5A. On September 11, 2001, terrorists
commandeered and crashed two civil airliners into the main towers of the World
Trade Center in New York City. The resulting fires caused the two towers to
collapse and damaged nearby buildings including the Wall Street Journal's main
editorial offices at 200 Liberty Street. A typical national newspaper's
editorial office are linked both to newspaper correspondents worldwide providing
editorial content and also to multiple sites for printing and delivery
throughout the United States. For several days, following the terrorist attack,
the Journal's Online Edition was not published. Service was restored only later
in the week.
a) Compare the Journal's two networks -- editorial and distribution -- in terms of the uplink/downlink symmetry of data traffic. Given these traffic patterns, which transmission media would you choose for the two networks? Justify your answer.
b) Evidently, the database architecture of the Journal's editorial system was centralized. Suggest two ways by which the impact of the World Trade Centre attack on the Journal's service could have been reduced.
c) Compare your two suggestions in terms of cost-effectiveness. Are they related to your choice of transmission media in part (a)?
5B. The available capacity for international communications by both undersea cable and satellite is continuously increasing. The proportion, however, of capacity over undersea cables is increasing relative to satellite capacity.
a) What are the reasons for this trend?
b)
Consider a carrier that has
both satellite and cable circuits. What types of traffic should it channel by
satellite, and what types by cable?
c) SOC Bank has contracted with a global service provider for a network of high-speed fiber optic circuits for data communications among its offices in major international financial centers. The network manager is concerned about maintaining communications in the event of natural disasters. In what way could he address this problem? Explain your answer.