Page 252 -

Use of Private IP Addresses Q6-3 How Does the Cloud Work? 251
When your computer accesses a public site, say, www.pearsonhighered.com, from within a LAN at,
say, a coffee shop, your traffic uses your private IP address until it gets to the LAN device. At that
point, the LAN device substitutes your private IP address with its public IP address and sends your
traffic out onto the public Internet.
This private/public IP address scheme has two major benefits. First, public IP addresses are
conserved. All of the computers on the LAN use only one public IP address. Second, by using private
IP addresses, you are protected from attackers directly attacking you because they cannot send attack
packets to private IP addresses. They can only send packets to devices with public IP addresses.

Public IP Addresses and Domain Names

IP addresses have two formats. The most common form, called IPv4, has a four-decimal dotted
notation such as 165.193.123.253; the second, called IPv6, has a longer format and will not
concern us here. In your browser, if you enter http://165.193.140.14, your browser will connect
with the device on the public Internet that has been assigned to this address.
Nobody wants to type IP addresses such as http://165.193.140.14 to find a particular site.
Instead, we want to enter names such as www.pandora.com or www.woot.com or www. pearsonhighered.
com. To facilitate that desire, ICANN administers a system for assigning names to IP addresses. First,
a domain name is a worldwide-unique name that is affiliated with a public IP address. When an
organization or individual wants to register a domain name, it goes to a company that applies to an
ICANN-approved agency to do so. GoDaddy (www.godaddy.com) is an example of such a company
(Figure 6-8).
GoDaddy or a similar agency, will first determine if the desired name is unique worldwide. If
so, then it will apply to register that name to the applicant. Once the registration is completed, the
applicant can affiliate a public IP address with the domain name. From that point onward, traffic
for the new domain name will be routed to the affiliated IP address.
Note two important points: First, several (or many) domain names can point to the same IP
address. Second, the affiliation of domain names with IP addresses is dynamic. The owner of the
domain name can change the affiliated IP addresses at its discretion.
In 2014, the U.S. Department of Commerce announced it was giving up oversight over
ICANN. Critics worry that less-free countries will now try to force ICANN to disallow domain
names for dissident groups, thereby kicking them off the Internet. At this point, it’s still unclear
how ICANN will be governed.

Figure 6-8
GoDaddy Screenshot
Source: © 2015 GoDaddy Operating
Company, LLC. All rights reserved.