Digital Communication System - Assignment Example

Description: An assignment about internet/web covering the topic with respect to its introduction, explanation, benefits, limitations, recommendations to improve. Introduction A communication system is a tool for interaction between two entities. It is a way to establish, prove, convey and share ideas. A normal talk between two people is also a communication system in its crude form. Technically, a communication system is classified into 2 types: Fig.: Communication types A digital communication system essentially needs less power as compared with analog system. It is faster and has several advantages in terms of providing a better signal to noise ratio over the same bandwidth. Over a period of time, along with the evolution of human species has evolved its comfort tools such as clothing, transportation, communication, defense equipments, etc. For all of us who stick to internet daily and can’t move ahead without its extended support it becomes necessary to know the intricacies of internet. Today the world has come much closer with the advent of internet and cellular communication systems. The cultural, lingual, technological, political, ethical and intellectual gap is being bridged because of these tools. People from different topographical regions have virtually come very close to each other. The following assignment deals with “internet” as a digital communication system. Keywords: analog, digital, internet, protocol, system, network, packets, hardware, server, ISP, TCP/IP, web components, layers, performance, cache, download Internet is an interconnection of networks. It isn’t just one network but a multitude of networks connected to each other through wired or wireless signal transmission systems. A very commonly asked question about internet is: Who runs it? The truth is that there is no centralized management. Instead it is a collection of thousands of individuals and organizations each of which is run and paid for on its own. (Gralla et al, 1998) Here we can imagine the chaos that can be caused due to improper co-operation amongst bearers and users of internet! Hence to have proper functioning of entire system, a set of rules has been defined for communication to take place. This set of rules is known as Transmission Control Protocol/Internet Protocol (TCP/IP). When we send information across the internet, the information first breaks into packets. Our computer sends these packets to the local area network or Internet Service Provider (ISP). The packets then travel through many levels of networks, computers and communication lines before the final destination which could be anywhere in the world. A variety of hardware and array of network layers process these packets. Five of the most important pieces of hardware are: Fig.: Internet hardware HUBS: Link groups of computers to one another establish communicate between them. BRIDGES: Link local area networks to one another. They enable data designed for another LAN (Local Area Network) to be sent there while simultaneously keeping the local data inside its own network. Gateways: Similar to bridges; responsible for transfer of data between different kinds of network. REPEATERS: The signal travels large distances across networks. While traveling, the data is vulnerable to get lost or signal might weaken. To prevent this from happening or to recover weak signals repeaters are used at regular intervals to amplify signals. ROUTERS: Routers ensure that data packets reach their respective destinations. Routers aren’t needed for data transmission between same LAN. They are usually required for communication between different networks. LANs are often hooked together using high speed telephone lines (1.544Mbps), Ethernet and microwave links. Many LANs together form a WAN (Wide Area Network). Working of TCP/IP: Step 1: Internet is a packet switched network. Information across the internet is broken down into small packets. Breaking the data into packets, routing packets across internet (done by IP) and recombining them at the other end (done by TCP) comprise the first step. Step 2: The packet size should be limited because of various reasons including limited hardware capacities. Each packet is given a header that contains a variety of information such as the order of packets. As TCP creates each packet, it calculates and adds to the header a checksum, which is a number used at the receiving end to determine error occurred during transmission. Step 3: Each packet is put into separate IP network which contains the addressing information that tells the internet where to send the data. Envelopes for given data have same addressing information for ease of reassembling at receiving end. Every IP address consists of four numbers separated by periods called dots. Step 4: The DNS (Domain Name Server) is used to convert textual internet address into IP numeric equivalent. DNS establishes a hierarchy of domains, which are groups of computers on the internet. Domain name and hostname consist of information about host computer, information about organisation which identifies the recipient network and the specific email box.(Gralla et al, 1998) A generalized web connection consists of following blocks: Fig.: Components in a web connection 1. PC: It acts like a command and control station that navigates the web. It has to have installed web browser software and integrated communication program. It is hooked to a modem. 