IPv6 is internet protocol version 6. It is the next generation internet protocol. It is designed to be a successor of IPv4 or internet protocol version 4, whose first implementation is the internet and still is dominantly used. IPv6 has a very large address-space compared to traditional IPv4 protocol. IPv4 uses 128 bit address, but whereas IPv4 uses only 32 bit address. This expansion increases the flexibility for allocating addresses and also eliminates the use of network address translator more formally called as NAT. IPv4 is capable of having 2^32 that is 4 billion addresses. But the available space in IPv4 will last for only 2 or 3 decades due to the alarming growth of the internet. Ipv6 supports 2^128 address spaces. It has a 64 bit subnet and it can have 2^64 subnet addresses. When a host connects to an IPv6 network, the host sends a multicast router request for its parameters. If the configurations are suitable, the router responds to it by sending an advertisement packet that contains the configurations of the network layer. One of the base specifications in IPv6 is multicasting, whereas in IPv4 it’s optional. While upgrading to IPv6 from IPv4 the transport layers and the network layers do not need any change or they require only small changes.