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Introduction to Data Communication

Data Communication Principles

Overview of Digital Communication

Computer Communication Architecture

Data Link Layer

Medium Access MAC Sub-Layer

Packet Switching

Routing Algorithms

The Network Layer in the Internet

Transport Layer

Application Layer

Other Technologies Overview

Data Communication Model and Types of Network

Introduction to data communication
Exchange of information between two digital devices is data communication or simply data communications refer to the broadcast of this digital data between two or more computers and a computer network or data network that allows computers to exchange data.The actual generation of the information is not part of Data Communications nor is the resultant action of the information at the receiver. Data Communication is interested in the transmission of data, the method of transmission and the preservation of the data during the transfer process form by any electromagnetic system. Data communication is defined as a subset of telecommunication including the transmission of data to and from computers and components of computer systems. More precisely data communication is transmitted via mediums such as wires, coaxial cables, fiber optics, or emitted electromagnetic waves such as broadcast radio, infrared light, microwaves, and satellites.There are so various types of computer networks in existence, it can be hard to understand the differences between them, mainly the ones with very similar-sounding names. This lesson explains the structures and functions of some of the most popular computer networks
Communication model
The architectural model developed by the International Standards Organization (ISO) is often used to explain the structure and purpose of data communications protocols. This ISO model, called theOpen Systems Interconnect (OSI) Reference Model, gives a common reference for discussing communications. The relations defined by this model are clearly stated and widely used in the data communications community—so broadly used, in fact, that it is hard to explain data communications without using OSI’s terminology.
The OSI Reference Model consist of seven layers that explains the functions of data communications protocols. Each layer of the OSI model characterizes a meaning performed when data is shared between cooperating applications diagonally an intervening network. The figure below identifies each layer by name and provides a short useful description for it. Looking at this figure, the protocols are like a stack of building blocks stacked one upon another. Because of this presence, the structure is often called a stack or protocol stack.
A layer does not define a single protocol—it defines a data communications function that may be achieved by any number of protocols. So, each layer may contain several protocols, each providing a service appropriate to the function of that layer. For example, a file transfer protocol and an Email protocol both provide user services, and they are part of the Application Layer.
Application Layer
It is the level of the protocol order where user-retrieved network processes reside. In this framework, a TCP/IP application is any network procedure that occurs above the Transport Layer. This includes all of the procedures that users directly relate with, as well as other procedures at this level that users are not certainly aware of.
Presentation Layer
For collaborating applications to interchange data, they must approve about how data is represented. In OSI, this layer delivers standard data presentation routines. This function is often handled by the applications in TCP/IP, though progressively TCP/IP protocols like XDR and MIME perform this function.
Session Layer
Similar with the Presentation Layer, the Session Layer is not recognizable as a separate layer in the TCP/IP protocol order. The OSI Session Layer arrange the sessions (connection) between cooperating applications. In TCP/IP, this function mainly occurs in the Transport Layer, and the term session is not used. For TCP/IP, the terms socket and port are used to define the path over which uniting applications communicate.
Transport Layer
Most of our discussion of TCP/IP is focused on the protocols that arise in the Transport Layer. The Transport Layer in the OSI reference model assurances that the receiver gets the data same as it was sent. In TCP/IP, this function is achieved by the Transmission Control Protocol (TCP). Not all applications require consistent delivery service. TCP/IP offers a second Transport Layer service, User Data gram Protocol (UDP) that does not perform the end-to-end consistency checks.
Network Layer
The Network Layer manages connections diagonally the network and separates the upper layer protocols from the specifics of the underlying network. The Internet Protocol (IP), which separates the upper layers from the basic network and handles the addressing and distribution of data, is typically defined as TCP/IP’s Network Layer.
Data Link Layer
The consistent delivery of data diagonally the underlying physical network is handled by the Data Link Layer. TCP/IP hardly creates protocols in the Data Link Layer. Most RFCs that relay to the Data Link Layer argue how IP can make use of present data link protocols.
Physical Layer
The Physical Layer describes the characteristics of the hardware desired to transmit the data transmission signal. Features like voltage levels and the number and location of boundary pins are defined in this layer. TCP/IP does not describe physical standards it makes usage of existing standards.
The terminology of the OSI reference model helps us define TCP/IP, but to understand fully, we must use an architectural model that more closely ties the structure of TCP/IP. The next section introduces the protocol model we’ll use to describe TCP/IP.

