Token-Dased DMX
Algorithms
Suzuki-Kasamis broadcast
Raymonds tree
Token-Based Algorithms
A unique token is shared among all sites
A site is allowed to enter a critical section (CS) if
it possesses the token
Token-based algorithms use sequence numbers
inst
Consensus & Agreement
Example
Five independent sensors measure the
temperature T of a furnace. Each sensor
checks if T is greater than 1000C. Some
sensors may be faulty, but it is not known which
are faulty. The nonfaulty sensors have to agree
about the t
Fault Tolerant Systems
Rollback Recovery Protocols
Introduction
Rollback recovery treats a distributed system as a
collection of processes that communicate through a
network
Fault tolerance is achieved by periodically using stable
storage to save the pr
Fault Tolerance
Part I Introduction
Part II Process Resilience
Part III Reliable Communication
Part IV Distributed Commit
Part V Recovery
Fault Tolerance
Part I
Introduction
Fault Tolerance
A DS should be fault-tolerant
Should be able to continue functi
FaultTolerance
Agreement in presence of faults
Byzantine generals problem
Reliable communication
Distributed commit
Two phase commit
Three phase commit
Failure recovery
Checkpointing
Message logging
FailureMaskingbyRedundancy
Triple modular redu
An interconnected collection of
autonomous computers
What do we mean by
autonomous here?
If one computer can forcibly
start, stop, or control another
one, then the computers are not
autonomous.
Users must explicitly log onto one m/c,
explicitly submit jo
Distributed Mutual Exclusion
Distributed Mutual Exclusion
(DME)
Mutual exclusion
ensures
that concurrent processes have serialized
access to shared resources - the critical section
problem.
At any point in time, only one process can be
executing in its
ConsistencyandReplication
DistributedSystems
Major issues:
Transparency
Scalability
Whyreplication?
To enhance reliability
If one replica is unavailable or crashes, use another
Protect against corrupted data
To improve performance
Scale with size of
Election Algorithms
Outline
Election algorithms introduction
Traditional election algorithms
Bully algorithm
Ring algorithm
Wireless election algorithms
Need for a Coordinator
Many algorithms used in distributed
systems require a coordinator
For ex
DistributionProtocols
Replica Placement
Update Propagation
Epidemic Protocols
ReplicaPlacement
Replica server placement
Web: geophically skewed request patterns
Where to place a proxy?
Permanent replicas
Eg Mirroring: all replicas mirror the same
Running head: SECURITY STRATEGIES IN CLOUD COMPUTING
Security Strategies in Cloud Computing
A Research Report for the DSCI Capstone Project In Computer Science Course
Students Name
Institutional Affiliation
Date
1
SECURITY STRATEGIES IN CLOUD COMPUTING
2
