
ns.
No
t ser
ializ
able
.
594
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
594
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ions
A c
lose
r lo
ok
at m
ult
iple
tran
sact
ion
s:
• A
ny
seq
uen
tial
exe
cuti
on
of m
ult
iple
tran
sact
ion
s w
ill fu
lfi l t
he
AC
ID-p
rop
erti
es, b
y d
efi n
itio
n o
f a s
ingl
e tr
ansa
ctio
n.
• A
co
ncu
rren
t exe
cuti
on
(or ‘
inte
rlea
vin
gs’)
of m
ult
iple
tran
sact
ion
s m
igh
t fu
lfi l t
he
AC
ID-p
rop
erti
es.
If a
sp
ecifi
c co
ncu
rren
t exe
cuti
on
can
be
sho
wn
to b
e eq
uiv
alen
t to
a s
pec
ifi c
seq
uen
tial
ex
ecu
tio
n o
f th
e in
volv
ed tr
ansa
ctio
ns
then
this
sp
ecifi
c in
terl
eavi
ng
is c
alle
d ‘s
eria
lizab
le’.
If a
co
ncu
rren
t exe
cuti
on
(‘in
terl
eavi
ng’
) en
sure
s th
at n
o tr
ansa
ctio
n e
ver
enco
un
ters
an
inco
nsi
sten
t sta
te th
en it
is s
aid
to e
nsu
re th
e ap
pear
ance
of i
sola
tion
.
607
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
607
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ion
sche
dul
ers
– Lo
ckin
g m
etho
ds
Lock
ing
met
ho
ds
incl
ud
e th
e p
oss
ibili
ty o
f dea
dlo
cks
car
efu
l fro
m h
ere
on
ou
t …
• C
ompl
ete
reso
urce
allo
cati
on b
efo
re th
e st
art a
nd
rel
ease
at t
he
end
of e
very
tran
sact
ion
:
Th
is w
ill im
po
se a
str
ict s
equ
enti
al e
xecu
tio
n o
f all
crit
ical
tran
sact
ion
s.
• (S
tric
t) t
wo-
phas
e lo
ckin
g:Ea
ch tr
ansa
ctio
n fo
llow
s th
e fo
llow
ing
two
ph
ase
pat
tern
du
rin
g it
s o
per
atio
n:
• G
row
ing
ph
ase:
lock
s ca
n b
e ac
qu
ired
, bu
t no
t rel
ease
d.
• Sh
rin
kin
g p
has
e: lo
cks
can
be
rele
ased
an
ytim
e, b
ut n
ot a
cqu
ired
(tw
o p
has
e lo
ckin
g)
or
lock
s ar
e re
leas
ed o
n c
om
mit
on
ly (s
tric
t tw
o p
has
e lo
ckin
g).
Po
ssib
le d
ead
lock
s
Ser
ializ
able
inte
rlea
vin
gs
Str
ict i
sola
tio
n (i
n c
ase
of s
tric
t tw
o-p
has
e lo
ckin
g)
• Se
man
tic
lock
ing:
Allo
w fo
r se
par
ate
read
-on
ly a
nd
wri
te-l
ock
s
Hig
her
leve
l of c
on
curr
ency
(see
als
o: u
se o
f fu
nct
ion
s in
pro
tect
ed o
bje
cts)
603
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
603
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Ach
ievi
ng s
eria
lizab
ility
Fo
r th
e se
rial
izab
ility
of t
wo
tran
sact
ion
s it
is n
eces
sary
an
d s
uffi
cien
t fo
r th
e o
rder
of t
hei
r in
voca
tio
ns
of a
ll co
nfl
icti
ng
pai
rs o
f op
erat
ion
s to
be
the
sam
e fo
r all
the
ob
ject
s w
hic
h a
re in
voke
d b
y b
oth
tran
sact
ion
s.
