The IT Stuff

Comapre IPV4 and IPV6
IPV4

Source and destination addresses are 32 bits (4 bytes) in length.
Over 109; possible addresses
IPSec support is optional.
Represented by dotted decimal notation
Packet Header is of variable size  this is  time consuming to handle
No identification of packet flow for QoS handling by routers is present within the IPv4 header.
Fragmentation is performed by the sending [...]

Compare IPv6 header VS. IPv4 header

Move from or Compare IPv4 to IPv6
Address
IPv4

32 bit long(4bytes)
Address= Network+Host
Network and Host portion depends on classes
Classes for identification depends upon the initial bits
Total no of IPv4 addresses are 4,294,967
Represented by dotted decimal or binary (192.168.100.1)

IPv6

128 bit long(16bytes)
Basic architecture = (64 bits) network + (64 bits) host .
Host Portion often be the MAC address or interface [...]

Understand IPv6 Addresses
In IPv4 there were three type of addresses  unicast, broadcast and multicast addresses. In IPv6 we have unicast, multicast and anycast.
The broadcast addresses are not used anymore in IPv6, because they are replaced with multicast addressing.
IPv6 addresses  can be categorized by type and scope:

Unicast addresses. A packet is delivered to one [...]

What is IPv6 and Features as Compare to IPv4?
IPv6 is short for “Internet Protocol Version 6″. IPv6 is the “next generation” protocol designed by the Internet Engineering Task Force (IETF) to replace the current version Internet Protocol, IP Version 4 (“IPv4″).
Most of today’s internet uses IPv4, which is now nearly [...]