During the design of most real-world networks, you will discover that using more than one type of networking medium is common. The usual reasons for needing more than one type of medium include the following:

• Two or more areas must be interconnected, and the distance separating them is greater than the maximum segment length for the type of medium used in (or best suited for) each area.

• A connection must pass through a high-interference environment (across some large transformers, near heavy-duty electrical motors, and so on). Failure to use a different type of medium increases the risk of impeding data flow. This reason is especially common for choosing fiber-optic cable or wireless in many networks, particularly when connecting floors in an office building and the only available pathway is the elevator shaft.

• Certain parts of an internetwork might have to carry more traffic than other parts. Typically, the segment where traffic aggregates is the backbone, a common cable segment that interconnects subsidiary networks (think of a tree trunk as the backbone and its major branches as cable segments). Often, a higher-capacity cable is used for a backbone (for example, fiber-optic cable or Cat 6 cable rated for Gigabit Ethernet), along with a higher-speed networking technology for attachments to the backbone. This arrangement means outlying segments might use conventional 10 or 100 Mbps Ethernet, and the backbone uses 1 Gbps or 10 Gbps Ethernet.

Using this information, suggest solutions that involve at least two types, if possible, of networking media to address the following problems:

1. XYZ Corp. is planning a new network. Engineers in the design shop must have connections to accountants and salespeople in the front office, but all routes between the two areas must traverse the shop floor, where arc welders and metal-stamping equipment create potent amounts of EMI and RFI. Given that both the design shop and front office use 10BaseT (twisted-pair Ethernet), how might you interconnect these two areas? What medium guarantees immunity from interference?

2. After the front-office network at XYZ Corp. is set up, an accountant realizes that if the loading dock connected to the network, dock workers could log incoming and outgoing shipments and keep the inventory more current. Even though the loading dock is nowhere near the shop floor, the dock is 1100 feet from the front office. What kinds of cable will work to make this connection? What kind would you choose and why?

3. ABC Company occupies three floors in a 10-story building, where the elevator shaft provides the only path to all three floors. In addition, users on the ninth and tenth floors must access a collection of servers on the eighth floor. Explain what kind of connections would work in the elevator shaft. If more than once choice is possible, pick the best option and explain the reasons for your choice. Assuming that interfloor connections might someday need to run at much higher speeds, reevaluate your choice. What's the best type of medium for open-ended bandwidth needs? Explain your answer.

4. Very Big ISP (VBISP) Corporation wants to increase the bandwidth it can access at its downtown location in New York City. The distance between locations is about 20 miles, and the bandwidth needed between locations is at least 50 Mbps. What media types could work to provide this connection?

5. Following a year of major sales increases in the Pacific Rim, MarTexCo decides to open a second plant in Malaysia. The company wants the new plant to be able to access the headquarters database in Des Moines, Iowa, in real time, but long-haul telephone connections are not possible, owing to the lack of communications infrastructure at the Malaysia location. What kind of wireless networking alternative makes the most sense when considering network links that span an appreciable portion of the globe? Explain why laying cable might not be feasible.