Distributed System Models: Lecture 2a

Question 1

Major Concerns of Architectural Models

Answer 1

1) Performance
2) Reliability
3) Availability
4) Cost-effectiveness

Question 2

Differences between Client-Server and Peer-to-Peer Model

Answer 2

In Client-Server there is distinction between roles while in Peer-to-Peer there is not distinction between roles and have the same functions and responsibilities.

Question 3

Design Requirements for Distributed Architectures

Answer 3

1) Performance Issues
- Responsiveness
- Throughput
- Load balancing; Caching and replication

2) Quality of Service
- Reliability, security and performance

3) Dependability
- Crucial for safety-critical systems; correctness, security, fault tolerance

Question 4

What is Bandwidth?

Answer 4

The bandwidth of a computer network is the total amount of information that can be transmitted over it in a given time.

Question 5

What is Jitter?

Answer 5

Jitter is the variation in the time taken to deliver a series of messages.

Question 6

Three type of failures are considered for each type of component of a model

Answer 6

1) Omission failures
- Process omission failure
- Communication omission failure

2) Arbitrary / Byzantine failures
- Worst possible failure
- Message contents are corrupted
- Non-existent messages are delivered
- Real messages delivered more than once

3) Timing failures
4) Masking failures

Question 7

Threats

Answer 7

1) Validity, Integrity, Privacy
2) Denial of Service
3) Mobile Code
4) Security and Threat Models