Internet Protocol version 6 (IPv6) is the latest revision of the Internet Protocol (IP) and the first version of the protocol to be widely deployed. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion.

Currently, the Internet and a number of private networks use the basic network infrastructure called Internet Protocol version 4, also known as IPv4. The IPv4 addresses are 32 bits long where four numbers from 0-255 are separated by periods.

IPv6 Addressing

The Internet Protocol version 6 (IPv6) is more advanced and has better features compared to IPv4.  It has the capability to provide an infinite number of addresses.  IPv6 has moved from a 32-bit address space to a 128-bit address space.  Therefore, the need for Classless Inter-Domain Routing (CIDR) is no longer needed because the number of addresses needed is no longer a concern.  The number of address available per person on this planet is approximately 1030.  The IPv6 addressing architecture makes a few adjustments to different types of address available to and IP host.

Types of IPv6 Address

There are three types of IPv6 addresses,

  1. Unicast – one-to-one communication. A single source is transmitting data to a single destination.
  2. Multicast– one-to-many communication. A transmission is received by a group of devices as the destination.
  3. Anycast– similar to multicast, however, the source chooses the closest destination of many for transmission.

The unicast and multicast addresses are similar to the IPv4 versions. However, the IPv4 broadcast address is no longer supported and is replaced with a new type of address called anycast.


IPv6 offers the following features:

  • Larger Address Space

In contrast to IPv4, IPv6 uses 4 times more bits to address a device on the Internet. This much of extra bits can provide approximately 3.4×1038 different combinations of addresses.

  • Simplified Header

IPv6’s header has been simplified by moving all unnecessary information and options (which are present in IPv4 header) to the end of the IPv6 header.

  • End-to-end Connectivity

Every system now has a unique IP address and can traverse through the Internet without using NAT or other translating components. After IPv6 is fully implemented, every host can directly reach other hosts on the Internet, with some limitations involved like Firewall, organization policies, etc.

  • Auto-configuration

IPv6 supports both stateful and stateless auto-configuration mode of its host devices. This way, the absence of a DHCP server does not put a halt on inter-segment communication.

  • Faster Forwarding/Routing

Simplified header puts all unnecessary information at the end of the header. The information contained in the first part of the header is adequate for a Router to make routing decisions, thus making routing decision as quickly as looking at the mandatory header.

  • IPSec

Initially, it was decided that IPv6 must have IPSec security, making it more secure than IPv4. This feature has now been made optional.

  • No Broadcast

Though Ethernet/Token Ring is considered as a broadcast network because they support Broadcasting, IPv6 does not have any broadcast support any more. It uses multicast to communicate with multiple hosts.

  • Anycast Support

This is another characteristic of IPv6. IPv6 has introduced Anycast mode of packet routing. In this mode, multiple interfaces over the Internet are assigned same Anycast IP address. Routers, while routing, send the packet to the nearest destination.

  • Mobility

IPv6 was designed keeping mobility in mind. This feature enables hosts (such as a mobile phone) to roam around in the different geographical area and remain connected with the same IP address.

  • Enhanced Priority Support

IPv4 used 6 bits DSCP (Differential Service Code Point) and 2 bits ECN (Explicit Congestion Notification) to provide Quality of Service but it could only be used if the end-to-end devices support it, that is, the source and destination device and underlying network must support it.

In IPv6, Traffic class and Flow label are used to tell the underlying routers how to efficiently process the packet and route it.

  • Smooth Transition

Large IP address scheme in IPv6 enables to allocate devices with globally unique IP addresses. This mechanism saves IP addresses and NAT is not required. So devices can send/receive data among each other.

Another fact is, the header is less loaded, so routers can make forwarding decisions and forward them as quickly as they arrive.

  • Extensibility

One of the major advantages of IPv6 header is that it is extensible to add more information in the options part. IPv4 provides only 40-bytes for options, whereas options in IPv6 can be as much as the size of IPv6 packet itself

Disadvantages of IPv6
  • IPv4 remains more popular
  • IPv6 and IPv4 can’t communicate directly and requires a server
  • VPN providers have been unresponsive in upgrading servers to support IPv6

Due to the many advantages/features of IPv6, the majority of network engineers, data centres, tech companies, and mobile carriers utilize IPv6. IPv6 is the preferred choice for professionals, and it should be for the average user as well.

So, as it currently stands, IPv4 addresses can still be purchased and assigned, but the numbers will continue to dwindle over the next few years, which will create issues. Initiating IPv6 resolves the problem.

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