Lesson 3-Communicating Over Networks. Overview Understand network communication. Decipher computer...

Lesson 3-Communicating Over Networks

Overview

Understand network communication.

Decipher computer addressing.

Network communication protocols.

Network designing.

Understand Network Communication

A sender, a receiver, a message, and a medium are

required for network communication.

In order to communicate effectively, it is essential that the

systems on a network use the same language.

Computer signals

Messages

Understand Network Communication

Computer Signals

Digital signal and analog signal are the two forms in which

computer signals are transmitted.

When two computers communicate on a network, they

exchange digital signals.

Each signal or digit is represented by a distinct state.

Computer Signals

An analog signal

Computer Signals

The presence of an electrical signal is considered as ‘on,’

and is represented by the digit one.

The absence of an electrical signal is considered as ‘off,’

and is represented by a zero.

A system that uses zeros and ones is called a binary

system.

Computer Signals

A modem is required to convert a digital signal into an

analog signal, and vice versa.

The process of converting digital signals into analog signals

is called modulation.

The process of converting analog signals back into digital

signals is called demodulation.

Computer Signals

Bits:

The term ‘bit’ is used to represent a single instance of a digital

signal.

These can also be represented by other medium states, such

as the relative signal strengths of light pulses or radio waves.

A bit becomes important when it is combined with other bits to

create different characters.

Computer Signals

Bytes:

Eight bits make a byte.

A byte can be used to represent up to 256 characters, digits, or

symbols on a computer.

Messages

When a computer communicates with itself or with other

computers, it assembles the characters into meaningful

data.

The data can then be easily received and interpreted by the

receiving computer.

Decipher Computer Addressing

Unique address.

Physical address.

Hexadecimal notation.

Node address.

Network addresses and their implementation.

Unique Address

A unique address with an exact name and storage path is

required for storing and retrieving data accurately over a

network.

Network addressing is handled by ensuring that each

address is unique.

Physical Address

The physical address is the first element of a computer’s

network address.

It is a special serial number assigned to a component

installed inside the computer.

The numbers are controlled by the networking industry’s

regulating organization, the Institute of Electrical and

Electronics Engineers (IEEE).

Physical Address

The equipment manufacturer requests a block of unique 48-

bit binary numbers and assigns a separate number to each

network interface card (NIC) that they create.

The first 24 bits of the MAC address assigned to a NIC are set

by the IEEE to identify the manufacturer.

The second 24 bits are used for a unique serial number that is

assigned to the individual network interface card by its

manufacturer.

Physical Address

The physical address, also know as the Media Access

Control (MAC) address, is a means by which the computer

gains access to the networking medium.

The physical (or MAC) address is also sometimes referred to

as the hardware address.

Hexadecimal Notation

Hexadecimal notation (hex) is a numbering system that

uses 16 alphanumeric characters instead of the usual ten

numeric digits.

Hex is a shorthand for writing binary numbers.

A single hex digit is used to represent four digits of a binary

number.

Node Address

A unique node address is required for every computer on a

network.

Adding node numbers to the MAC helps locate the

randomly generated node numbers.

Each node address is useful within the specific network to

which it is attached.

Network Addresses and Their Implementation

The network address is a combination of the node address

and the MAC address.

The source address and the destination address are

required to transmit data effectively.

The source address specifies where the transmitted

information originates.

Network Addresses and Their Implementation

The destination address specifies the information’s

destination.

Both the source and destination addresses are then added

to the data being transmitted to make sure that the

message is routed properly.

Network Addresses and Their Implementation

Directing messages to the specific computer

Network Communication Protocols

Network communication decisions.

Layered communication.

Internet communication.

Intranet/Extranet communication.

Network Communication Decisions

Language:

A set of language rules developed to effectively communicate

over a network is called a protocol.

NetBIOS (Network Basic Input/Output System) and NetBEUI

(NetBIOS Extended User Interface) were two networking

languages used earlier.

Network Communication Decisions

Broadcasting versus routing:

Broadcasting involves passing digital messages over the

network medium.

Routing involves deciding the recipient of the message and

sending it to them directly.

Network Communication Decisions

Message format - Formatting refers to combining mutually

acceptable characters in such a way that messages can be

exchanged.

Layered Communication

The International Standards Organization (ISO) suggested

the use of the Open Systems Interconnection (ISO) model to

explain network communication.

The OSI model’s standards are open and made available to

everyone to enable interconnectivity of different systems.

The model simplifies complex networking activities by

grouping the steps into seven layers.

Layered Communication

Layers in the OSI Model

Layered Communication

Layers in the OSI Model

Internet Communication

Transmission Control Protocol/Internet Protocol (TCP/IP).

User Datagram Protocol (UDP).

Domain Name Service (DNS).

