Consensus and agreement algorithms Some notes on Distributed Systems Written while studying the course Distributed Systems at IIIT Hyderabad, by professor Kishore Kothapalli. The book used is Distributed Computing: Principles, Algorithms, and Systems by Ajay D. Kshemkalyani and Mukesh Singhal.

1. cONSENGUs AND AGRELMINT ALGHORITHMS
A)8MCuRoNes chMO NI ATION
a veo m r in the
ECEman)
euna.
Cdnaute data wele pr riet und.)
pagate aNe nts) dugnguisihet bren reciep ob *
re nidtngc
NETNOAK ceNNLCTivITY SENDER IDENTIFICATIoN
PYM u t crntcttd Cegca) Gnder o a ms atuag noa
CHANNLL REURBL UWAu TMENTI CmeD
MESsn GtS
channels a ltabie, ent pretcses
ad. woress
may tomper a
m
Calao cnled bvat mág)
AGREEMENT VARIABLE
c be u dme vEat4).
LSNgENDUS FROBLEMAGREEMENT PRobLEM
acprecs Fas al value,at all
allnonbu p t agTce abeut ininal
wutt a T on ona valve
valee
u r a Procaa4.
nafon
rttment: Valu termination
vaVd m tnitial valuE a ade
d vsivd art aame
al.d
ama
n Prec a deoide

2. renan e t u n t
Ah rece b
* m a l vefue
o vtr proceLs nd arriv d on
*** n ma, najont
h c
decik on tueutd
* t
n rnt jer
P e d a s inee tiwe are no t u a
FAIL STOP CoNSEN&US
a gonithm hai
6*
round. a* S** ech
,
d p r e t dndi
vorinble +o
Fo acm=
a other prscee drt o aund
* aunds, ar ent raune h a no
ade
a e ena
d6 *a reund cern@nge
rEachad. 6urë rond do rot ac e ongengus. m mpler OC Cgen)n*)
Y2ANTINE R oNEENES
engtnus on b achitved (5°').
deure4 Pread **reuna
" )

3. *
j*ecc4, and *
ch ecei a
r
e N d 4-tncn precete
chtvtd e r h e n a t eeit Corm-nutt) Ca achieue
n
uneng themEelve
tender
eattw
:
P
P

4. aher ynch, paterson
6alorcmodel hchronous tevn s8cronous stom
agreementnone
Vagreement
V conmon knauoledg V encovrent common knbwle
axtstop
-stop V agreement X 0g reemet
bn proLesses
aC6t rounds
byzantine ogreeme x agreemnt
36 D proacsses
ng) raonds
intrdaoducing a leader Coill Solve
al problemS
but what cb the teader beco mes 6aulty?
PAXOS githona egslative consensus stem used on paxes istand on qrecece
althbugh no deterministic outt folerant consensus proto ol an gvarentee Proqress
in an aure netuerk. Cproved 6cher, gneh, and paterton), paros guarentes
Saedy C0onitenw
nd the Conditions at ould prevent t rom maki
Progrags dre dekfieutt to proveke,