In the late 1970s, two projects began independently, with the same goal: to define a unifying standard for the architecture of networking systems. One was administered by the International Organization for Standardization (ISO), while the other was undertaken by the International Telegraph and Telephone Consultative Committee (CCITT). These two international standards bodies each developed a document that defined similar networking models. In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection. The concept of a seven-layer model was provided by the work of Charles Bachman at Honeywell Information Services The ISO-OSI model consists of seven layer architecture. It defines seven layers or levels in a complete communication system
Layer 1 : Physical
Layer 2 : Data Link
Layer 3 : Network
Layer 4 : Transport
Layer 5 : Session
Layer 6 : Presentation
Layer 7 : Application
Layer 1: The Physical Layer The bottom most layer of the OSI model is the physical layer. It addresses the physical characteristics of the network i.e., it activates, maintain and deactivate the physical connection. Voltages and data rates needed for transmission. In this layer data will be in the form of electronic signals called bit stream (0 and 1). Devices used in this layer are Repeater and Hub.
Layer 2: Data Link Layer Data Link Layer is the second layer in the OSI model. In data link layer data is transformed in the form of frames. In this layer devices like Switch and Bridge are used. IEEE 802 divides the data link layer into two sub layers:
1) Media Access Control (MAC) layer: It contains the address of each device on a network which is assigned to the device during its manufacturing.
2) Logical Link Control (LLC) layer: In this layer the redundant data and error data can be detected using cyclic redundancy check
Layer 3: The Network Layer This layer provides the functional & procedural means of transferring variable length data sequences (called datagram’s) from one node to another connected to the same network. In this layer router is used to connect devices of different networks. It routes the signal through different channels to the other end. It acts as a network controller. It decides by which route data should take. It divides the outgoing messages into packets and to assemble incoming packets into messages for higher levels.
Layer 4: Transport Layer The main purpose of transport layer is to ensure that packets are moved over the network without errors and data loss. It decides if data transmission should be on parallel path or single path. Functions such as multiplexing, segmenting or splitting on the data done by layer four that is transport layer. Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
Layer 5: The Session Layer Session layer manages and synchronize the conversation between two different applications. Transfer of data from one destination to another session layer streams of data are marked and are resynchronized properly, so that the ends of the messages are not cut prematurely and data loss is avoided. In session layer during large file transfers it maintains check points.
Layer 6: The presentation Layer Presentation layer takes concern that the data is sent in such a way that the receiver will recognize the information (data) and will be able to use the data. Data encryption, decryption, compression and decompression is done in the presentation layer
Layer 7: Application Layer It is the top layer. Manipulation of data (information) in various ways is done in this layer. Transferring of files disturbing the results to the user is also done in this layer. Mail services, directory services, network resource etc are services provided by application layer.
1. In which layer data will be in the form of bit stream
a) Physical layer
b) Data link layer
c) Application layer
d) Network layer
e) Session layer
2. Data encryption and decryption is done in which layer
a) Network layer
b) Physical layer
c) Transport layer
d) Presentation layer
e) None of these
3. OSI Stands for
a) Open Source Interconnect
b) Open System Interconnect
c) Open Systems Interconnection
d) Open Sources Interconnected
e) None of these
4. ISO stands for
a) International Standardization Organization
b) International Standard Organization
c) International Standard for Organization
d) International Organization for Standardization
e) None of These
5. MAC layer is a sub layer of _______layer
a) Physical layer
b) Data link layer
c) Application layer
d) Network layer
e) Session layer
6. Repeater is used in which layer
a) Network layer
b) Physical layer
c) Transport layer
d) Presentation layer
e) None of these
7. Router is used in which layer
a) Physical layer
b) Data link layer
c) Application layer
d) Network layer
e) None of these
8. Cyclic Redundancy Check is
done in which layer
a) Network layer
b) Physical layer
c) Transport layer
d) Presentation layer
e) LLC Layer
9. Check points are maintained ___ layer
a) Physical layer
b) Data link layer
c) Application layer
d) Network layer
e) Session layer
10. IPX stands for __________
a) Internet Packet Exchange
b) Internet Protocol Exchange
c) Internetwork Packet Exchange
d) Intranet Protocol Exchange
e) None of these
11. Which protocol is considered as connectionless protocol?
a) SMTP
b) FTP
c) TCP
d) UDP
e) IP
12. IP protocol is used in which layer
a) Physical layer
b) Data link layer
c) Application layer
d) Network layer
e) None of these
13. Bridge is used in which layer
a) Session layer
b) Physical layer
c) Application layer
d) Network layer
e) Data link layer
14. The concept of OSI seven layers was proposed by_________
a) Charles Babbage
b) Von Neumann
c) Lovelace
d) Hopper
e) Charles Bachman
15. LLC stands for
a) Logic Layer Control
b) Logical Control Layer
c) Logic Link Control Layer
d) Logic Links Centre Layer
e) None of These
16. The Internet began with the development of
a) USENET
b) ARPANET
c) Ethernet
d) Intranet
e) None of these
17. A global network made up of thousands of privately owned computers and networks is called the:
a) World Wide Web
b) Internet
c) Specialized search engine
d) Internet2
e) None of these
18. A peer-to-peer LAN is an appropriate network architecture for__
a) The Internet
b) Home network
c) Network requiring a server with shared resources
d) wide area network
e) None of these
19. What is a serial port that adds a direct connection to a network?
a) FireWire
b) NIC
c) USB
d) Server
e) None of these
20. The_________ runs the front end applications software in a network.
a) Client
b) Database
c) Server
d) USB
e) None of these
21. This device is used to connect your computer with a telephone line, so that can access information from other servers and ordinary users too, said device is called ___________
a) Modem
b) Set Top Box
c) LAN Card
d) UPS
e) None of these
22. Device on one network can communicate with devices on another network via_______
a) File Server
b) Utility Server
c) Printer Server
d) Gateway
e) None of these
23. Which of the following will connect you to the Internet?
a) An commercial online service
b) An internet service provider
c) A network connection
d) All of the above
e) None of these
24. The word FTP stands for______
a) File Translate Protocol
b) File Transits Protocol
c) File Typing Protocol
d) File Transfer Protocol
e) None of these
25. _____ is a set of rules computers utilize to talk to each other.
a) Protocol
b) Syntax
c) DOS command
d) HTML
e) None of these
26. Which type of transmission media is acknowledged as regular telephone wire?
a) Wi-Fi
b) Twisted-pair wire
c) Fiber optic cable
d) Coaxial cable
e) None of these
27. What is the idea of a firewall on a computer?
a) To protect a computer from unauthorized access
b) To protect a computer in case of fire
c) To protect a computer from spam
d) All of the above
e) None of these
