Mi lett az IPv1, IPv2, IPv3 és IPv5-tel?

Itt írnak róla angolul: [link]

1.7 – Whatever Happened to IPv5?

Two of the common questions people ask when they start reading about IPv6 is “If it’s the next version

after IPv4, why isn’t it called IPv5?” and “What happened to the first three versions of IP?”

There is a four bit field in every IP packet header that contains the IP version number in binary. In IPv4,

that field contains the binary value 0100 (4 in decimal) in every packet. An earlier protocol (defined in

RFC 1190, “Experimental Internet Stream Protocol, Version 2 (ST-II)”, October 1990) used the binary

pattern 0101 (5 in decimal) in the IP version field of the packet header. The Internet Stream Protocol

was not really a replacement for IPv4, and isn’t even used today, but unfortunately the binary pattern

0101 was allocated to it. The next available bit pattern was 0110 binary (6 in decimal). It would be even

more embarrassing than explaining that there was no IPv5, to explain why the IP Version Number field

for IPv5 contained the value 6. Now you know.21

So what did happen to IPv1, IPv2 and IPv3? Well, TCP went through three versions (including all the

functionality of IP) before IP was split out into a separate protocol in RFC 791. So, IP began its

independent existence at version 4 (kind of like Windows NT starting life at version 3.1).

No protocols called IPv1, IPv2, IPv3 or IPv5 ever existed. IPv4 was the first release of the Internet

Protocol (1G Internet), and IPv6 is the second release (2G Internet). Hence my name for the Internet

based on it: the Second Internet.

There have been rumors about an IPv9 protocol in China. A Venture Capital firm in Hong Kong actually

asked me if China was already that far ahead of the rest of the world, and shouldn’t we be supporting

their version? It seems some researcher in a university there published a paper on an “IPv9”, but it was

never implemented, and wasn’t a replacement for IPv4 (let alone IPv6) anyway. It was a way to use 10

digit decimal phone numbers in a modified DNS implementation instead of alphanumeric domain

names, for all nodes on the Internet. I guess if you speak only Chinese, a 10 digit numeric string may

seem easier to use than an English domain name using Latin characters. Fortunately for Chinese

speakers, we will soon have Internationalized Domain Names in Chinese and other languages.

Actually, there is a real RFC about IPv9, which you might enjoy reading. See RFC 1606, “A Historical

Perspective On The Usage of IP Version 9”, April 1, 1994. This has nothing to do with the Chinese IPv9,

and is much funnier. This RFC is a network engineer’s equivalent to an integrated circuit data sheet I

once saw, concerning a logic gate (circuit) called a “maybe gate”. This gate is similar to “or gates”, “and

gates” and “nand gates”. There were two inputs to the maybe gate, each of which could be logic 0 or

logic 1. The output was “maybe 1, maybe 0”, it all depended on how the gate felt right then. Please

notice the release date of RFC 1606.