.: Advanced Linux Networking :.

The Internet is built on TCP/IP protocols, and particularly on version 4 of the IP protocols (IPv4). Unfortunately, IPv4 is showing its age in many ways. For instance, it supports IP addresses that are four bytes (32 bits) in length, meaning that there is a theoretical maximum of 232, or 4,294,967,296, addresses. Because of inefficiencies in the way addresses are assigned, the number of Internet addresses is actually much lower than this. Consequently, the Internet is running out of addresses. IPv4 also has security limitations that allow miscreants to seriously disrupt Internet operation. These problems are not severe in 2002, but they're likely to become critical well before decade's end.

For these reasons, an upgrade to IPv4, known as IPv6, is under development. Among other things, IPv6 uses a 128-bit IP address for a theoretical maximum of 2128, or 3.4 x 1038 addresses—enough for 2.2 x 1018 addresses per square millimeter of land surface on the Earth. IPv6 also includes better hooks for certain types of security systems than does IPv4. In 2002, few networks allow the use of IPv6, but if yours is one, or if you want to experiment with IPv6 on a private internal network, you can activate experimental Linux IPv6 support via the IPv6 Protocol (Experimental) option in the Networking Options menu. Once you do this, another option or two may become available, including an entire submenu entitled IPv6: Netfilter Configuration. This submenu includes a subset of options similar to those described earlier, in "Network Filter Options," but geared towards IPv6 rather than IPv4.