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Q3 How Does the Cloud Work? 217
Cable Line

A cable line is the second type of WAN connection. Cable lines provide high-speed data trans-
mission using cable television lines. The cable company installs a fast, high-capacity optical fi-
ber cable to a distribution center in each neighborhood that it serves. At the distribution center,
the optical fiber cable connects to regular cable-television cables that run to subscribers’ homes
or businesses. Cable signals do not interfere with TV signals.
Because as many as 500 user sites can share these facilities, performance varies depending
on how many other users are sending and receiving data. At the maximum, users can download
data up to 50 Mbps and can upload data at 512 Kbps. Typically, performance is much lower than
this. In most cases, the download speed of cable lines and DSL lines is about the same. Cable
lines use their own protocols.
WAN Wireless Connection

A third way that you can connect your computer, mobile device, or other communicating device
is via a WAN wireless connection. Amazon.com’s Kindle, for example, uses a Sprint wireless
network to provide wireless data connections. The iPhone uses a LAN-based wireless network if
one is available and a WAN wireless network if not. The LAN-based network is preferred because
performance is considerably higher. As of 2013, WAN wireless provides average performance of
500 Kbps, with peaks of up to 1.7 Mbps, as opposed to the typical 50 Mbps for LAN wireless.

Q3 How Does the Cloud Work?

Jason and Kelly are flabbergasted at the low cost of the cloud. They doubt that it’s real. They
would be less cautious if they understood how the cloud operates. This section will give you the
basic understanding that they lack and enable you to be an effective consumer of cloud services.
The cloud resides in the Internet. So, in order to learn how the cloud works, you need a basic
understanding of how the Internet works. With that background, you will learn how it is possible
for a cloud vendor to provide dramatic elasticity to support the workload shown in Figure 6-1.
The technology that underlies the Internet and the additional technology that enables the
cloud to work are complicated. Here we will stay at a high level and help you learn overarching
concepts and basic definitions. We begin with a simple example.

An Internet Example

Figure 6-7 illustrates one use of the Internet. Suppose that you are sitting in snowbound
Minneapolis, and you want to communicate with a hotel in sunny, tropical northern New
Zealand. Maybe you are making a reservation using the hotel’s Web site, or maybe you are send-
ing an email to a reservations clerk inquiring about facilities or services.
To begin, note that this example is an internet because it is a network of networks. It con-
sists of two LANs (yours and the hotel’s) and four networks. (In truth, the real Internet consists
of tens of thousands of networks, but to conserve paper, we don’t show all of them.) A hop is the
movement from one network to another. As drawn, in Figure 6-7, the shortest path from you to
the hotel’s LAN consists of four hops. This term is frequently used by cloud vendors when they
discuss provisioning servers to minimize the number of hops.

Carriers and Net Neutrality

As your message, or packet, moves across the Internet, it passes through networks owned by
large telecommunication providers known as carriers. Some of these large carriers include
Sprint, AT&T, Verizon Business, and XO Communications. These large carriers exchange traffic
freely without charging each other access fees via peering agreements. Carriers make revenue
by collecting subscription fees from end users, but not from peers.