• D
efi n
e: S
eria
lizat
ion
grap
h: A
dir
ecte
d g
rap
h;
Ver
tice
s i r
epre
sen
t tra
nsa
ctio
ns
Ti;
Edge
s T
Ti
j"
rep
rese
nt a
n e
stab
lish
ed g
lob
al o
rder
dep
end
ency
bet
wee
n a
ll co
nfl
icti
ng
pai
rs o
f op
erat
ion
s o
f th
ose
two
tran
sact
ion
s.
Fo
r th
e se
rial
izab
ility
of m
ult
iple
tran
sact
ion
s it
is
nece
ssar
y an
d s
uffi
cien
t th
at th
e se
rial
izat
ion
gra
ph
is a
cycl
ic.
599
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
599
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
Re
Re
W
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
• Th
e o
rder
bet
wee
n p
roce
sses
als
o le
ads
to a
glo
bal
ord
er o
f pro
cess
es.
595
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
595
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Ach
ievi
ng s
eria
lizab
ility
Fo
r th
e se
rial
izab
ility
of t
wo
tran
sact
ion
s it
is n
eces
sary
an
d s
uffi
cien
t fo
r th
e o
rder
of t
hei
r in
voca
tio
ns
of a
ll co
nfl
icti
ng
pai
rs o
f op
erat
ion
s to
be
the
sam
e fo
r all
the
ob
ject
s w
hic
h a
re in
voke
d b
y b
oth
tran
sact
ion
s.
(Det
erm
inin
g o
rder
in d
istr
ibu
ted
sys
tem
s re
qu
ires
logi
cal c
lock
s.)
608
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
608
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ion
sche
dul
ers
– Ti
me
stam
p o
rder
ing
Ad
d a
un
iqu
e ti
me-
stam
p (a
ny
glo
bal
ord
er c
rite
rio
n) o
n e
very
tran
sact
ion
up
on
sta
rt.
Each
invo
lved
ob
ject
can
insp
ect t
he
tim
e-st
amp
s o
f all
req
ues
tin
g tr
ansa
ctio
ns.
• C
ase
1: A
tran
sact
ion
wit
h a
tim
e-st
amp
late
r th
an a
ll cu
rren
tly
acti
ve tr
ansa
ctio
ns
app
lies:
th
e re
qu
est i
s ac
cep
ted
an
d th
e tr
ansa
ctio
n c
an g
o ah
ead.
• A
lter
nat
ive
case
1 (s
tric
t tim
e-st
amp
ord
erin
g):
the
req
ues
t is
dela
yed
un
til t
he
curr
entl
y ac
tive
ear
lier
tran
sact
ion
has
co
mm
itte
d.
• C
ase
2: A
tran
sact
ion
wit
h a
tim
e-st
amp
ear
lier t
han
all
curr
entl
y ac
tive
tran
sact
ion
s ap
plie
s: th
e re
qu
est i
s n
ot a
ccep
ted
an
d th
e ap
ply
ing
tran
sact
ion
is to
be
abor
ted.
Co
llisi
on
det
ecti
on
rat
her
than
co
llisi
on
avo
idan
ce
No
iso
lati
on
C
asca
din
g ab
ort
s p
oss
ible
.
Sim
ple
imp
lem
enta
tio
n, h
igh
deg
ree
of c
on
curr
ency
– al
so in
a d
istr
ibu
ted
en
viro
nm
ent,
as lo
ng
as a
glo
bal
eve
nt o
rder
(tim
e) c
an b
e su
pp
lied
.
604
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
604
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
Wri
te (
B)ea
d (C
)W
rite
(A
)RR
eR
ead
(A)
d(A
)d
(A)
(A)
(A(A(A(A(A)
((A)
A)
AA)
A)
A)
AA)
A)))
WR
P 1P 2
P 3
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
Ser
ializ
atio
n g
rap
h is
acy
clic
.
Ser
ializ
able
600
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
600
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Rea
d (C
)
Ord
er
Wri
te (
B)ea
d (C
)W
rite
(A
)RR
e
ead
(A)
d(A
)d
(A)
d(A
)(A
)(A
)(A(A(A(A
)(A(A
)AA
)A
)A
)A
)A
)))W
R
P 1P 2
P 3
• Th
ree
con
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
(p
air-
wis
e b
etw
een
pro
cess
es).
