IPv6 is a layer 3 routing protocol and defines a header that holds both the source and destination address fields, just like IPv4. The IPv6 header is not similar to the IPv4 header and the differences are more than just bigger source and destination addresses. The IPv6 header is bigger in size compared with the IPv4 header, though it is otherwise simpler for the sake of reducing the computational overhead on routers that process IPv6 packets. The following diagram displays the IPv6 header: