Module 1
Introduction to networking and
Application Layer
MODULE-I
Introduction to networks: Network hardware, Network software, Reference
models.
Application Layer: Principles of Network Applications: Network Application
Architectures, Processes Communicating, Transport Services Available to
Applications, Transport Services Provided by the Internet, Application-Layer
Protocols. The Web and HTTP: Overview of HTTP, Non-persistent and Persistent
Connections, HTTP Message Format, User-Server Interaction: Cookies, Web
Caching, The Conditional GET, File Transfer: FTP Commands & Replies, DNS;
The Internet's Directory Service: Services Provided by DNS, Overview of How
DNS Works, DNS Records and Messages
The
Introduction to Understanding the Building Blocks
Networking
(TSO)
▪ Understanding the fundamentals of networks
Theory ▪ Familiarity with network components
session ▪ Understanding network protocols
outcome ▪ Understanding the concept of The concept OSI model
▪ A system of interconnected computers and other
devices that share resources and communicate
with each other.
What is a
Network?
Local Area Network (LAN):
Connects devices within a limited geographical area (e.g., office, school).
Types of •Wide Area Network (WAN): Connects devices over a
Networks large geographical area (e.g., cities, countries).
•Metropolitan Area Network (MAN): Connects devices within a city or
metropolitan area.
Network
Topology
Network
Components
▪ Network devices or nodes are computing devices that need to be linked in the
network. Some network devices include:
• Computers, mobiles, and other consumer devices: These are end devices
that users directly and frequently access. For example, an email originates from
the mailing application on a laptop or mobile phone.
• Servers: These are application or storage servers where the main computation
and data storage occur. All requests for specific tasks or data come to the
servers.
• Routers: Routing is the process of selecting the network path through which
the data packets traverse. Routers are devices that forward these packets
Network between networks to ultimately reach the destination. They add efficiency to
large networks.
Devices
• Switches: Repeaters are to networks what transformers are to electricity
grids—they are electronic devices that receive network signals and clean or
strengthen them. Hubs are repeaters with multiple ports in them. They pass on
the data to whichever ports are available. Bridges are smarter hubs that only
pass the data to the destination port. A switch is a multi-port bridge. Multiple
data cables can be plugged into switches to enable communication with
multiple network devices.
• Gateways: Gateways are hardware devices that act as ‘gates’ between two
distinct networks. They can be firewalls, routers, or servers.
▪ Links are the transmission media which can be of two types:
▪ Wired: Examples of wired technologies used in
networks include coaxial cables, phone lines, twisted-pair
cabling, and optical fibers. Optical fibers carry pulses of
light to represent data.
▪ Wireless: Network connections can also be established
Links through radio or other electromagnetic signals. This kind of
transmission is called ‘wireless’.
▪ The most common examples of wireless links include
communication satellites, cellular networks, and radio and
technology spread spectrums. Wireless LANs use spectrum
technology to establish connections within a small area.
▪ A communication protocol is a set of rules followed by all
nodes involved in the information transfer. Some common
protocols include the internet protocol suite (TCP/IP), IEEE
802, Ethernet, wireless LAN, and cellular standards. TCP/IP is a
conceptual model that standardizes communication in a
modern network. It suggests four functional layers of these
communication links:
▪ Network access layer: This layer defines how the data is
Communicatio physically transferred. It includes how hardware sends data
bits through physical wires or fibers.
n protocols ▪ Internet layer: This layer is responsible for packaging the data
into understandable packets and allowing it to be sent and
received.
▪ Transport layer: This layer enables devices to maintain a
conversation by ensuring the connection is valid and stable.
▪ Application layer: This layer defines how high-level
applications can access the network to initiate data transfer.
Most of the modern internet structure is based on the TCP/IP model,
though there are still strong influences of the similar but
seven-layered open systems interconnection (OSI) model.
IEEE802 is a family of IEEE standards that deals with local area
networks (LAN) and metropolitan area networks (MAN). Wireless LAN
is the most well-known member of the IEEE 802 family and is more
widely known as WLAN or Wi-Fis.