• Th
e o
rder
bet
wee
n p
roce
sses
als
o le
ads
to a
glo
bal
ord
er o
f pro
cess
es.
Ser
ializ
able
596
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
596
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Seri
aliz
abili
ty
tim
e0
510
1520
2530
3540
45
Wri
te (
A)
P 1
Wri
te (
C)
Rea
d (A
)
Wri
te (
B)
P 2 P 3
Wri
te (
B)
Ord
er
Re
W
• Tw
o c
on
fl ic
tin
g p
airs
of o
per
atio
ns
wit
h th
e sa
me
ord
er o
f exe
cuti
on
.
621
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
621
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
2: I
mpl
emen
t re
sult
s
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
1of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Ever
ybo
dy
des
tro
ys
shad
ow
s
617
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
617
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
7of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Setu
p &
Sta
rt
op
erat
ion
s
Shad
ow
co
py
613
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
613
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
3of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
erve
r
Serv
erSe
rver
erve
r
erve
r
ver
Clie
nt
Seer
eSe
rSe
Serv
erSe
Se
Se
Se
rver
Ser
SSSv
Se
rver
Serer
erve
Se
ver
ver
rv
rver
erve
rver
Dis
trib
ute
d
Tran
sact
ion
609
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
609
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ion
sche
dul
ers
– O
pti
mis
tic
cont
rol
Thre
e se
qu
enti
al p
has
es:
1. R
ead
& e
xecu
te:
Cre
ate
a sh
adow
cop
y o
f all
invo
lved
ob
ject
s an
d
perf
orm
all
req
uir
ed o
per
atio
ns
on
the
shad
ow
co
py
and
loca
lly (i
.e. i
n is
ola
tio
n).
2. V
alid
ate:
Aft
er lo
cal c
om
mit
, che
ck a
ll o
ccu
rred
inte
rlea
vin
gs fo
r se
rial
izab
ility
.
3. U
pdat
e or
abo
rt:
3a. I
f ser
ializ
abili
ty c
ou
ld b
e en
sure
d in
ste
p 2
then
all
resu
lts
of i
nvo
lved
tran
sact
ion
s ar
e w
ritt
en to
all
invo
lved
ob
ject
s –
in d
epen
den
cy o
rder
of t
he
tran
sact
ion
s.
3b. O
ther
wis
e: d
estr
oy s
had
ow
co
pie
s an
d s
tart
ove
r w
ith
the
faile
d tr
ansa
ctio
ns.
622
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
622
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
2: I
mpl
emen
t re
sult
s
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
2of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Ever
ybo
dy
rep
ort
s "C
om
mit
ted
"
618
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
618
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
1: D
eter
min
e re
sult
sta
te
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
8of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Co
ord
inat
or
req
ues
ts
and
ass
emb
les
vote
s:"C
om
mit
" o
r "A
bo
rt"
614
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
614
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
4of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
ver
rver
rver
ver
rver
Det
erm
ine
coo
rdin
ato
r
610
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
610
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Tran
sact
ion
sche
dul
ers
– O
pti
mis
tic
cont
rol
Thre
e se
qu
enti
al p
has
es:
1. R
ead
& e
xecu
te:
Cre
ate
a sh
adow
cop
y o
f all
invo
lved
ob
ject
s an
d
perf
orm
all
req
uir
ed o
per
atio
ns
on
the
shad
ow
co
py
and
loca
lly (i
.e. i
n is
ola
tio
n).
2. V
alid
ate:
Aft
er lo
cal c
om
mit
, che
ck a
ll o
ccu
rred
inte
rlea
vin
gs fo
r se
rial
izab
ility
.
