The features of IPv6 are listed below.
• New Packet Format and Header: IPv6 specifies a new packet format. The new IPv6 packet format helps to minimize packet header processing by routers. This is achieved by moving both nonessential and optional fields to extension headers that are placed after the IPv6 header. Since IPv4 packets and IPv6 packets are significantly different, the two protocols are not interoperable.
• Large Address Space: IPv4 has 32 bit (4-byte) address space, but IPv6 has 128-bit (16-byte) address space. The very large IPv6 address space supports a total of 2128 (3.4×1038) addresses. This large address space allow a better, systematic, hierarchical allocation of addresses and efficient route aggregation. With the large number of available addresses we can eliminate address-conservation techniques like NAT (Network Address Translation).
• Statefull and Stateless IPv6 address configuration: In IPv6 statefull or stateless configuration is possible. Hosts on a link can automatically configure with IPv6 addresses called link-local addresses and with addresses derived from prefixes advertised by local routers. When first connected to a network, a host sends a link-local router solicitation multicast request for its configuration parameters. The router which is available in the link responds to the request from the host with a router advertisement packet that contains network-layer configuration parameters. Hosts can configure link-local addresses automatically and communicate each other without manual configuration even there is no router available. The hosts may also have stateful configuration with the Dynamic Host Configuration Protocol version 6 (DHCPv6) or static configurations, as IPv4.
• Multicast: The three types of communication available in in IPv4 are unicast, multicast and broadcast. Unicast is one-to-one communication; multicast is one-to-many communication and broadcast is one-to-all communication. The transmission of a packet to all hosts was performed by using special broadcast addresses in IPv4. Broadcast communication is not available in IPv6 and therefore does not define broadcast addresses. In IPv6, the effect of broadcast can be achieved by sending a packet to the link-local all nodes multicast group at address ff02::1.
• Integrated Internet Protocol Security (IPSec): Internet Protocol Security (IPSec) is a set of Internet standards that uses cryptographic security services to provide Confidentiality, Authentication, Data integrity. The support for Internet Protocol Security (IPSec) was optional in IPv4. Internet Protocol Security (IPSec) is an integral part of the base protocol suite in IPv6. Internet Protocol Security (IPSec) support is mandatory in IPv6.
• Neighbor Discovery Protocol: The Neighbor Discovery Protocol (NDP) is a protocol available IPv6. The Neighbor Discovery protocol (NDP) is based on Internet Control Message Protocol Version 6 (ICMPv6) messages that manage the interaction nodes on the same link. There is no Address Resolution Protocol (ARP) for IPv6 and the role of the Address Resolution Protocol (ARP) is replaced by Neighbor Discovery Protocol (NDP).
• Extensibility: The features of IPv6 can be extended by adding extension headers after IPv6 header. The size IPv6 extension headers is constrained only by the size of the IPv6 datagram packet, unlike 40 bytes of options of IPv4.
• Jumbograms: Jumbograms is an optional feature of IPv6. Jumbograms allow packets with payloads 2^32 - 1 (4,294,967,295) bytes by making use of a 32-bit length field.