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As all of us know that after IPv4 it came IPv6. How this transition happened?

I just want to know was there any IPv5 also? or there is any other logic in naming this version of IP as IPv6?

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I used to think IPv6 would support six address spaces instead of four like in IPv4. Turns out they multiplied it by 4 instead. –  Joe Z. Jan 31 '13 at 14:14
@EvanPlaice: After NCP, there was TCP, which had a version 1 and version 2. When it became clear the protocol needed to be split, version 3 became IPv3 and TCPv3. Both were declared stable at v4, and are protocols are what you're familiar with today. Because TCPv4 doesn't have to be run across IPv4, that protocol remains the same and IP has gone on to v6. –  Blrfl Feb 2 '13 at 0:39
In the olden days odd numbers usually represented beta releases (like the Internet streaming protocol was) –  Sylwester Jun 9 '13 at 23:12
IP versions 7, 8 and 9 were also assigned to potential IPv4 replacements, so if anything comes after IPv6 it will begin with IPv10. –  Michael Hampton Jul 30 '13 at 4:26
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4 Answers

up vote 55 down vote accepted

According to Wikipedia, Internet Protocol Version 5 was used by the Internet Stream Protocol, an experimental streaming protocol.

The second version (of Internet Stream Protocol), known variously as ST-II or ST2, distinguishes its own packets with an Internet Protocol version number 5, although it was never known as IPv5.

The Internet Stream Protocol family was never introduced for public use, but many of the concepts available in ST are similar to later Asynchronous Transfer Mode protocols and can be found in Multiprotocol Label Switching (MPLS). They also presaged Voice over IP.

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"So what happened to IPv5? IPv5 was used to define an experimental real-time streaming protocol. To avoid any confusion, it was decided to not use IPv5 and name the new IP protocol IPv6. " (Cisco CCNA Exploration Courses - Accessing the WAN)

Here's a link! @ Hemant You will find there enhancements that IPv6 offers.

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Nice quote. Could you add a link to it? That would really help this answer. –  Mason Wheeler Feb 1 '13 at 23:17
@lucian oprea : thanks for link :) –  Hemant Feb 3 '13 at 8:55
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In the late 1970’s, a protocol named ST — The Internet Stream Protocol — was created for the experimental transmission of voice, video, and distributed simulation. Two decades later, this protocol was revised to become ST2 and started to get implemented into commercial projects by groups like IBM, NeXT, Apple, and Sun. Wow did it differ a lot. ST and ST+ offered connections, instead of its connection-less IPv4 counterpart. It also guaranteed QoS. ST and ST+, were already given that magical “5″.


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What website did you steal this material from? Oh Right...oreillynet.com/onlamp/blog/2003/06/… –  Ramhound Jul 10 '13 at 12:07
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IPv5 was used to define an experimental real-time streaming protocol. To avoid any confusion, it was decided to not use IPv5 and name the new IP protocol IPv6. Another thing is that IPv6 has a high span of IP adresses that is up to 340 trillion trillion trillions.

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