Types of Network
There are different types of computer networks. Computer networks can be characterized by their scope as well as their purpose.The size of a network can be presented by the geographic area they occupy and the number of computers that are part of the network. Networks can cover anything from a minority of devices within a single room to millions of devices spread across the globe.
Some of the different networks based on scope are

  • Local area network, or LAN
  • Metropolitan area network, or MAN
  • Wide area network, or WAN

In terms of determination, many networks can be measured general purpose, which means they are used for everything from sending files to a printer to retrieving the Internet. Some types of networks, though, serve a very particular purpose. Some of the different networks based on their main purpose are:

  • Storage area network, or SAN
  • Enterprise private network, or EPN
  • Virtual private network, or VPN

Local Area Network (LAN)
A local area network (LAN) is a group of computers and related devices that share a common communications line or wireless link to a server. Normally, a LAN encompasses computers and peripherals associated with a server within a small geographic area such as an office building or home. Computers and other mobile devices can share resources such as a printer or network storage.
A local area network may assist as few users for example, in a home network or as many other hundreds of users. Ethernet and Wi-Fi are the two main commonly used LAN Networks. Other LAN technologies, containing the token ring ,fiber distribute data interface and ARPANET have misplaced favor as Ethernet and Wi-Fi speeds have amplified. The rise of virtualization has powered the development of virtual LANs(VLANs) which permits network administrators to rational group network nodes and screen their networks without the need for main infrastructure changes.Normally, a set of application programs can be reserved on the LAN server. Users who need an application regularly can download it once and then route it from their local device. Users can order printing and extra services as needed through applications run on the LAN server. 
In few conditions, a wireless LAN, or Wi-Fi, may be better to a wired LAN because of its flexibility and cost. Companies are evaluating WLANs as a replacement for their wired infrastructures as various smartphones, tablets, and other mobile devices proliferates.In LAN, we are concerned about "connectivity", linking computers together to share resources. Although the computers consist of several disk operating systems, languages,cabling, and locations, they can communicate to each another and assign resources. The purpose of Data Communications is to deliver the rules and regulations that allow computers with altered disk operating systems, languages, cabling and locations to share resources. The rules and regulations are called protocols and standards in Communications system.
Metropolitan area network (MAN)
A metropolitan area network(MAN) is a network that geographic area or region greater than that covered by even a large local area the area enclosed by a wide area network (WAN). The term is functional to the interconnection of networks in a city into a single greater network (which may then also suggest efficient linking to a wide area network). It is also used to mean the interconnection of numerous local area networks by connecting them with backbone lines. The latter usage is also sometimes denoted as a campus network.Examples. A Metropolitan Area Network (MAN) is a huge computer network on the large geographical area that contains several buildings or even the entire city (metropolis). The geographical area of the MAN is superior to LAN but smaller than WAN.
Wide Area Network WAN)
It is similar to a Local Area Network (LAN), but it's much more bigger. Unlike LANs, WANs are not partial to a single location. Several wide area networks extend long distances via telephone lines, fiber optic cables, or satellite links. They can also be collected of smaller LANs that are organized. The Internet could be explained as the biggest WAN in the world. It can also be called the Internet a Super WAN BAM.
The world's most standard WAN is the Internet. Some parts of the Internet, like VPN-based extra net, are also WANs in themselves. Lastly, many WANs are corporate or research networks that utilize leased lines. WANs generally utilize differently and much more expensive networking equipment than do LANs. Key technologies often found in WANs include SONNET, Frame Relay, and ATM 

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