IPv6 versus IPv4

Internet Protocol version 6 (IPv6), also known as the Internet Protocol next generation (IPng) is intended to sustain constant Internet growth with consideration of the number of users and functionality. The legacy IP version, IPv4, was implemented in the early 1980's based on stationary wired communication infrastructure. The IPv4 supports less than 2³² (over 4 billion) individual addresses, hence IPv4 suffers some limitations that may be inhibitors to growth of "tomorrow's" Internet, and use of the Internet as a global networking solution. Therefore, IPv6 is under development to take over IPv4's position by providing a greater expansion of IP address space; nonetheless, incorporating features of such include end-to-end security, mobile communications, Quality of Service (QoS), and system management burden reduction.

Without adequate global IP address space, applications have to work in such ways to afford local addressing. In a short-term, there have been various discretionary "workarounds" and extensions to IPv4 in and attempt to overcome its limitations. Network Address Translation (NAT) enables multiple devices to utilize local private addresses within an enterprise at the same time sharing one or more global IPv4 addresses for external communications. While NAT, to a certain degree, has postponed the exhaustion on IPv4 address space for the time being, it also complicates common application bi-directional communication. IPv6 simplifies the confusion of presenting an end-to-end security and eliminates the general incentive for using NAT since global addresses will be extensively accessible.

IPv4 had numerous issues, one of which was not having sufficient geographical distribution; it currently has less than 50% coverage throughout the USA. One the other hand, routing was too complex for new technologies and features such as mobile computing had coverage areas issues. Most significantly, the number of IP addresses is reaching its limit and the time has come to adopt IPv6 to compensate for the technical and address space requirements. Figure 1 shows IPv4 and IPv6 header formats.

Figure 1: IPv6 versus IPv4 header

 

Table 1 shows the differences in the IPv4 and IPv6 headers fields' differences. As shown, IPv6 offers a few additional fields compared to IPv4.

Table 1: IPv6/IPv4 header field differences 

IPv4 Header field	IPv6 Header field
ToS	Traffic class filed (QoS parameter)
Total length	Payload length
TTL	The Next header
N/A	Flow label (QoS parameter)
N/A	Next Header
The source address and destination addresses are based on 32-bits address fields	The source address and destination addresses are based on 128-bits address fields