What is THE IP‑ADDRESS

THE IP‑ADDRESS

An IP address is a numerical address that is assigned to every device connected to the Internet. 01
In many cases, IP addresses may be used to identify an organisation or individual that has acquired the services of an Internet Service Provider in order to connect one or more devices to the Internet.
In other cases, particularly on corporate networks, public
 or unprotected wireless connections and mobile Internet connections,
the IP address does not always identify the person behind
some digitally traceable act.
As the common household and business router will o                            
ften display just one IP address for all of the people                
connected to it, the IP address will identify a group                                      
of people rather than just one individual. As a result,
 it is often hard, if not impossible, to be sure who exactly did what,
purely on the basis of an IP address.
On the other hand, IP addresses are very often
 personally identifiable, and so, following a basic
 precautionary principle, must be treated as such u
nless they can definitively proven not to be.

                     “the IP address does not always identify t

he person behind some

 digitally traceable act”

Significance of IP networks and hosts

• • An IP host is any device with an IP address, such as a PC.
• • Multiple hosts reside on a given IP network or subnet (short for
• subnetwork). Subnets will be discussed later.
• • A group of IP networks is an internetwork, with the largest internetwork
• being the Internet.
• • What is typically called a “data network” is technically an internetwork,
• because multiple IP networks are connected together by routers.
• • This internetwork contains 6 IP networks.
• • Note that even a link between routers is a network.

Public addresses

• • Most IP addresses are public addresses. Public addresses are registered
• as belonging to a specific organization.
• • Internet Service Providers (ISP) and extremely large organizations in the
• U.S. obtain blocks of public addresses from the American Registry for
• Internet Numbers (ARIN http://www.arin.net). Other organizations obtain
• public addresses from their ISPs.
• • There are ARIN counterparts in other parts of the world, and all of these
• regional registration authorities are subject to the global Internet Assigned
• Numbers Authority (IANA http://www.iana.org).
• • Public IP addresses are routed across the Internet, so that hosts with
• public addresses may freely communicate with one another globally.
• • No organization is permitted use public addresses that are not registered
• with that organization!