3. U
pdat
e or
abo
rt:
3a. I
f ser
ializ
abili
ty c
ou
ld b
e en
sure
d in
ste
p 2
then
all
resu
lts
of i
nvo
lved
tran
sact
ion
s ar
e w
ritt
en to
all
invo
lved
ob
ject
s –
in d
epen
den
cy o
rder
of t
he
tran
sact
ion
s.
3b. O
ther
wis
e: d
estr
oy s
had
ow
co
pie
s an
d s
tart
ove
r w
ith
the
faile
d tr
ansa
ctio
ns.
Ho
w to
cre
ate
a co
nsi
sten
t co
py? re
sult
s o
f in
volv
ed tr
ansa
ctio
ns
ltfi
ld
tti
Ho
w to
up
dat
e al
l ob
ject
s co
nsi
sten
tly?
(ie
inis
ola
tio
n)
Full
iso
lati
on
an
d
max
imal
co
ncu
rren
cy!
Ab
ort
s h
app
en a
fter
eve
ryth
ing
has
bee
n c
om
mit
ted
loca
lly.
623
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
623
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lor
Pha
se 2
: Glo
bal r
oll b
ack
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
3of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Co
ord
inat
or
inst
ruct
s ev
eryb
od
y to
"A
bo
rt"
619
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
619
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
2: I
mpl
emen
t re
sult
s
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
9of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Co
ord
inat
or
inst
ruct
s ev
eryb
od
y to
"C
om
mit
"
615
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
615
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
5of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Det
erm
ine
coo
rdin
ato
r
611
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
611
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
tra
nsac
tio
n sc
hed
uler
sTh
ree
maj
or
des
ign
s:
• Lo
ckin
g m
etho
ds:
no
ab
ort
sIm
po
se s
tric
t mu
tual
exc
lusi
on
on
all
crit
ical
sec
tio
ns.
• Ti
me-
stam
p or
deri
ng:
po
ten
tial
ab
ort
s al
on
g th
e w
ayN
ote
rel
ativ
e st
arti
ng
tim
es a
nd
kee
p o
rder
dep
end
enci
es c
on
sist
ent.
• “O
ptim
isti
c” m
etho
ds:
ab
ort
s o
r co
mm
its
at th
e ve
ry e
nd
Go
ah
ead
un
til a
co
nfl
ict i
s o
bse
rved
– th
en r
oll
bac
k.
Ho
w to
imp
lem
ent “
com
mit
” an
d “
abo
rt”
op
erat
ion
sin
a d
istr
ibu
ted
en
viro
nm
ent?
624
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
624
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lor
Pha
se 2
: Glo
bal r
oll b
ack
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
4of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Ever
ybo
dy
des
tro
ys
shad
ow
s
620
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
620
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
2: I
mpl
emen
t re
sult
s
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
0of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Ser
ver
Serv
er
Serv
er
Serv
er
Clie
nt
Ser
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
Ever
ybo
dy
com
mit
s
616
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
616
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
6of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
ver
rver
rver
ver
rver
Setu
p &
Sta
rt
op
erat
ion
s
612
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
612
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lSt
art
up (
init
ializ
atio
n) p
hase
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge61
2of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
ver
rver
rver
ver
rver
Rin
g o
f ser
vers
Dat
a
637
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
637
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Co
ord
inat
or
pro
cess
es
hl
lf
hb
d”
pp
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Co
ord
inat
or
also
re
ceiv
ed tw
o m
essa
ges
and
pro
cess
es jo
b
633
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
633
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Dis
trib
ute
job
hl
lf
hb
d”
j
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Co
ord
inat
or
sen
ds
job
bo
th w
ays
629
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
629
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Star
t-u
p (i
nit
ializ
atio
n) p
has
e
hl
lf
hb
d”
p(
)pp
p
Serv
er
Serv
er
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er
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er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Rin
g o
f id
enti
cal
serv
ers
625
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
625
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Two
pha
se c
om
mit
pro
toco
lPh
ase
2: R
epor
t re
sult
of d
istr
ibut
ed t
rans
acti
on
Uw
eR
Zim
mer
The
Aus
tral
ian
Nat
iona
lUni
vers
itypa
ge62
5of
y75
7(c
hapt
er8:
“Dis
trib
uted
Syst
ems”
upto
pa7
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er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
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er
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nt
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Serv
er
Clie
n
Co
ord
.
