NTC360 Week 3 Discussion Questions
...e that if entrants are permitted to compete for these services, competitive market forces are and will continue to be fully capable of bringing the benefits of the information age to all parts of the country. o The “last mile” bottleneck there is today an abundance of Internet backbone facilities in this country — provided by over 45 different firms; indeed, the media has recently speculated that there may actually be too much capacity. The problem with gaining access to the Internet is in the “last mile” — the euphemism that is commonly applied to describe the telecommunications link between the customer’s premises and the point at which a connection to the public network is made; that “last mile” may often be — and in the case of rural customers almost always is — a good deal longer than one mile. Traditionally, the “last mile” access link was provided using a separate twisted pair of copper wires dedicated to each individual subscriber. Various new technologies have altered the access link service arrangement, with the choices depending heavily upon the physical distance between the customer and the network access point, and the character of the terrain over which this access link must travel. What are the prospects for broadband globally? o The growth of broadband Internet is accelerating, reports the United Nations-backed International Telecommunications Union. o The number of global broadband subscribers grew 72 percent in 2002, says the ITU, with the Republic of Korea, Hong Kong, and Canada leading the way. Korea has 21 broadband subscribers for every 100 inhabitants, and one in ten Internet users worldwide has a dedicated broadband connection, the organization claims. o Tim Kelly, ITU head of the strategy and policy unit, said: "Broadband is arriving at a time when the revolutionary potential of the Internet has still to be fully tapped. However, while broadband is accelerating the integration of the Internet into our daily lives, it is not a major industry driver in the same way that mobile cellular and the Internet were in the 1990s. It's an incremental improvement, offering Internet access that is faster, more convenient, and cheaper than ever before." • Use short answers to explain the difference between: Synchronous and asynchronous o Synchronous and Asynchronous transmission are two different methods of transmission synchronization. Synchronous transmissions are synchronized by an external clock, while asynchronous transmissions are synchronized by special signals along the transmission medium. o The send, receive, and reply operations may be synchronous or asynchronous. A synchronous operation blocks a process till the operation completes. An asynchronous operation is non-blocking and only initiates the operation. The caller could discover completion by polling, by software interrupt, or by waiting explicitly for completion later. (Does it make sense to have an RPC send not block?) An asynchronous operation needs to return a call/transaction id if the application needs to be later notified about the operation. At notification time, this id would be placed in some global location or passed as an argument. Analog and digital o "Analog" refers to information being presented continuously, while "digital" refers to data defined in individual steps. Analog information's advantage is its ability to fully represent a continuous stream of information. Digital data, on the other hand, is less affected by unwanted interference, or noise. In digital computers, data is stored in individual bits, which have a value of either 1 (on) or 0 (off). If graphed, analog signals are shaped as sine waves, while digital signals are square waves. Sound is analog, as it is always changing. Thus, in order to send information over a phone line, a modem must take the digital data given it by the computer and convert it into sound, an analog signal. The receiving modem must convert these analog signals back into the original digital data. XON and XOFF o XON/XOFF are special characters sent over the serial link and do not require additional wires. XOFF is the character CTRL-S (ASCII code 19) and XON is the character CTRL-Q (ASCII code 17). For example, if you connect two computers with a serial cable and are able to type characters on one computer and see the characters appear on the other computer -- press CRTL-S (XOFF) on one computer to stop communications. Type on the other computer and you should see that the characters are not transmitted. Once you press CTRL-Q (XON) the characters should show up because they were held at the transmitting computer until XON was sent by the receiving computer. Simplex and duplex o Simples: When people use walkie-talkie radios to communicate, only one person can talk at a time (the person doing the talking has to press a button). This is because walkie-talkie radios only use one communication frequency. o For example - Simplex: Using a walkie-talkie you have to push a button to talk one-way. o Of course, this is not how mobile phones work. Mobile phones allow simultaneous two-way transfer of data - a situation known as duplex (if more than two data streams can be transmitted, it is called multiplex): Serial and parallel transmission o These bits which represent humanly-readable characters can be transmitted in either of two basic transmission methodologies. They can be transmitted either simultaneously (parallel transmission) or in a linear fashion, one after the other (serial transmission). The advantages, limitations and typical applications of each transmission methodology are summarized below. Transmission Characteristic Serial Parallel Transmission Description One bit after another, one at a time All bits in a single character transmitted simultaneously Comparative Speed Slower Faster Distance Limitation Farther Shorter Application Between two computers, from a computer to an external modem, from a computer to a relatively slow printer Within a computer along the computer's bus, from a computer to parallel high speed printers Cable Description All bits travel down a single wire, one bit at a time Each bit travels down its own wire simultaneously with other bits. Baseband and broadband o Data signals can be sent over a network cable in one of two ways: broadband or baseband. One good example of broadband signaling would be how you view different channels through your cable box and a signal coaxial cable carrying multiple signals in cable television. Whereas, baseband signaling only sends a single signal over the cable. This t...