What is the differences between Internet Protocol Version IPv4 and IPv6 ?

Internet Protocol Version IPv6 is a newer version of Internet Protocol Version IPv4. In IPv6 significant changes has been created to overcome the Internet  Protocol Version IPv4 limitations. In IPv4 limitations include the following :

Limited address space: IPv4 uses only 32-bits to represent addresses. IANA has allocated the majority of these addresses.

Difficult routing management: IANA has not provisioned allocated IPv4 addresses for efficient route management. As a result, Internet backbone routers have over 85,000 routes in their routing tables.

Complex host configuration: Automatic configuration of IPv4 hosts requires that you implement DHCP.

No built-in security: IPv4 does not include any method for securing network data. You must implement Internet Protocol Security (IPSec) and other protocols to secure data on IPv4 networks, but this requires significant configuration and can be complex to implement.

Limited Quality of Service (QoS): The implementation of QoS in IPv4 relies on the use of TCP and User Datagram Protocol (UDP) ports to identify data. This may not be appropriate in all circumstances.

IPv6 improvements

IPv6 enhancements help enable secure communication on the Internet and over corporate networks. Some IPv6 features include the following:

Larger address space: IPv6 uses a 128-bit address space, which provides significantly more addresses than IPv4.

More efficient routing: IANA provisions global addresses for the Internet to support hierarchical routing. This reduces how many routes that Internet backbone routers must process and improves routing efficiency.

Simpler host configuration: IPv6 supports dynamic client configuration by using DHCPv6. IPv6 also enables routers to configure hosts dynamically.

Built-in security: IPv6 includes native IPSec support. This ensures that all hosts encrypt data in transit.

Better prioritized delivery support: IPv6 includes a Flow Label in the packet header to provide prioritized delivery support. This designates the communication between computers with a priority level, rather than relying on port numbers that applications use. It also assigns a priority to the packets in which IPSec encrypts the data.

Redesigned header: The design of the header for IPv6 packets is more efficient in processing and extensibility. IPv6 moves nonessential and optional fields to extension headers for more efficient processing. Extension headers are no more than the full size of the IPv6 packet, which accommodates more information than possible in the 40 bytes that the IPv4 packet header allocates.