ver
rver
rver
Serv
erServ
er
nt
C
ver
rver
Co
ord
inat
or
rep
ort
s to
clie
nt:
"Co
mm
itte
d"
or
"Ab
ort
ed"
638
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
638
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Res
ult
del
iver
y
hl
lf
hb
d
yy
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Serv
erServ
er
nt
C
Co
ord
inat
or
del
iver
s h
is lo
cal r
esu
lt
634
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
634
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Dis
trib
ute
job
hl
lf
hb
d
j
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Ever
ybo
dy
rece
ived
job
(b
ut n
ob
od
y kn
ow
s th
at)
630
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
630
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Star
t-u
p (i
nit
ializ
atio
n) p
has
e
hl
lf
hb
d
p(
)pp
p
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Det
erm
ine
coo
rdin
ato
r
626
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
626
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Dis
trib
uted
tra
nsac
tio
n sc
hed
uler
sEv
alu
atin
g th
e th
ree
maj
or
des
ign
met
ho
ds
in a
dis
trib
ute
d e
nvi
ron
men
t:
• Lo
ckin
g m
etho
ds:
No
ab
ort
s.La
rge
ove
rhea
ds;
Dea
dlo
ck d
etec
tio
n/p
reve
nti
on
req
uir
ed.
• Ti
me-
stam
p or
deri
ng:
Po
ten
tial
ab
ort
s al
on
g th
e w
ay.
Rec
om
men
ds
itse
lf fo
r d
istr
ibu
ted
ap
plic
atio
ns,
sin
ce d
ecis
ion
s ar
e ta
ken
loca
lly a
nd
co
mm
un
icat
ion
ove
rhea
d is
rel
ativ
ely
smal
l.
• “O
ptim
isti
c” m
etho
ds:
Ab
ort
s o
r co
mm
its
at th
e ve
ry e
nd
.M
axim
izes
co
ncu
rren
cy, b
ut a
lso
dat
a re
plic
atio
n.
Sid
e-as
pec
t “d
ata
rep
licat
ion
”: la
rge
bo
dy
of l
iter
atu
re o
n th
is to
pic
(s
ee: d
istr
ibu
ted
dat
a-b
ases
/ o
per
atin
g sy
stem
s / s
har
ed m
emo
ry /
cach
e m
anag
emen
t, …
)
639
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
639
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Even
t: Se
rver
cra
sh, n
ew s
erve
rs jo
inin
g, o
r cu
rren
t ser
vers
leav
ing.
Ser
ver
re-c
on
fi gu
rati
on
is tr
igge
red
by
a m
essa
ge to
all
(th
is is
ass
um
ed to
be
sup
po
rted
by
the
dis
trib
ute
d o
per
atin
g sy
stem
).
Each
ser
ver
on
rec
epti
on
of a
re-
con
fi gu
rati
on
mes
sage
:
1. W
ait f
or
loca
l jo
b to
co
mp
lete
or
tim
e-o
ut.
2. S
tore
loca
l co
nsi
sten
t sta
te S
i.
3. R
e-o
rgan
ize
serv
er r
ing,
sen
d lo
cal s
tate
aro
un
d th
e ri
ng.
4. I
f a s
tate
Sj w
ith
ji
> is
rec
eive
d th
en S
Si
j%
5. E
lect
co
ord
inat
or
6. E
nte
r ‘C
oo
rdin
ato
r-’ o
r ‘R
eplic
ate-
mo
de’
635
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
635
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Pro
cess
ing
star
ts
hl
lf
hb
d
gg
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Firs
t ser
ver
det
ects
tw
o jo
b-m
essa
ges
☞ p
roce
sses
job
631
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
631
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Star
t-u
p (i
nit
ializ
atio
n) p
has
e
hl
lf
hb
d
p(
)pp
p
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Co
ord
inat
or
det
erm
ined
627
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
627
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Prem
ise:
A c
rash
ing
serv
er c
om
pu
ter
sho
uld
no
t co
mp
rom
ise
the
fun
ctio
nal
ity
of t
he
syst
em(f
ull
fau
lt to
lera
nce
)A
ssu
mp
tio
ns
& M
ean
s:
• k
com
pu
ters
insi
de
the
serv
er c
lust
er m
igh
t cra
sh w
ith
ou
t lo
sin
g fu
nct
ion
alit
y.
