CS 363

Winter 1999

Homework 1

 

Instructions:

  1. This homework is to be completed on your own, with no help from classmates or friends. Use all books and websites you can find as resources.
  2. This homework is due at 12noon on Thursday, 21 January, 1999.
  3. Completed homeworks should be e-mailed to cs363@sadler.atd.depaul.edu Homeworks can appear in plain text as the body of the mail message or as an attachment. I can read Word ’97, html, and rtf formats.
  4. Homework answers will be posted to the class website at the due time, so no late assignments will be accepted.

Problems:

  1. (10 points) Your company has just decided to install a network for the first time. You have been asked to specify configurations for your 120 servers. Because of heavy data load anticipated on the network, it’s essential that the servers keep up with significant amounts of traffic. Your manager has asked you to put together a "killer server" to keep up with the demand.
    1. The required result and both of the optional desired results.
    2. The required result but only one of the optional desired results.
    3. The required result but neither of the optional desired results.
    4. The proposed solution does not produce the required results.

Answer: B. Because a 32-bit bus mastering NIC with additional onboard RAM gives you about as much speed as you can get when attaching a server to a cable segment, it definitely produces the required result of handling network traffic with reasonable response time. This also helps to guarantee that the server won't slow the network down. But since it would be cheaper (in fact half the cost) to use plain-vanilla NICs on the relatively idle segments, this solution fails to keep the hardware costs of a minimum. Thus the correct answer is b, which produces the required result but only one of the optional desired results.

 

  1. (10 points) An advertising firm decides to install a network to link all the employee’s computers together. The company plans to introduce some video teleconferencing software across the board and plans to use e-mail and database applications heavily. Because of the anticipated load on the network, you want it to be as fast as possible.
    1. The proposed solution delivers the required results and both of the optional desired results.
    2. The proposed solution delivers the required results but only one of the two optional required results.
    3. The proposed solution delivers the required results but neither of the optional desired results.
    4. The proposed solution does not deliver the required result.

Answer: B. The advertising firm's decision to use Category 5 wiring and hubs, presumably with 100 Mbps Ethernet, certainly delivers the required result, of providing a network that operates at speeds of up to 100 Mbps. Of all twisted pair cable varieties, however, Cat5 is the most expensive, so the cabling will not be as cheap as it gets—but to meet the 100 Mbps requirement, Cat5 is required, so this is one of those Microsoft questions that requires careful reading. The exact wording is "as inexpensive as it can be"—as long as you buy a reasonably-priced grade of Cat5 cable, this requirement cannot help but be met, despite appearances. As for ease of installation, only someone on-site can decide what's easy and what's not. However, professional TP cable installation usually requires wall plates and routing cables through ceilings and into walls. These fail to qualify as easy, unless you're a full-time cable installer. Therefore, the answer to this question is b, since the required result and only one of the optional desired results is met.

 

  1. (10 points) Berts, Inc., has decided to bring mobile computing to its field engineers. Each field engineer is to be supplied with a laptop, a portable fax/printer, and some kind of wireless transmission device.
    1. The proposed solution delivers the required result and both of the optional desired results.
    2. The proposed solution delivers the required results and only one of the two optional desired results.
    3. The proposed solution delivers the required results but neither of the optional desired results.
    4. The proposed solution does not deliver the required result.

Answer: B. Berts’ quest for mobile computing for its field engineers depends on use of cellular modems to connect remote computers with the organization's LAN. Because the plan also includes encryption fees, even though the traffic is broadcast, it's safe to assume that encryption makes eavesdropping a waste of time. But since cellular technologies are not the cheapest, the solution fails to meet the requirement that it be as cheap as possible. Thus the answer is b, yet again, since the required result and one of the optional desired results is met.

 

  1. (10 points) On an Ethernet coaxial network, all users share the medium. Bob has just moved to your group (and network) from manufacturing, and he brought his ancient 80286 10MHz PC/AT with him. Bob’s system includes an equally decrepit NE 1000 Ethernet NIC. Knowing the overall performance of the network will be influenced by the speed of Bob’s computer, which of the following solutions makes the most sense, assuming you can’t replace his PC with a newer, faster model? Justify your choice.
    1. Replace the 8-bit NE 1000 with a 16-bit NE 2000.
    2. Replace the 8-bit NE 1000 with a 32-bit NE 3200 EISA card because EISA is backward-compatible with ISA, and you can enjoy the extra performance boost.
    3. Run a dedicated cable from the server to Bob’s machine and put him on his own network segment. That way, his laggard performance won’t affect anybody else.
    4. Buy a 32-bit PCI bus-mastering card and get Bob’s machine moving on the network as fast as possible.

Answer: A (5 pts) or C (3 pts). The real issue with Bob's PC is that it is painfully slow. This will affect the network only when he's transmitting data, however. Therefore replacing his NE1000 with an NE2000 is probably the most practical solution (answer a). Replacing the card with an EISA version does no good because an EISA card won't work in an ISA slot (although ISA cards can work in EISA slots, it doesn't work the other way around). If Bob generates a lot of traffic on the network, however slowly, answer c. will indeed isolate other users from his influence; in that case, this answer makes the most sense. Since you can't replace Bob's old PC with a new one, a PCI card won't work in his machine, either, so answer d. is completely incorrect. A is more practical than C.

 

  1. (10 points) You’ve just bought a fully featured new Pentium MMX PC. When you bring the machine into your test lab, you discover that all the interrupts your PCI Ethernet card can use (IRQ3, IRQ5, IRQ10, IRQ11, and IRQ15) are already taken by other devices, but IRQs 12 and 7 are available. Which of the following strategies is the most likely to produce a machine with a working network connection that preserves as much of the existing hardware as possible? Explain your answer in full.
    1. Read the manuals for the other adapters in the machine. If any of them use one of the IRQs the NIC needs and you can switch them to one of the open IRQs, your problem is solved.
    2. Remove all nonessential adapters and install the NIC. Then use whatever IRQs are available to install as many of the other adapters as you get working.
    3. Buy a PC card interface for your computer’s expansion chassis. Use a PC card NIC instead of the PCI Ethernet card you originally planned to use.
    4. Buy a serial-attached network interface. This will allow you to plug the network into your serial port and not have to change any of your other configurations. Who cares if the top speed of your serial port is 115Kbps?

Answer: A. Dealing with interrupt conflicts gets to be a way of life when installing NICs, especially for heavily-loaded end user machines. The only real solution to the problem that doesn't diminish the machine's current capabilities is to follow the strategy outline in answer a, and try to change the IRQ for some other device, to free up an IRQ that the NIC can use. Answer b implies that whatever devices can't be made to work can be omitted, which the user may not appreciate. Answer c may work, but the PC Card NIC will still need an IRQ, too—you may be spending more money, just to wind up with the same problem you were trying to solve. Answer d. limits the speed of the network attachment to serial port speeds; unless you spend real money ($150 or more) for a high-speed serial interface, you'll wind up with a network attachment that runs significantly slower than a NIC attachment. This is a solution that's only worth considering if all other options have been exhausted and the machine still can't be connected to the network.