Network Fundamentals - Communicating over the Network

What is a network?

•   Data or information networks capable of carrying many different types of communications

three common elements of communication

•   message source
•   channel/media
•   message destination

For example, PC1 want to send a message "hello" to PC2. 
Message source : PC1
Media : network cable, wireless media
Message destination : PC2

How messages are communicated

Data is sent across a network in small “chunks” called segments

Segmentation: Breaking communication into pieces
Multiplexing: Interleaving the pieces as they transverse the media

You can think it like your mouth. When you eat food, you must use your tooth to make the food small piece, this like segmentation. And your can eat ice-cream and apple in the same time, this like multiplexing

 

 

 

 

Network components

Hardware

•   device, media

Software/service

Basic Network Components

Network devices / Intermediary  devices
provide connectivity and ensure data flows in the network
e.g. Router, Switch, Hub, Wireless device, etc.

End devices
provide services directly to end users
is the interface between human and network
e.g. PC, server, networked printers, etc.

Network media (medium)

Network cable, wireless media

Role of end devices

Act as client or server or both

Basic Network Components

Network media

•   Channel over which a message travels

Factors to choose the media:

•   Speed
•   Cost
•   Mobility
•   Distance
•   Environment
•   Data Amount

 

 

Software/Services

Services and processes are the communication programs, called software, that run on the networked devices.
A network service provides information in response to a request.

Network Types

Local Area Networks (LANs)

•   A network serving a home, building or campus is considered a Local Area Network (LAN)

Wide Area Networks (WANs)

•   LANs separated by geographic distance are connected by a network known as a Wide Area network (WAN)

Internet is defined as  a global mesh of interconnected networks

Network Symbols

Protocols

• The importance of protocols and how they are used to facilitate communication over data networks

                 A protocol is a set of predetermined rules to govern communications

• Network protocols are used to allow devices to communicate successfully

 

Technology independent Protocols

Different types of network devices can communicate using the same sets of protocols.

This is because protocols specify network functionality, not the technology of devices

Protocols in Network Communication

• Protocol suites and industry standards

       A protocol suite is

       A group of inter-related protocols that are necessary to perform a communication function.
       They are implemented in software and hardware that is loaded on each host and network device.
       For example: TCP/IP suite

       A standard is

       A process or protocol that has been endorsed by the networking industry

       and ratified  by a  standards organization.

       For example:The Institute of Electrical and Electronics Engineers (IEEE),

                            Internet Engineering Task Force (IETF)

Example of protocol suites

The interaction between a Web server and a Web browser as an example to explain the protocol suites

Layered Network Model

Benefits of using a layered model

 include:

•   assists in protocol design
•   fosters competition
•   changes in one layer do not affect other layers
•   provides a common language

Networking Models

Two basic types of networking models:

• Protocol model

            It provides a model that closely matches the structure of a particular protocol suite.

            For example:

                  TCP/IP model is a protocol model because it describes the functions that occur   at each layer of protocols within the TCP/IP suite.

• Reference model

          It provides a common reference for maintaining consistency within all types of network protocols and services. Its primary purpose is to aid in clearer understanding of the functions and process involved.

          For example: Open Systems Interconnection (OSI) model

TCP/IP Model

• Created in the early 1970s and is referred to as the Internet model
• Open Standard 

Communication Process

Protocol Data Unit

Protocol data units (PDU) and encapsulation

Process of sending and receiving messages

OSI Model

• It provides a framework on which to build a suite of open systems protocols.

• Unfortunately, the speed at which the TCP/IP based Internet was adopted, and the rate at which it expanded, caused the OSI Protocol Suite development and acceptance to lag behind.

  

Layers with TCP/IP and OSI Model

Compare OSI and TCP/IP model

Addressing and Naming Schemes

• Encapsulation headers are used to manage communication in data networks

• Using the OSI model as a guide, we can see the different addresses and identifiers that are necessary at each layer

• Destination and source physical addresses is concerned with the delivery of messages on a single local network.  

• For example: In an Ethernet LAN, this address is called the Media Access Control (MAC) address.

• Destination and source logical network addresses are used to manage communication in different data networks. 
• For example: IP address

• Destination and Source port numbers are used to identify the source and destination processes for data communication.