KEY TERMS in Computer Networks

Following are some important terms, which are frequently used in context of Computer Networks.

Terms	Definition
1. ISO	The OSI model is a product of the Open Systems Interconnection project at the International Organization for Standardization. ISO is a voluntary organization.
2. OSI Model	Open System Interconnection is a model consisting of seven logical layers.
3. TCP/IP Model	Transmission Control Protocol and Internet Protocol Model is based on four layer model which is based on Protocols.
4. UTP	Unshielded Twisted Pair cable is a Wired/Guided media which consists of two conductors usually copper, each with its own colour plastic insulator
5. STP	Shielded Twisted Pair cable is a Wired/Guided media has a metal foil or braided-mesh covering which encases each pair of insulated conductors. Shielding also eliminates crosstalk
6. PPP	Point-to-Point connection is a protocol which is used as a communication link between two devices.
7. LAN	Local Area Network is designed for small areas such as an office, group of building or a factory.
8. WAN	Wide Area Network is used for the network that covers large distance such as cover states of a country
9. MAN	Metropolitan Area Network uses the similar technology as LAN. It is designed to extend over the entire city.
10. Crosstalk	Undesired effect of one circuit on another circuit. It can occur when one line picks up some signals travelling down another line. Example: telephone conversation when one can hear background conversations. It can be eliminated by shielding each pair of twisted pair cable.
11. PSTN	Public Switched Telephone Network consists of telephone lines, cellular networks, satellites for communication, fiber optic cables etc. It is the combination of world’s (national, local and regional) circuit switched telephone network.
12. File Transfer, Access and Management (FTAM)	Standard mechanism to access files and manages it. Users can access files in a remote computer and manage it.
13. Analog Transmission	The signal is continuously variable in amplitude and frequency. Power requirement is high when compared with Digital Transmission.
14. Digital Transmission	It is a sequence of voltage pulses. It is basically a series of discrete pulses. Security is better than Analog Transmission.

Comparison of OSI Reference Model and TCP/IP Reference Model

Following are some major differences between OSI Reference Model and TCP/IP Reference Model, with diagrammatic comparison below.

OSI(Open System Interconnection)	TCP/IP(Transmission Control Protocol / Internet Protocol)
1. OSI is a generic, protocol independent standard, acting as a communication gateway between the network and end user.	1. TCP/IP model is based on standard protocols around which the Internet has developed. It is a communication protocol, which allows connection of hosts over a network.
2. In OSI model the transport layer guarantees the delivery of packets.	2. In TCP/IP model the transport layer does not guarantees delivery of packets. Still the TCP/IP model is more reliable.
3. Follows vertical approach.	3. Follows horizontal approach.
4. OSI model has a separate Presentation layer and Session layer.	4. TCP/IP does not have a separate Presentation layer or Session layer.
5. OSI is a reference model around which the networks are built. Generally it is used as a guidance tool.	5. TCP/IP model is, in a way implementation of the OSI model.
6. Network layer of OSI model provides both connection oriented and connectionless service.	6. The Network layer in TCP/IP model provides connectionless service.
7. OSI model has a problem of fitting the protocols into the model.	7. TCP/IP model does not fit any protocol
8. Protocols are hidden in OSI model and are easily replaced as the technology changes.	8. In TCP/IP replacing protocol is not easy.
9. OSI model defines services, interfaces and protocols very clearly and makes clear distinction between them. It is protocol independent.	9. In TCP/IP, services, interfaces and protocols are not clearly separated. It is also protocol dependent.
10. It has 7 layers	10. It has 4 layers

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Diagrammatic Comparison between OSI Reference Model and TCP/IP Reference Model