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The IPv4/IPv6 Basics
The address space is the main difference between IPv4 (32-bit) and IPv6 (64-bit). The text representation has also been changed from a 2-digit partitioning for IPv4 to 4-digits for IPv6. An IPv4 example address is 12:34:56:78. An IPv6 example address is 1234:5678:9abc:def0:1234:5678:9abc:def0. The IPv6 representation also allows double colons (::) to represent a string of zero entries so 1234:0:9abc:0:0:0:0:def0 could be 1234:0:9abc::def0.
Packets for both IPv4 and IPv6 are variable and they can be up to 64 Kbytes. The problem is that the protocols can be used over a number transports that may have other limits. This is normally specified by the maximum transmission unit (MTU). Both protocols have a minimum MTU requirement. This is 576 bytes for IPv4 and 1280 bytes for IPv6.
Larger data payloads can be shipped around the network by breaking the data among multiple packet fragments. This is typically done by the host but in IPv4 this can also be done by routers. IPv6 hosts need to determine the MTU for a path to a destination. This approach simplifies routers but adds complexity at the host end. This is normally not an issue and the IPv6 minimum MTU can always be used with any path.
The other big difference between IPv4 and IPv6 is the header. There are changes in the number and type of fields and extensions are handled in a different fashion. The IPv6 header is always 40 bytes and can be followed by any number of extension headers and then the data. This approach is more flexible but harder to process since the number and size of additional headers is variable.
IPv6 is the 6th amendment to the Web Convention and the successor to IPv4. It works also to IPv4 in that it gives the extraordinary, numerical IP addresses important for Web empowered gadgets to impart. Be that as it may, it sports one noteworthy contrast: it uses 128-piece addresses.
