How a message is transmitted from one computer to another one using layers
Two computers communicate when they are in a computer network. For such a network to exist the computers are either connected either through a physical medium such as an Ethernet cable or through a wireless network that uses electromagnetic or radio waves. Another factor that is important to consider when determining the communication of computers in a network is the type of software used. A computer network can operate with either of these two types of operating systems. These are Open System Interconnection (OSI) or Internet Protocol (IP). In this discussion, we are going to focus on the transmission of information in the OSI model. (O’Brien, J. A., & Marakas, G. M. 2008, 98)
A series of seven layers that perform their respective duties sequentially controls the transmission of information in an OSI model. These layers consist of:
Physical layer
This layer is also referred to as layer I. This layer is responsible for determining how the binary bits that comprise the message being transmitted are controlled. This involves determining the voltage and frequency at which the transmitted message will be relayed from one computer to the other. Then it retransmits this message to the data layer. (O’Brien, J. A., & Marakas, G. M. 2008, 102)
Data layer
The data layer also known as layer 2 receives the message transmitted from layer 1. It determines these data limits. That is where it starts and ends. Hence it identifies any errors present in this message and corrects them accordingly before transmitting this message to the Network layer.
Network layer
It determines the destination address of the message being transmitted and gives it the right routing to the required computer over the network.
Transport layer
Message from the Network layer is transmitted over to the Transport layer where error detection is done once more. Then large streams of data are broken down into smaller packets. Packets of data that have been duplicated are eliminated before the data is transmitted to the session layer.
Session layer
Is responsible for initiating, sustaining, and stopping logical sessions when a stream of the message is being transmitted from one computer to another one. From here the data is retransmitted to the Presentation layer.
Presentation layer
This layer formats the transmitted message. Its work is to allow formatting and displaying of the transmitted message in a manner that enables the various interfaces.
Application Layer
From the presentation layer, the message is transmitted to the Application layer where it enables access of the message to the end-user. The transmitted message is given appropriate application programs to enable the end-user to receive the message.
Describe the three stages of standardization
All standards originate from vendors as protocols they use to regulate certain operations in their organizations. After some time the vendors issue a suggestion to the Internet Engineering Task Force (IETF) to standardize their protocols. The IETF then organizes a team of experts that studies the proposed protocols and writes a report of their findings to the IETF. If the report is positive, the IETF then Requests For Comments from all over the world. Internet users and most of the big software companies that are most likely to be affected by the proposed write their reports to the IETF. The IETF then studies their responses and recommends appropriate modifications to the proposed standards. Then avails the RFC. This process is done until all parties affected are comfortable and then IETF standardizes the proposed standards.
Explain how instant messaging works
Instant messaging Is an Internet technology that lets you receive messages, attachments, and other data moments after they’re sent. Instant messaging isn’t a toy anymore. While IM started as a way to chat with friends, technology is becoming an essential tool for business. It offers the convenience of e-mail and the immediacy of a phone call, as well as files transfers and voice messaging. IM is the newest way to keep in touch. Instant messages are characterized by:
- Messages arrive in real-time because both parties are constantly connected to the network.
- Expect instant messages everywhere
- You can send files and voice messages as well as text messages.
- A lack of standards means you can communicate only with others who use the same messaging service.
The “instant” in instant messaging is possible because the people sending and receiving messages remain constantly connected to their IM service. Recipients get messages as fast as the data can travel across the Internet. E-mail, on the other hand, is less immediate. E-mail technology sends messages to a server that stores the items until they are downloaded by the recipient’s e-mail software.
How Instant Message Works
When you log on to an IM service, the software lets a server know you’re available to receive messages. To send a message to another online user, you begin by selecting that person’s name, usually from a contact list you’ve built. You then enter your message and click Send. The sent packet contains address information for the recipient, the message, and data identifying you as the sender. Depending on which service you use, the server either directly relays the message to the recipient or facilitates a direct connection between you and the recipient. Unfortunately, because there is no standard instant messaging protocol, you can send messages only to people who are logged on to the same service as you are. If you’re using AOL Instant Messenger, you can’t chat with someone who uses ICQ’s messaging software. (David 2001, 8)
Instant Messages services use three means to move messages around: a centralized network, a peer-to-peer connection, or a combination of both. In a centralized setup, users are connected to each other through a series of servers. These servers link to form a large network. When you send a message, servers find your recipient’s PC and route the message through the network until it reaches its destination. IM services such as MSN Messenger use this method. In the peer-to-peer approach used by ICQ, for example, a central server keeps track of who is online and what their unique Internet Protocol addresses are. (An IP address identifies a computer so it can send and receive data via the Internet.) After you log on, the server sends you the IP addresses of everyone on your contact list that is currently logged on. When you want to send a message to another ICQ user, your client sends it directly to the recipient’s client, without involving the server. Messages don’t go through the entire network. This speeds transfers of large files such as documents and photos because network traffic doesn’t slow them. (David 2001, 112)
AOL’s AIM combines the centralized and peer-to-peer methods. When you send a text message, it travels along with AOL’s centralized network. However, when you transfer files, pictures, or voice messages, the clients establish a peer-to-peer connection.