▪ While nodes, links, and protocols form the foundation of
a network, a modern network cannot exist without its
defenses. Security is critical when unprecedented
amounts of data are generated, moved, and processed
across networks.
Network
▪ A few examples of network defense tools include
Défense
firewall, intrusion detection systems (IDS), intrusion
prevention systems (IPS), network access control (NAC),
content filters, proxy servers, anti-DDoS devices, and
load balancers.
▪ Network Interface Card (NIC): A hardware component
that enables a device to connect to a network.
Network
Hardware ▪ Cables
Unshielded Twisted Pair (UTP)
Shielded Twisted Pair (STP)
Coaxial cable Fiber optic cable
Wireless
Networking
▪ Operating Systems
▪ Network functionality: File sharing
Network ▪ Printing
Software ▪ Remote access
▪ Examples: Windows, macOS, Linux
•Definition: Rules that govern communication
between devices on a network.
•Examples:
•TCP/IP
Network
•HTTP
Protocols
•FTP
•SMTP
▪ Networks are organized as a stack of layers or levels,
each one built upon the other.
▪ The number of layers, the name of each layer, the
Protocol contents of each layer, and the function of each layer
Hierarchies differ from network to network.
▪ The purpose of each layer is to offer certain services to
the higher layers
The entities comprising the corresponding layers on different machines are called peers.
The peers may be processes, hardware devices, or even human beings.
No data are directly transferred from layer n on one machine to layer n on another machine. Each
layer passes data and control information to the layer immediately below it, until the lowest layer is
reached.
Below layer 1 is the physical medium through which actual communication occurs.
A set of layers and protocols is called a network architecture. A list of protocols used by a certain
system, one protocol per layer, is called a protocol stack
A five-layer
network
▪ Layers offer two different types of service to the layers above
them: connection-oriented and connectionless.
▪ Connection-oriented service first establishes a connection,
uses the connection, and then releases the connection. eg.
Telephone system.
Connection-Ori ▪ Connectionless service is modelled after the postal system.
ented and Each message carries the full destination address, and each
Connectionless one is routed through the system independent of all the
others.
Services
▪ Unreliable connectionless service is called datagram service,
which does not return an acknowledgement to the sender.
▪ In this service the sender transmits a single datagram
containing a request; the reply contains the answer.
The OSI (Open
Systems
Interconnection
)
▪ Data flows through the OSI model in a step-by-step process:
▪ Application Layer: Applications create the data.
▪ Presentation Layer: Data is formatted and encrypted.
▪ Session Layer: Connections are established and managed.
▪ Transport Layer: Data is broken into segments for reliable
Data Flow In delivery.
▪ Network Layer : Segments are packaged into packets and
OSI Model routed.
▪ Data Link Layer: Packets are framed and sent to the next
device.
▪ Physical Layer: Frames are converted into bits and
transmitted physically
Let’s look at it with an Example:
Luffy sends an e-mail to his friend Zoro.
Step 1: Luffy interacts with e-mail application like
Gmail , outlook , etc. Writes his email to send. (This
happens in Layer 7: Application layer )
Step 2: Mail application prepares for data
transmission like encrypting data and formatting it
for transmission. (This happens in Layer 6:
Presentation Layer )
Step 3: There is a connection established between
the sender and receiver on the internet. (This
happens in Layer 5: Session Layer )
Step 4: Email data is broken into smaller segments. It
adds sequence number and error-checking
information to maintain the reliability of the
information. (This happens in Layer 4: Transport
Layer )
Step 5: Addressing of packets is done in order to find
the best route for transfer. (This happens in Layer 3:
Network Layer )
Step 6: Data packets are encapsulated into frames,
then MAC address is added for local devices and
then it checks for error using error detection. (This
happens in Layer 2: Data Link Layer )
Step 7: Lastly Frames are transmitted in the form of
electrical/ optical signals over a physical network
medium like ethernet cable or WiFi.
After the email reaches the receiver i.e. Zoro, the
process will reverse and decrypt the e-mail content.
At last, the email will be shown on Zoro’s email client