2. Modem: It basically carries out modulation and demodulation of outgoing and incoming signals respectively. It takes data from PC and transfers it to the telephone line. Modulation is carried out to enable data compatibility while travelling on telephone lines. Similarly demodulation of incoming signals is essential for PC to recognize the data. Alternatives to modem: PDAs (Personal Digital Assistants), Web TV, cable modem, etc. 3. Telephone line: It carries signals between modem and ISP (Internet Service Provider) 4. ISP: It is the authorized point which provides internet connectivity to its customers. 5. Internet: Beyond ISP there is a huge network of networks connected to each other in some fashion. ISP enabled access to these networks and information therein. Network layers in TCP/IP reference model: The ability to connect multiple networks in a seamless way was the major design goal to establish effective communication networks. The TCP/IP model defines 4 layers: Fig.: TCP/IP reference model 1. Physical layer: The TCP/IP reference model does not really say such about what happens at the physical layer except that the host connects to the network using some protocol to transmit IP packets over it. This protocol is not specified and varies from host to host and network to network. 2. Network layer: Packet switching network depends upon a connectionless internetwork layer. This layer is known as internet layer. Its job is to allow hosts to insert packets into any network and have them to deliver independently to the destination. They may appear in a different order than they were sent in each case it is job of higher layers to rearrange them in order to deliver them to proper destination. The internet layer specifies an official packet format and protocol known as internet protocol. The job of internet layer is to transport IP packets to appropriate destination. Packet routing is very essential task in order to avoid congestion. 3. Transport layer: The layer above the internet layer is known as transport layer. It is developed to permit entities on the source and destination hosts to carry on a conversation. It specifies 2 end-to-end protocols: a. TCP (Transmission Control Protocol): It is a reliable connection-oriented protocol that permits a byte stream originating on one machine to be transported without error on any machine in the internet. It divides the incoming byte stream into discrete message and passes each one onto the internet layer. At the destination, the receiving TCP process collects the received message. TCP deals with flow control to make sure a fast sender cannot swamp a slow receiver with more message than it can handle. b. UDP (User Datagram Protocol): It is an unreliable, connectionless protocol for applications that do not want TCP’s sequencing on flow control and wish to offer their own. It is also used for client-server type request-reply queries and applications in which prompt delivery is more important than accurate delivery such as transmitting speech or video. 4. Application layer: Application layer is present on the top of the Transport layer. It includes all the higher-level protocols which are virtual terminal (TELNET), file transfer (FTP), hyper text transfer protocol (HTTP), electronic mail (SMTP) and simple network management protocol (SNMP). The virtual terminal protocol permits a user on one machine to log into a distant machine and work there. The file transfer protocol offers a way to move data efficiently from one machine to another. Electronic mail was used for file transfer purpose but later a specialized protocol was developed for it. HTTP permits applications such as browsers to upload and download web pages. SMTP sends email to other computers that support the TCP/IP protocol suite. SNMP is used as standardized protocol. Managed network devices can be cross examined by a computer running to return details about their status and level of activity. (Paluri 2004) Benefits and Limitations of Internet: Internet has become an obvious choice when doing research. Like any tool it also has unique characteristics that create both benefits and drawbacks. Benefits: 1. Access to new and valuable sources of information that came into being because of the Internet. These include electronic journals (e-journals) and Internet discussion groups. 2. A more efficient route for accessing certain standard information sources such as newspapers, particularly overseas papers and electronic versions of existing print journals. 3. Access to non-mainstream views. Fringe groups and those without access to the media or a printing press can now make their opinions known on the Internet. 4. Access to digitized versions of primary sources. Some libraries are digitizing (making electronic versions) of primary research sources such as personal letters, official government documents, treaties, photographs, etc. and making these available for viewing over the Internet. The same is true for audio and, in some cases, video. 5. Access to government information. The U.S. federal government is one of the largest publishers in the world and it is utilizing the Internet as its preferred method for disseminating much of its information. 6. Speed and Timeliness: Doing a search on the Internet can take just seconds. On the Internet you can find information that has just been made available a few minutes earlier. 7. Multimedia: The Internet delivers not just text, but graphics, audio, and video. 