Transcript Computer Signals

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.
Understand Network
Communication
 Computer signals
 Messages
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.
File Transfer Protocol (FTP)
 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.
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.
Simple Mail Transfer Protocol
(SMTP)
 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.
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.