MI361 Ch10 Review Questions
How does a DSL modem differ from a DSLAM?
A DSL modem produces Ethernet 10Base-T packets so it can be connected directly into a computer or router and hub so that it can serve the needs of a small network. The DSLAM de-multiplexes the data streams and converts them into ATM data, which are then distributed to the ISPs.
What is a POP?
A POP is an acronym for "point of presence." The POP is the place at which the ISP providers services to its customers.
Explain how ADSL works.
ADSL is the most common type of DSL used today. It uses frequency division multiplexing to create three separate channels over the one local loop circuit. One channel is the traditional voice telephone circuit, the second channel is a relatively high-speed simplex data channel, and the third channel is a slightly slower duplex data channel.
What is an OE converter? A CMTS?
An OE is an optical-electrical converter, which converts between the coaxial cable on the customer side and fiber-optic cable on the cable TV company side. The CMTS contains a series of cable modems/multiplexers and converts the data from cable modem protocols into protocols needed for Internet traffic, before passing them to the router connected to an ISP POP.
Explain how DSL works.
DSL requires equipment that is installed at the end of the cable (within the house or office) which allows traditional telephone service (POTS) to take advantage of much higher data transmissions rates via the existing cable in the local loop.
Explain one reason why you might experience long response times in getting a Web page from a server in your own city.
If the other organization uses a different local ISP, which in turn uses a different regional ISP, the message may have to travel all the way to the Chicago IXP before it can move between the two separate parts of the Internet.
Compare and contrast cable modem and DSL.
Individuals connect to ISP's mostly via DSL and cable modems today. The speeds vary between the two technologies and it depends on location and provider as to which is faster. One of the main differences between the two is that DSL customers have a direct connection back to the end office with point-to-point technology, whereas cable modems use shared multipoint circuits.
What is an IXP?
Internet Exchange Points are connection points between Internet Service Providers.
What is Internet2®?
Internet2® comprises about 400 universities, corporations, government agencies, and organizations from more than 100 countries with a primary focus to develop advanced networking as well as other innovative technologies for research and education.
Explain how WiMax works.
Mobile WiMax works in much the same way as Wi‐Fi. The laptop or smart phone has a WIMAX network interface card (NIC) and uses it to establish a connection to a WiMax access point (AP). Many devices use the same AP so WiMax is a shared multipoint service in which all computers must take turns transmitting. Media access control is controlled access, using a version of the 802.11 point coordination function (PCF). WiMax uses the 2.3 GHz, 2.5 GHz, and 3.5 GHz frequency ranges in North America, although additional frequency ranges may be added.
How is the IETF related to the IRFT?
The ISOC comprises of four bodies that act together to govern, IETF and IRFT are two of the four.
What is the principal American organization working on the future of the Internet?
The Internet Society is an open-membership professional society with about 150 organizational members and 65,000 individual members in more than 100 countries, including corporations, government agencies, and foundations that have created the Internet and its technologies. Because membership is open, anyone, including students, is welcome to join and vote on key issues facing the Internet. Its mission is to ensure "the open development, evolution and use of the Internet for the benefit of all people throughout the world." It works in three general areas: public policy, education, and standards.
What is the basic structure of the Internet?
The Internet is hierarchical in structure. At the top are the very large national Internet service providers like AT&T, Sprint, etc. with regional and local internet service providers reporting up through this hierarchy.
Explain how the Internet is a network of networks.
The Internet was originally run by the U.S. National Science Foundation (NSF), but now the NAP's are commercial enterprises run by various common carriers. These NAP's are connected to other NAP's, who have several ISPs attached, who have regional ISPs attached to them, who have consumers attached to them. This spider web branches out into countless networks all over the world. There are agreements between the carriers to enable the exchange of messages, with varying payment mechanisms.
Explain how a cable modem works.
The cable modem works very similar to DSL, with one very important difference, DSL is a point-to-point technology, whereas cable modems use shared multipoint circuits. Cable modems must compete with other users for the available capacity. Circuits that have many clients are thus slower than circuits with fewer circuits.
What are some future technologies that might change how we access the Internet?
The next big technologies are Passive Optical Networking and Internet 2.
Which is better, cable modem or DSL? Explain.
The speeds for each of these has increased significantly over the past few years. In most cases, you need to check with the local service providers to see what speeds they offer.
Explain how FTTH works.
The traditional set of hundreds of copper telephone lines that run from the telephone company switch office is replaced by one fiber‐optic cable that is run past each house or office in the neighborhood. Data is transmitted down the signal fiber cable using wavelength division multiplexing (WDM), providing hundreds or thousands of separate channels. At each subscriber location, a Optical Network Unit (ONU) (also called an Optical Network Terminal (ONT)) acts like a DSL modem or cable modem and converts the signals in the optical network into an Ethernet format. The ONU acts as an Ethernet switch and can also include a router. FTTH is a dedicated point‐to‐point service like DSL, not a shared multipoint service like cable modem.
Many experts predicted that small, local ISPs would disappear as regional and national ISPs began offering local access. This hasn't happened. Why?
There are technology changes made every day, which requires all ISP providers constant change. There have been some consolidation recently, but with all the change underway, what would the larger companies really be purchasing.
Today, there is no clear winner in the competition for higher-speed Internet access. What technology or technologies do you think will dominate in 2 years' time? Why?
There is no answer for this, as technology changes day by day; however, I think Internet 2 development is definitely something to watch.
What are the principal organizations responsible for Internet governance, and what do they do?
There is no one organization that operates the Internet. The closest thing the Internet has to an owner is the Internet Society (ISOC). This is an open membership professional society with more than 175 organizational and 8,000 individual members in over 100 countries. The ISOC mission is to ensure "the open development, evolution and use of the Internet for the benefit of all people.
What is a gigapop?
These are new points-of-presence (POP) that work at gigabit speeds.
Would you be interested in subscribing to 100 Mbps FTTH for a monthly price of $100? Why or why not?
This answer depends on the options that you currently have and the amount of uploading and downloading you actually perform. Many locations offer DSL and/or cable access for $30 per month with data rates up to 15 Mbps. Obviously increasing the download rate to 100 Mbps would provide a much faster connection, but at more than double the price. For those users who use email and do some light browsing, then the increased speed may not provide enough benefit. For those who are heavy users (file sharing, watching movies online, playing games, etc), the increased cost would be well worth it.
What type of circuits are commonly used to build the Internet today? What type of circuits are commonly used to build Internet 2?
Today, the backbone circuits of the major U.S. national ISPs operate at SONET OC-192 (10 Gbps). Internet 2 will consist of circuits at least at OC-192 levels, with OC-768 (80 Gbps) and possibly even OC-3072 (160 Gbps) available.
