Internet Protocol versions IPv4, IPv5 and IPv6
By Stephen Bucaro
IPv4 (Internet Protocol version 4) is the part of the TCP/IP protocol that is responsible
for addressing packets, fragmenting and reassembling packets, specifying the type of
service, and security. IP by itself doesn't establish a connection between source and
destination. The TCP (Transmission Control Protocol) is what establishes and monitors
the connection between source and destination.
IPv4 uses a 32-bit address scheme which allows for a maximum of just over 4 billion
addresses. With all the devices connected to the Internet today, eventually all the
addresses will be used. The IETF (Internet Engineering Task Force) began working on IPv6
(Internet Protocol Version 6), a standard for a 128-bit IP address in 1998. IPv6 allows
for a maximum of about 340 trillion, trillion, trillion addresses. IPv6 (Internet Protocol
Version 6) is designed to work along side IPv4, and may someday replace IPv4.
Because 32-bit binary numbers are difficult for humans to read, IPv4 addresses are written
as four 8-bit values separated by dots. For example 184.108.40.206 could be an IPv4 address.
A 128-bit IPv6 binary number would be even more difficult for humans to read, so IPv6
addresses are written as eight 16-bit values expressed in hexadecimal notation separated
by colons. For example 8f:fe21:3ffe:67cf:1900:4545:f8:200 could be an IPv6 address.
What happens when all the IPv4 addresses are used up? Nothing, because IPv6 is designed
to work along side IPv4. A process has been designed that will automatically convert
IPv4 addresses to IPv6 addresses. The conversion involves using a process called EUI-64
(Extended Unique Identifier) to expand a devices 48-bit MAC address to 64 bits (basically
by inserting FFFE between the OUI part and the NIC specific part), then prefixing the
32-bit IPv4 address with a 16-bit IPv6 header and a 16-bit code to identify that the
address is an IPv4 to IPv6 converted address.
As far as enterprise networks are concerned, using the conversion process described
above, IPv4 networks are expected to operate along with IPv6 based networks for a long
time into the future. However, some old IPv4 based consumer devices may eventually stop working.
You may be wondering what happened to IPv5. An Internet protocol experimented with in
the 1980s used the version 5 designation, but it was never widely adapted.