Osi model

ASSIGNMENT # 2
TITLE PAGE
Name: Haider Abbas
Reg.No 2018-kiu-5495
Department : computer science : group : IT
Semester : 4th
THE OSI MODEL
The OSI Model (Open Systems Interconnection Model) is a conceptual framework used
to describe the functions of a networking system. The OSI model characterizes
computing functions into a universal set of rules and requirements in order to support
interoperability between different products and software. In the OSI reference model,
the communications between a computing systems are split into seven different
abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and
Application.
Created at a time when network computing was in its infancy, the OSI was published in
1984 by the International Organization for Standardization (ISO). Though it does not
always map directly to specific systems, the OSI Model is still used today as a means to
describe Network Architecture.
The Seven Layers of the OSI Model
1. Physical Layer
The lowest layer of the OSI Model is concerned with electrically or optically transmitting
raw unstructured data bits across the network from the physical layer of the sending
device to the physical layer of the receiving device. It can include specifications such as
voltages, pin layout, cabling, and radio frequencies. At the physical layer, one might find
“physical” resources such as network hubs, cabling, repeaters, network adapters or
modems.
Role of Layer
Defines the characteristics of the network hardware
Protocols in Physical Layer:
Ethernet, Bluetooth, USB, IEEE802.11 are the various protocol used for this layer.
Devicesused in Layer
Bits. Cables, Radio, Microwave, etc.
2. Data Link Layer
At the data link layer, directly connected nodes are used to perform node-to-node data
transfer where data is packaged into frames. The data link layer also corrects errors that
may have occurred at the physical layer.
The data link layer encompasses two sub-layers of its own. The first, media access
control (MAC), provides flow control and multiplexing for device transmissions over a
network. The second, the logical link control (LLC), provides flow and error control over
the physical medium as well as identifies line protocols.
Role of Layer
Handles the transfer of data across the network media.
Protocols in Data-Link Layer:
PPP, Ethernet are some protocols used by this layer.
Devicesused in Layer
Frames. Ethernet, Wi-Fi AP’s
3. Network Layer
The network layer is responsible for receiving frames from the data link layer, and
delivering them to their intended destinations among based on the addresses contained
inside the frame. The network layer finds the destination by using logical addresses,
such as IP (internet protocol). At this layer, routers are a crucial component used to
quite literally route information where it needs to go between networks.
Role of Layer
Manages data addressing and delivery between networks.
Protocol in Network Layer
The protocol used by this layer are ICMP, IP, ARP, DHCP etc.
Devicesused in Layer
Packets. Routers
4. Transport Layer
The transport layer manages the delivery and error checking of data packets. It
regulates the size, sequencing, and ultimately the transfer of data between systems and
hosts. One of the most common examples of the transport layer is TCP or the
Transmission Control Protocol.
Role of Layer
Manages the transfer of data. Also assures that the received data are identical to the
transmitted data.
Protocols in Transport layer:
Protocols used here are TCP and UDP, STCP etc.
Devicesused in Layer
Segments. Load Balancers/Firewalls.
5. Session Layer
The session layer controls the conversations between different computers. A session or
connection between machines is set up, managed, and terminal at layer 5. Session
layer services also include authentication and reconnections.
Role of Layer
Manages the connections and terminations between cooperating computers.
Protocol in Session layer
The protocol used here is PPTP.
Devicesused in Layer
Data. Load Balancers/Firewalls/Computers
6. Presentation Layer
The presentation layer formats or translates data for the application layer based on the
syntax or semantics that the application accepts. Because of this, it at times also called
the syntax layer. This layer can also handle the encryption and decryption required by
the application layer.
Role of Layer
Ensures that information is delivered to the receiving machine in a form that the
machine can understand.
Protocols in Presentation Layer
The protocol used here is SSL, TLS.
Devicesused in Layer
Data. Load Balancers/Firewalls/Computers
7. Application Layer
At this layer, both the end user and the application layer interact directly with the
software application. This layer sees network services provided to end-user applications
such as a web browser or Office 365. The application layer identifies communication
partners, resource availability, and synchronizes communication.
Role of Layer
Consists of standard communication services and applications that everyone can use.
Protocols in Application Layer:
Protocol user is SMTP, DNS, and HTTP.
Devices used in Layer
Data. Load Balancers/Firewalls/Computers
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