The instant messaging biggest problem remains its lack of standards. In the world of e-mail, you can send a message to anyone who has an e-mail account, regardless of which service or software they use. But you can’t do that with instant messaging, because each service uses a proprietary protocol and network. If you’re signed on with AIM, you can chat only with other AIM users. (David 2001, 8)
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 thin client sometimes also called a lean client is a client computer or client software in client-server architecture networks, which depends primarily on the central server for processing activities, and mainly focuses on conveying input and output between the user and the remote server. In contrast, a thick or fat client does as much processing as possible and passes only data for communications and storage to the server. Many thin client devices run only web browsers or remote desktop software, meaning that all significant processing occurs on the server. However, recent devices marketed as thin clients can run complete operating systems such as Debian GNU/Linux, qualifying them as diskless nodes or hybrid clients.
As a consequence, the term “thin client”, in terms of hardware, has come to encompass any device marketed as, or used as, a thin client in the original definition even if its actual capabilities are much greater. The term is also sometimes used in an even broader sense, which includes diskless nodes. Thin client as an application program communicates with an application server and relies for most significant elements of its business logic on a separate piece of software, an application server, typically running on a host computer located nearby in a LAN or at a distance on a WAN or MAN. A thin client does most of its processing on a central server with as little hardware and software as possible at the user’s location and as much as necessary at some centralized managed site. (Amos 2001, 97)
A thin client as a device is designed to provide just those functions that are useful for user-interface programs. Often such devices do not include hard disk drives, which may become corrupted by the installation of misbehaved or incompatible software, but instead, in the interests of low maintenance cost and increased mean time between failures (MTBF) the thin client device will use read-only storage such as a CD-ROM, Network Virtual Drive or flash memory. Ideally, the user will have only a screen, keyboard, a pointing device (if needed), and enough processing power to handle display and communications. Numerous companies develop and market these devices. The thin client design is host-based. This is because in this design most of the computer’s operations are restricted to the server similar to how a host-based architecture operates. Therefore I highly concur with the statement that thin-client architectures are host-based architectures. (Amos 2001, 68)
Investigate the use of the three major architectures by a local organization (e.g., your university or your choice). Which architecture(s) does it use most often and what does it see itself doing in the future? Why?
There are three types of application architectures. These are:
- Host-based networks
- Client-based networks and
Client-server network
In a host-based network, all the execution are done by the server. All the terminals that serve as the client send their requests to a common central server that execute all the operation. This makes the server receive many requests to execute at any instant time, which slows down the speed of this network. This method was common in old days as the method of processing data in universities where all processing was restricted to a central location. This was a slow and very inefficient way of processing data. This process was then replaced by the client-based network. (Amos 2001, 69)
The client-based network used the client computers for application programs, presentation logic, and data access logic. In this network, the server was used to store the data being processed by the client computers. This type of network was common in many institutions such as universities for storing and processing students’ data. The server that is centrally located kept all the students’ records that were regulated updated by the client computers located in the administration, academic and financial departments accordingly. This network has now been replaced by the client-server network.
The client-server network allows the client and the server to share executions. The server acts as the central point that allows access or communication between two or more computers. The server determines the information to be shared over the network and denies access to sensitive files and documents. This type of network is commonly used in many universities. Local Area Network and Metropolitan network in many universities are operating using this type of network to share information of students and workers within the universities departments and also among the universities campuses. (Boniface 2004, 123)
Many universities have used this type of architecture to allow long-distance learning and the others that have not yet are in the process of doing so. In long-distance learning students enroll online and receives their learning material online through CD or videoconferencing.
1. Computers produce and transmit digital data or information. Digital data is composed of a stream of ‘1’ and ‘0’. On the other hand, the sound is transmitted in analog form over telephone lines. Therefore the information that is produced by computers is digital and cannot be relayed through the telephone in this manner. Therefore a modulating modem is used to convert the digital data into analog form for it to be transmitted over the telephone line. This information is transmitted in this form when it reaches its destination it is converted back to its digital form by a demodulating modem. Charles 2005, 130)
The time that will be taken to transfer files in Atlanta is less than the time taken to transfer bits because files are moved faster than bits.
Yes it is possible for the NDAS to transmit it’s to Tampa between 5.P.M and 6.P.M. This can be achieved by transmitting the invoices as files instead of bits.
References
Amos H. (2001) Network Architecture; Prentice Hall: New York. Pgs 67-100.
Boniface M. (2004) Host-Based networks: Oxford University Press: London. Pgs 123-134.
Charles W. (2005) Modulation and Demodulation of Data; Oxford University Press: London. Pgs 16-134.
David T. (2001) Instant Messages: Oxford University: London pgs 101-112.
O’Brien, J. A., & Marakas, G. M. (2008) Management information systems Boston: McGraw-Hill/Irwin. Pgs 97-107.