Question

5. What is a three-tiered client-server architecture? (5marks) 6. In Table 1 below, describe the characteristics of the following multi-threaded server models. (6 marks) Table 1: Multi-threaded Server Models Characteristic Threads Single-threaded processes Finite-state machine

Answer 1

Answer:

Client server architecture:

A three-tier client/server is a type of multi-tier computing architecture in which an entire application is distributed across three different computing layers or tiers. It divides the presentation, application logic and data processing layers across client and server devices.

In 3-tier architecture, there is an intermediary level, meaning that the architecture is generally split up between: a client, i.e. the computer, which requests the resources, equipped with a user interface (usually a web browser) for presentation purposes; the application server (also called middleware), whose task it is to provide the requested resources, but by calling on another server; and the data server, which provides the application server with the data that it requires:

Answer 2:

Thread - A thread is a path of execution within a process. A process can contain multiple threads. A thread is also called a lightweight process. Threads provide a way to improve application performance through parallelism.

Characteristics:

• Threads minimize the context switching time.

·    Use of threads provides concurrency within a process.

• Use of threads provides concurrency within a process.

Single threaded process –

Characteristics :

• Can use only one CPU.
• If you have only 1 cpu, and the tasks have no blocking I/O, then the single threaded will finish equal to or faster than multi-threaded, as there is overhead to switching threads.
• If you have 1 cpu, but the tasks involve a lot of blocking I/O, you might see a speedup by using threading, assuming work can be done when I/O is in progress.

Finite state machine-

A finite state machine is a computation model that can be implemented with hardware or software and can be used to simulate sequential logic and some computer programs. Finite state automata generate regular languages. Finite state machines can be used to model problems in many fields including mathematics, artificial intelligence, games, and linguistics.

Characteristics:

• Inputs: assumed to be sequences of symbols selected from a finite set I of input signals. Namely, set I is the set {x₁, x,₂, x₃... x_k} where k is the number of inputs.
• Outputs: sequences of symbols selected from a finite set Z. Namely, set Z is the set {y₁, y₂, y₃ ... y_m} where m is the number of outputs..
• States: finite set Q, whose definition depends on the type of automaton.