ok, i know, this time i'll be banned with ip banned :D my question is quite strange: why only the V4 and then jumped to V6 are adopted! why when hearing about internet history we dont find IP V3 or IP V2?! why they dident Just adopt the IP V5, this was logic no?
because personnaly (am dumb) i thought that 4 and 6 were the number of bytes used...
The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5
http://en.wikipedia.org/wiki/IP_address#IP_versions
IPv1, 2, & 3 would actually be part of the TCP/IP protocols, of which there were 3 versions. IPv4 is were they split the 2 in to separate protocols and created an updated IP protocol.
http://itknowledgeexchange.techtarget.com/itanswers/what-happened-to-ipv1-ipv2-ipv3-and-ipv5/
Charles M. Kozierok, author of tcpipguide.com, nicely explains why first version of IP is version 4 (not version 1):
[Jon] Postel's observation led to the creation of TCP/IP architecture, and the splitting of TCP into TCP at the transport layer and IP at the network layer; thus the name “TCP/IP”. (...) The process of dividing TCP into two portions began in version 3 of TCP, written in 1978. The first formal standard for the versions of IP and TCP used in modern networks (version 4) were created in 1980. This is why the first “real” version of IP is version 4 and not version 1. (...)
IPv4 was introduced by Jon Postel in RFC760 and later updated by RFC777 (introducing ICMP) and replaced by RFC791.
Both RFC777 and RFC791 were later updated many times, which you can clearly see if you generate RFCs graph. Simplified RFCs graph is also available here. Since finding RFC760 on this site is quite difficult, here you have helpful screenshot.
Number 5 in IP's header means that it's Internet Stream Protocol datagram. Internet Stream Protocol (ST and later ST2) was proposed in 1979 in IEN119 and later described in RFC1190 and RFC1819.
Page 64:
Protocol is 5 to indicate an ST packet is enclosed, as opposed to TCP or UDP, for example. The assignment of protocol 5 to ST is an arranged coincidence with the assignment of IP Version 5 to ST [18]
Page 75:
IP currently uses a value of 4, while ST has been assigned the value 5 [18]. There is no requirement for compatibility between IP and ST packet headers beyond the first four bits.
Page 8:
Both ST2 and IP apply the same addressing schemes to identify different hosts. ST2 and IP packets differ in the first four bits, which contain the internetwork protocol version number: number 5 is reserved for ST2 (IP itself has version number 4). As a network layer protocol, like IP, ST2 operates independently of its underlying subnets. Existing implementations use ARP for address resolution, and use the same Layer 2 SAPs as IP.
As a special function, ST2 messages can be encapsulated in IP packets. (...)
Page 77:
IP and ST packets can be distinguished by the IP Version Number field, i.e., the first four (4) bits of the packet; ST has been assigned the value 5 (see [RFC1700]). There is no requirement for compatibility between IP and ST packet headers beyond the first four bits. (IP uses value 4.)
I think the primary issue is hardware acceleration. The big warehouses and internet controllers have hardware-accelerated v4/v6 routers. They don't want to replace this stuff more than once in 20 years. It's too expensive to do it more than that.
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