Data Communication & Application Layer

1) Explain how a message is transmitted from one computer to another, using layers of the OSI model

ISO and ANSI discovered the need for standard means in open communications implementation; this leads to the development of the seven-layer network communications model identified as Open Systems Interconnect. The OSI model serves as the common link that permits data to be reliably transmitted and exchanged. Even if it does not really carry out any functions or perform any actual work, the OSI model describes the way things should be done by the software and hardware within a network in order for communications to take place in two computers or nodes.

Through this, the OSI model presents a universal set of rules that enables various manufacturers and developers to produce software and hardware that is attuned with each other. The value of the OSI model with deference to network communications aside from being the foundation for all network communications nowadays, it is also a fundamental part communications, and it becomes very evident that it is very significant for a network technician to have an understanding of the OSI model.

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The OSI model is consists up of the subsequent layers: the physical, data link, network, transport, session, presentation and application. As one, these seven layers are jointly referred to as a stack. As a node receives data, each layer starting with the physical layer hauls out the different portions of the packet and this process works its way up to the application layer. When data is sent, it begins at the application layer and travels down to the physical layer.

The information is passed on to the next layer of the stack through commands called primitives. Every layer uses a peer protocol to enter the information, which makes sure that the same layer on the receiving node is capable to comprehend the information. (Twiggs, 2000)

2) Describe the three stages of standardization

The importance of having standards is to provide a “fixed” way for hardware and/or software systems (different companies) to communicate it also help promote competition and decrease the price. There are two types of standards, the formal and de-facto standards. The formal standards are those developed by an industry or government standards-making body while the latter emerged in the marketplace and are widely used, at some point; it lacks official backing by a standards-making body. The formal standardization process has three states: specification, identification of choices and acceptance.

The specification state involves developing the nomenclature and identifying the problems to be addressed, the second state involves identifying solutions to the problems and choosing the “optimum” solution, this state is called the identification of choices. The third and final state is acceptance that involves defining the solution, getting it recognized by industry so that a uniform solution is accepted. (Fitzgerald & Dennis, 2005)

3).  Explain how instant messaging works.

Instant messaging is consists of two software components, the server and the client software. Some IM programs can operate through an Internet browser, while some may require installation of client software on the user’s personal computer. The registered user’s directory is maintained by the server software and serves as a switchboard for communications traffic. In most cases, every character of instant messages routes through the IM server. For particular server connections, the client software should be installed in the user’s computer.

The identity of the user is either registered upon first connection to the server or is set-up by a system administrator. Users may input additional information about themselves in the directory of the user’s IM server depending on the system configuration. The user has a username and a password to log, and has the option to store the password permanently for automatic server connection once IM software startup. When user is active, it connotes successful connection, and then the user can select other users to list in the “buddy list”.

The client software installed on the user's computer is configured for particular server connections. The user's identity is either set up by a system administrator or registered upon first connection to the server. Depending on the system's configuration, users may input additional information about themselves into the IM server's user directory. The user logs in with username and password; the user may opt to have his or her password permanently stored to allow automatic server connection upon IM software startup.

Successful connection to the server lists the user as active (unless the user changes status), and he or she may select other users to list in the "buddy list." The status of buddy list users is then displayed. From this point, the user is free to exchange messages; some IM software also allows users to transfer pictures and electronic files. (http://findarticles.com, 2003)

4. Some experts argue that thin-client client-server architectures are really host-based architectures in disguise and suffer from the same old problems. Do you agree? Explain.

A way to classify client/server architecture is on how much of the application logic is located on the client. A thin client does little tasks related to logic application. The wide use of this client is the World Wide Web, for recently web-enabled applications are developed which allows access to the application using only the Web browser. Some features of the thin client are the following: no required software distribution, cross compatibility by means of standard protocols, establishes server connection on little action, no immediate feedback, limited GUI options and HTTP is connectionless protocol.

Thin-client and client-server architectures are not disguised as host-based, because in both architectures, there are sharing of network processes whereas there is  none in the host-based architecture. (Hohpe, 1998)

5). Investigate the use of the three major architectures by a local organization (e.g., your university.) Which architecture(s) does it use most often and what does it see itself doing in the future? Why?

In networking, there are three architectures, which are; host-based, client-based, and client/server architectures. Host-based architecture is used in early data communication networks, the host as the mainframe perform all the functions of data management, the client here is usually a terminal, the downside of this architecture is the host handling all the processes, and slowing-down of network is experienced when there are many processes being handled. The only solution is a host upgrade which is rather expensive.

This paved way for the use of Local Area Connection, which is client-based architecture. In this architecture, the client performs the data functions and the host simply stores the data. Network circuit capacity is involved to process the number of data and in some way network performance decreases. A solution for such is the client/server architecture. In a client/server architecture, there is sharing of the processing. The client carries out the presentation logic and the server performs the data access and storage.

Servers are easy to upgrade and at low costs when the demand for processing and storage increases on the network. Users have the options to select the types of client and operating systems that they like to use. Since applications can run on different servers, the reliability on network increases. There are no chances to arrive at failure compared to host-based. It also allows software and hardware from various manufacturers on the same network to work together.

(Department of MIS, University of Illinois, Springfield, 2003) Nowadays, organizations opt to have the client/server architecture since more processes are needed to be carried out simultaneously. Efficient network performance in data management is required for the organizations functions, because of which, more and more organizations would rely on client/server architecture in the future.

Reference:

Department of MIS. (2003). Telecommunications, University of Illinois at Springfield.

Dennis A. & Fitzgerald J. (2005). Business Data Communications and Networking

8th Edition, John Wiley & Sons, Inc.
Hohpe, G. (1998). Are Your Clients Overweight?

 Software Architectures for the Internet Age,

FITO, Deloitte and Touche Consulting.

Information Management Journal. (2003). How instant messaging works. Retrieved January 9,                 2008, from http://findarticles.com.

Twiggs. W. (2003). An Introduction to the OSI Model and Layered Communications. Retrieved

January 9, 2008, from http://www.comtest.com/tutorials/osi.html.