Some networks connect to each other through the Internet, while others are private. For instance, the example addresses used in this course are private, which means that they are not assigned to publiè use. Both public and private IP addresses are required for both of these network types.
Public IP Addresses
Internet stability depends directly on the uniqueness of publicly used network addresses. Therefore, some mechanism is needed to ensure that addresses are, in fact, unique. This responsibility originally rested within an organization known as the InterNIC (Internet Network Information Center). The lANA succeeded the InterNIC. lANA carefully manages the remaining supply of IP addresses to ensure that duplication of publicly used addresses does not occur. Such duplication would cause instability in the Internet and compromise its capability to deliver datagrams to networks using the duplicated addresses.
To obtain an IP address or block of addresses, you must contact an Internet service provider (ISP). The ISP will then contact their upstream registry or their appropriate regional registry at one of these organizations:
• APNIC (Asia Pacific Network Information Center)
• AR1N (American Registry for Internet Numbers)
• RIPE NCC (Réseaux IP Européens Network Coordination Centre)
With the rapid growth of the Internet, public IP addresses began to run out, so new addressing schemes such as Network Address Translation (NAT), classless interdomain routing (CIDR), and IPv6 were developed to help solve the problem.