Assignment 3

The assignment is due Thursday, November 3, 6.59 pm EDT, to be submitted via CourseWorks.

Some of the questions below are research questions, where you are asked to find information about a particular issue. You may use the Engineering Library, any text books you have, one of the paper from the class readings, or the web to come up with answers. Be sure to cite your sources. Generally, a paragraph or two should be sufficient to answer the question. There is no need to write a tutorial.

  1. Compute the theoretical storage capacity of a 60-minute cassette tape. Assume that such a tape recorder has a signal-to-noise ratio of 60 dB and a frequency range of 20 Hz to 20 kHz. (Early personal computers such as the TRS-80 and PET used cassette tapes for data storage.)
  2. Modulation: Binary Phase Shift Keying (BPSK) is commonly used as a low-complexity encoding. Using the Wikipedia definition, plot the waveform generated by BPSK with a symbol rate of 1 kb/s, Eb of 1 and a carrier frequency of 10 kHz. (Such a low carrier frequency is obviously unrealistic, but it makes the plot easier to read. However, standard IR remote controls use low frequency carriers of around 38 kHz and similar modulation.) Encode the sequence 101011.
  3. Wireless: In this problem, we'll investigate what it would take to replace DSL by LTE in urban areas. Assume that an average household of 2.59 and the population density is 1865. consumes 10 GB of data per month (20% upload and 80% download). The spectral efficiency of LTE is given in a presentation (slide 11). We assume that base stations are placed on a grid, one mile apart and use three sectors (120 degrees). How much spectrum would you need? Name at least one reason why this model is somewhat optimistic.
  4. Try connecting to 10 of the IPv6-capable web hosts and perform a traceroute. (Be sure that your system is configured to use IPv6; it should work on the Columbia University network.) Does the path length differ between IPv4 and IPv6?
  5. Addressing: What IPv4 address ranges are set aside for special purposes, other than global unicast host addresses? What fraction of the address is thus unavailable? In particular, consider the so-called 'class E' space. How long would it last if made available?
  6. IPv6: Extend the UDP/TCP client/server program from assignment 1 support IPv6, including AAAA records, using your experience from assignment 2. It is desirable, but not required, to support DNS lookups over IPv6. Hint: On Solaris and Linux systems, try man ipv6 to discover how to use IPv6 sockets, on MacOS man 4 ip6. See also the various Linux documents on this topic. As in the first assignment, include a packet trace (tcpdump).
  7. BGP: Using the figure below, show how the network prefixes A and B are exported via BGP, assuming the BGP relationships indicated by blue lines between the network clouds. In this network, how would packets from A get to B?