Computer Network OSI Model

Computer networking refers to interconnected computing devices (switches, routers, bridges, repeaters, and gateways) that can exchange data and share resources with each other.

First Network

1. ARPANET was created by the US Department of Defense in 1969.
2. The first email message was sent over Arpanet in 1971.
3. Network/Internet: BOB KHAN AND VINT SERF
4. Internet was officially announced in all over the world on 1^st Jan, 1983 by Telnet.
5. The first publically available internet was launched by state owned vides sanchar nigam limited (vsnl) on 15^th Aug 1995.

A networking model is a set of guidelines and standards that define how data is transmitted and received over a network. It is also known as the networking architecture or a networking blueprint.

There are two types of models in Networking Models:

1. TCP/IP MODEL (197-1983): Transmission Control Protocol and Internet Protocol =1970 (adopted as the protocol standard for ARPANET =IN 1983).
2. OSI MODEL (1984) : Open System Interconnection Model =1984

OSI Model

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

Its work on bottom up approach

Notes:

1. Initially First layers i.e. Physical, Data Link and Network Layer are known as hardware layers.
2. Bottom 3 layers layers application, presentation and session layer are known as software’s layers.
3. Heart of the OSI model is transport Layer
4. OSI is developed by International organization for standardization
5. It is a Reference model or conceptual model
6. This model is not practically implemented
7. In OSI model Data Link Layer is divided in two sub layer i.e Logical Link Layer and Media Access layer

OSI Model =PDU (Presentation Data Unit)

1. Physical Layer  = Bits
2. Data Link Layer = Frames
3. Network Layer= Packet’s
4. Transport Layer =Segments
5. Session Layer= Data
6. Presentation Layer= Data
7. Application Layer= Data

OSI Model =Devices Works

1. Physical Layer  = Hub, Repeater , Modem , cables
2. Data Link Layer = Switch, Bridge , Modem,
3. Network Layer= Router
4. Transport Layer =Gateway
5. Session Layer= Gateway
6. Presentation Layer= Gateway
7. Application Layer= Gateway

Note:

• Gateway can work on all 7 layers of OSI Model
• Firewall works on Network and Transport Layer
• Gateway manage two different Network/topology/

OSI Model =Address used

1. Physical Layer  =
2. Data Link Layer = MAC / Physical Address
3. Network Layer= IP/Logical Address
4. Transport Layer = Port Address
5. Session Layer=
6. Presentation Layer=
7. Application Layer=

Note:

• MAC address is always fixed where IP address will changed
• MAC address is mentioned on NIC card on computer. By replacing the NIC card one can change the MAC address
• The Process of hide MAC address and IP Address is called spoofing.

Categories: computer network