Homework 1 - Chapters 1 and 2

Due: Wednesday April 6, 2011 at 5:30pm

Answer the following questions. Each question is worth 2 points.

  1. Give two motivations for using a protocol stack.
  2. Consider a system with a 6 layer protocol stack. Layers 2 through 5 each add a 10 byte header. Layer 2 also adds a 4 byte footer. If a 52 byte message is generated at layer 6, what percentage of the bits transmitted over the physical media are overhead (headers and footers)?
  3. If the unit exchanged at the data link level is called a frame and the unit exchanged at the network level is called a packet, do frames encapsulate packets or do packets encapsulate frames?
  4. Describe the differences between a byte stream and an unacknowledged datagram.
  5. List two advantages to having standardized protocols.
  6. Assume there is no noise on a voice-grade telephone line and the data is transmitted using 2 discrete signal levels. What is the maximum data rate if the channel is sampled every 1 msec?
  7. If the signal-to-noise ratio is 20dB, what is the maximum data rate on a standard voice-grade telephone line?
  8. One method of transmitting data is to use portable media transported from one point to another. Consider a box of tapes. The box contains 20 tapes and each tape can hold 800GB of data. The tapes are transported by courier at 65mph. At what distance does the data transfer rate of this method become equivalent to setting up a dedicated OC-12 link (601.344 Mbps) between the two points.
  9. List two ways that fiber optic cables differ from coax cables.
  10. Does 802.11 use regulated or unregulated frequency bands?
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