8. Hyperliking: The ability to click between Web pages can facilitate an associative type of research, and make it easier to view citations and supporting data from a text. (Ko, M) Limitations: 1. Diverse collection of information: The diversity makes it difficult to separate out and pinpoint just the type of information that one wants. 2. Difficult to search effectively: A traditional electronic database that you might search in a library may take a little learning and practice, but once you get the hang of it, you can become an effective searcher. But on the Internet, even if you know all the ins and outs of searching, because of the built-in limitations of Internet search engines and the way Web pages are created, you'll only be able to search a small percentage of what's on the Net. You also won't be able to easily distinguish the valuable from the trivial pages; and you can obtain unpredictable results. 3. Lack of context: Because search engines will return just a single page from a multipage document, you can miss the larger context from which that information was derived. 4. Lack of permanence: Web pages are notoriously unstable. They appear, move, and disappear regularly. This can be of particular concern for academic researchers, who need to cite a stable page for reference purposes. 5. Selectivity of coverage: Despite the size of the Internet, the vast majority of the world's knowledge still resides in print. So a search for information on the Internet in no way represents a comprehensive search of the world's literature or knowledge. 6. A good deal of what's on the Internet is "off-limits" to search engines and is not retrievable. These off-limit sites include those that are accessible only to those who register, input a password, or pay a subscription fee. In all, one can see that researching on the internet can be a blessing or an impediment for good research results. But doing some research on the internet can, at least, provide a good foundation for your researching endeavors. (Ko, M) Recommendations to improve internet services: 1. A PC can tell the speed capacity of the DSL but not that of Internet. Sometimes, it should correct and pick up speed. Selecting a good Internet Service Provider is very important. There is a serious competition amongst the ISPs offering broadband connections. Testing the broadband speed can offer some solution to pick the right service provider as it gives you an idea of your bandwidth as well as your real connection speed. It also tells the throughput of your connection (amount of data that can be transferred at any point of time). (Knuden, J 2007) 2. The architectures in terms of OSI or TCP/IP reference model have already been established. Deep thought and analysis of existing implemented systems can give us an insight into improvements that can be done to further enhance internet services. 3. For improved connectivity, one should get rid of modem and switch to ADSL which is known to offer broadband connection by means of a dedicated subscriber line thus improving data transfer speed. In case we are using a modem, we should update the driver files and make sure that these are suitable for our operating system. The software in the modem should also be upgraded periodically for better performance. (Chandler, K) 4. The internet is much faster if the rest of the world is asleep. The speed of internet is very much a function of its load. More the load, more the amount of time it takes to serve each one of them. Hence using internet when probable load is lesser can give good results. 5. FTP is much suitable for file transfers than HTML. So, wherever needed and possible use of FTP should be implemented. 6. Use of a download tool: There's nothing more frustrating than losing a connection near the end of a one hour download. The good news is that most downloads are resumable which means they can be restarted from where the connection failed. The right tool should be available to manage the reconnection. (Chandler, K) 7. Manage cache: Every time we use the internet, images and other files are downloaded onto the hard disk. If a particular image or other file is needed in a subsequent session, it can be pulled from the disk faster than it could be downloaded again. They are kept in a "Temporary Internet Files" folder, often called Cache. When the folder is full, Windows deletes the oldest files. By varying the size of this folder, a good service can be managed. (Chandler, K) Such and other means can be discovered and devised to improve on our internet connection. Today internet has become an inseparable part of our lives. Let us make an effort to understand it better each time that we hook on to it and improve it for our betterment to have unobstructed progress. References: Gralla, P, Ishida, S, Reimer, M & Adams, S 1998, How the Internet Works, Que Publishing, pp. 5, 9, 14, 17, Available from: google books. [24 March, 2009] Ko, M, Benefits and Drawbacks of the Internet as a Research Source, Available from < http://www.articlegarden.com/Article/Benefits-and-Drawbacks-of-the-Internet-as-a-Research-Source/5346> [24 March, 2009] Paluri, R 2004, TCP/IP Reference Model, Available from: buzzle.com < http://www.buzzle.com/editorials/8-24-2004-58325.asp> [24 March, 2009] Knuden, J 2007, Best Ways To Improve Internet Speed, Available from: [25 March, 2009] Chandler, K, Top tips to improve your internet connection! How to squeeze the most from your modem, Available from: [25 March, 2009] Read More