Rep
licat
ion
: at l
east
k1
+ s
erve
rs.
• Th
e se
rver
clu
ster
can
reo
rgan
ize
any
tim
e (a
nd
sp
ecifi
cally
aft
er th
e lo
ss o
f a c
om
pu
ter)
.
Ho
t sta
nd
-by
com
po
nen
ts, d
ynam
ic s
erve
r gr
ou
p m
anag
emen
t.
• Th
e se
rver
is d
escr
ibed
fully
by
the
curr
ent s
tate
an
d th
e se
qu
ence
of m
essa
ges
rece
ived
.
Sta
te m
ach
ines
: we
hav
e to
imp
lem
ent c
on
sist
ent s
tate
ad
just
men
ts (r
e-o
rgan
izat
ion
) an
d c
on
sist
ent m
essa
ge p
assi
ng
(ord
er n
eed
s to
be
pre
serv
ed).
[Sch
nei
der
1990
]
640
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
640
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Sum
mar
y
Dis
trib
uted
Sys
tem
s
• N
etw
orks
• O
SI, t
op
olo
gies
• Pr
acti
cal n
etw
ork
sta
nd
ard
s
• Ti
me
• Sy
nch
ron
ized
clo
cks,
vir
tual
(lo
gica
l) ti
mes
• D
istr
ibu
ted
cri
tica
l reg
ion
s (s
ynch
ron
ized
, lo
gica
l, to
ken
rin
g)
• D
istr
ibut
ed s
yste
ms
• El
ecti
on
s
• D
istr
ibu
ted
sta
tes,
co
nsi
sten
t sn
apsh
ots
• D
istr
ibu
ted
ser
vers
(rep
licat
es, d
istr
ibu
ted
pro
cess
ing,
dis
trib
ute
d c
om
mit
s)
• Tr
ansa
ctio
ns
(AC
ID p
rop
erti
es, s
eria
lizab
le in
terl
eavi
ngs
, tra
nsa
ctio
n s
ched
ule
rs)
636
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
636
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Ever
ybo
dy
(bes
ides
co
ord
inat
or)
pro
cess
es
hl
lf
hb
d”
yy
()pp
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
All
serv
er d
etec
ttw
o jo
b-m
essa
ges
☞ e
very
bo
dy
pro
cess
es jo
b
632
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
632
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Co
ord
inat
or
rece
ives
job
mes
sage
hl
lf
hb
d
jg
jg
Serv
er
Serv
er
Serv
er
Serv
er
Serv
erSe
rver
Serv
er
Serv
er
Serv
er
Serv
er
Clie
nt
Co
ord
.
Serv
erServ
er
nt
C
Sen
d Jo
b
628
Dis
trib
ute
d S
yste
ms
© 2
019
Uw
e R
. Zim
mer
, The
Aus
tral
ian
Nat
iona
l Uni
vers
ity
page
628
of 7
57 (c
hapt
er 8
: “D
istr
ibut
ed S
yste
ms”
up
to p
age
640)
Dis
trib
uted
Sys
tem
s
Red
und
ancy
(rep
licat
ed s
erve
rs)
Stag
es o
f eac
h s
erve
r:
Job
mes
sage
rec
eive
d b
y al
l act
ive
serv
ers
Job
pro
cess
ed lo
cally
Job
mes
sage
rec
eive
d lo
cally
Rec
eive
dD
eliv
erab
le
Pro
cess
ed
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