CS 4504 Lecture Notes - Lecture 3: Presentation Layer, Uniform Resource Identifier, Uniform Resource Locator

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Distributed Computing Chapter 1
Dr. Bobbie
August 22, 2016
Host and resource Identification and Internet Protocol Addresses.
IPv4 scheme is identified with 32-bit string. This means that there can be 232 (4 billion) different
Each IP address must identify both the network on which a host resides and then the particular
host on that network.
The IPv4 working schematic:
Address space is divided into five classes A, B, C, D, E.
oEach class has a unique prefix.
Class a starts with a bit 0
Class B starts with a bit sequence 10
Class C with 110
oThe remaining bits in each address are used for identifying the network and the host.
We need to have different classes in order to accommodate more computers on each network.
Dotted-decimal notation:
32-bit binary expansion
Since the leading bit sequence is 10. This is class B address.
Naming schemes for network resources:
The Domain Name System (DNS)
The extensible Name System (XNS)
Protocol Port numbers
Uniform Resource Identifier (URI) and Uniform Resource Locator (ULR)
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Email addresses
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Identifying Processes with Protocol Ports
In order to deliver data to a specific process we need a scheme. We will discuss Process identifier (PID)
assigned to a process by the operating system. Transportation requires a logical entity known as port.
Note: transport layer in Internet architecture is responsible for dispatching data to processes and two
protocols are used in this layer: TCP and UDP. Each protocol needs its own ports in order to send data on
the machine.
Software Engineering Basics
Procedural languages (C) – uses procedures to break down the complexity of the tasks of an application.
Object-oriented languages (Java) – uses objects to encapsulate the details. Each object simulates an
object in real life.
The Architecture of Distributed Applications
Application (Business) Logic
Using this architecture, the functionalities of a distributed applications can be classified in three layers:
The Presentation layer provides the user interface.
The application logic layer provides the computation for the application.
The service layer provides the underlying services needed to support the functionalities of the
top two layers.
Toolkit/Framework is a collection of classes, tools, and programming samples.
Component-Based software development:
Using this approach, we try to assemble the code using different code fragments. Reusing past
code is essential part of component-based software. This method is used for enterprises to reduce cost
and bugs count.
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