PROBLEM SOLUTIONS 1 SOLUTIONS TO CHAPTER 1 PROBLEMS 1. Because the raven flies at an average speed of 40 km/h, it needs 160/40 = 4 hours for each one-way trip. (i) The raven makes only one trip because 1.8 terabytes exactly fits on one scroll. 1800 GB 4 h × 3600 = 1 8 GB/s = 1 Gbps (ii) To communicate 3.6 TB of data, the raven has to fly back to pick up a second scroll. This means that it needs to fly a total of 3 × 4 = 12 hours. 3600 GB 12 h × 3600 = 1 12 GB/s = 2 3 Gbps (iii) The receiving castle receives 1.8 terabytes of data every 8 hours. 1800 GB 8 h × 3600 = 1 16 GB/s = 1 2 Gbps 2. There are multiple correct answers. A significant disadvantage is the increased risk of invading people’s privacy. The increase in the number of networked devices means a larger attack surface for malicious parties trying to obtain personal information. If the information is not stolen, companies that process and store data from IoT devices could sell it to third parties such as advertising companies. 3. Secondly, wireless networks allow people to move around, instead of tying them to a wall. Secondly, although wireless networks provide lower bandwidth than wired networks, their bandwidth has become large enough to support applications that people find meaningful. Examples include media streaming and video conferencing. Finally, installing wires in (old) buildings can be expensive. 4. An advantage for the company is that they do not have to pay the up-front cost when buying expensive hardware. They lease machines from the data center, paying only for what they use. A disadvantage for the company is that they may not know the underlaying infrastructure used by the data center, making it more difficult to obtain high performance from their applications. The large amount of resources available in data centers makes it is easier for the company to scale with user demand, which is an advantage for both. A disadvantage for the users is that it becomes more difficult to track their own data, and what it is used for.