File Transfer Protocol (FTP).

Simple Mail Transfer Protocol (SMTP).

Transmission Control Protocol/Internet Protocol (TCP/IP)

TCP/IP is the most widely used protocol, and acts as the

Transport/Network layer protocol.

The TCP makes sure that the data is correctly sized,

properly put in packets, and sequenced back in the right

order upon receipt.

The TCP, also known as a connection-oriented protocol,

links the Application layer to the Network layer.

Transmission Control Protocol/Internet Protocol (TCP/IP)

The IP is a set of rules that is concerned with sending a

message to the correct address and is, therefore, called a

connectionless protocol.

The IP is also responsible for the creation and maintenance

of an addressing scheme, known as the IP address.

IP operates at the Network layer.

Transmission Control Protocol/Internet Protocol (TCP/IP)

Each IP address is a unique 4-byte (or 32-bit) number, and

each byte is separated by a decimal point.

IP addresses can be used as static assignments to

individual computers, or can be assigned dynamically.

Transmission Control Protocol/Internet Protocol (TCP/IP)

The Dynamic Host Configuration Protocol (DHCP) is used to

assign IP addresses dynamically.

The DHCP is a set of rules that allow a group of computers

to effectively lease IP numbers to network members when

required.

User Datagram Protocol (UDP)

UDP is a connectionless protocol that operates at the

Transport layer.

This protocol does not have to open a connection with the

receiver and it does not have to carry out any error

correction.

UDP does not perform any checks to ensure the receipt of

data, so it never carries out automatic retransmissions.

Domain Name Service (DNS)

The DNS is used for locating resources on the Internet.

It operates at the Application layer.

The DNS server uses the IP address to link to the Uniform

Resource Locator (URL) concerned.

Examples of domain names include com, net, org, edu, gov,

and mil.

File Transfer Protocol (FTP)

The FTP is used for transferring files over the Internet.

It operates using a client at the Application layer and a

server at the opposite end.

It is also possible to send files to an FTP site, making the

process of exchanging large pieces of information fast and

simple.

Some FTP servers allow anonymous logins, while others

require passwords and proper authentication.

File Transfer Protocol (FTP)

Simple Mail Transfer Protocol(SMTP)

SMTP is a set of rules that regulates the transfer of e-mail

over the Internet.

The Post Office Protocol (POP) or the Internet Message

Access Protocol (IMAP) is required to read e-mail.

Graphic or document attachments are handled by an SMTP

extension called Multipurpose Internet Mail Extensions

(MIME).

The MIME converts each attachment into a coded form,

similar to text, for transfer over SMTP.

Simple Mail Transfer Protocol(SMTP)

Intranet/Extranet Communication

Intranet communication refers to using Internet

communication techniques without using an Internet

connection.

When two or more Intranets are networked without being

connected to the Internet, it is called an Extranet.

Network Designing

Network needs.

Network choices.

Network layout.

Network Needs

Administering a network involves:

Ensuring that the systems are up and running at any given

point in time, while making them easy for a user to operate.

Maintaining the system’s operation with the minimum amount

of downtime.

Network Choices

Network budget – The total cost of the network must be

less than the projected earnings to impose an economic

limit for installing and maintaining a network.

Network security – The required security must be

essentially added to the network to avoid any kind of

security issues.

Network Choices

The following aspects must be considered while choosing a

network’s users:

The network’s users should be trained and be capable of

handling the system.

The number of users who would be accessing the system

should be defined at a given point in time.

Network Choices

The following aspects must be considered while choosing a

network’s users (continued):

It must be ensured that when the network access is at its

peak, the users are able to obtain the services immediately

after logging in.

The maximum capacity of the network should be designed

to handle a user’s request.

Network Choices

Network application:

It is essential to know how and why the network would be

used.

These facts help determine the means for producing the

network’s output and the tools that go into producing it.

Network Choices

Network growth:

Any system should allow for future growth, and should include

added capacity for incorporating new resources into the

network.

Allowances should also be provided for technological

advances.

Network Layout

The physical layout or the geometric pattern formed by the

arrangement of interconnected computers is referred to as

topology.

Bus, ring, and star are the three most common types of

physical topologies.

Network Layout

Bus topology

Network Layout

Ring topology

Network Layout

Star topology

Summary

Communication involves a sender, a receiver, a message,

and a medium.

A bit is a single digit and a byte is made up of eight bits.

A system that uses only zeros and ones is called a binary

system.

A modem is required to convert digital information into

analog, and vice versa.

Summary

The ISO recommends the use of the OSI model to connect

dissimilar networking components.

The needs of all the networked resources should be

adequately considered while panning the network.

Topology refers to the physical layout or arrangement of

computers in a network.

The three most common topologies are bus, ring, and star.