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Understanding the Need for IPv6 - How IPv6 Overcomes IPv4 Limitations

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Internet has been around in its current form since the 1980s. What started off as an in-house project in ARPA in 1958 rapidly expanded into what we know today as the Internet. IPv4 as a protocol has been in practice since the 1980s. Back then it was only designed to allocate addresses for a few billion, 4.3 billion to be exact. The Internet Assigned Numbers Authority (IANA) was in charge of allocating these addresses and it did so by sending them in blocks of 16.8 million. This it did by putting in place certain regional Internet registries or RIRs.

But as the popularity of the Internet grew exponentially, so did the need for more and more IP addresses. This already was becoming a problem in the late 1980s. Through time, as computers become more affordable and people wanted to be on the World Wide Web, the need was growing more acute. With more advancement of technology, today, phones, cameras, video game consoles and other devices are also joining the internet.

This added to the issue of the lack of IP addresses to allocate to this new breed of machines on the Internet. IANA officially exhausted its pool of addresses on 31st January 2011 and one RIR exhausted its on 15th April 2011. The rest are destined to run out within the next few years.

Guided by this sense of Internet catastrophe, the most logical solution to this problem was to create a new protocol, a protocol that would go where no protocol has gone before, or at least provide more internet addresses to use.

As is traditional in our networking community, prescribed by the Internet Engineering Task Force or IETF (the main promoter and developer of Internet standards), any new standard, method, behaviours, research and innovation needs to be published as a memorandum. This can include anything that involves or is applicable to the internet or internet related systems. It’s what they call a Request for Comment or an RFC.

Hence, an RFC was released in January 1995 that detailed the creation of a new protocol IPv6. This was called RFC 1752 and the opening lines said, and I quote “This document presents the recommendation of the IPng Area Directors on what should be used to replace the current version of the Internet Protocol.”

The solution was for IPv6 to accommodate the increased demand by providing a much larger address space, along with improved traffic routing and better security. Some of the salient features include:

Larger IP address space: IPv6 has 128-bit address space or 4 times more address bits than IPv4's 32-bit address space. This large address space is enough for many decades to come. In real terms, every residential or commercial customer will be able to receive more address space from TWC than the entire IPv4 address space contains – several billion IP addresses!

  • Better security: IPv6 includes security in the underlying protocol. For example, encryption of packets (ESP: Encapsulated Security Payload) and authentication of the sender of packets (AH: Authentication Header).
  • Consideration to real time: To implement better support for real-time traffic (such as videoconference), IPv6 includes a flow label mechanism so routers can more easily recognize where to send information.
  • Plug and play: IPv6 includes plug and play, which is easier for novice users to connect their machines to the network. Essentially, configuration will happen automatically.
  • Better optimization: IPv6 takes the best of what made IPv4 successful and gets rid of minor flaws and unused features.

The recommendation to create the next generation protocol was raised in the Toronto IETF conference. The main changes from IPv4 can be summarised as follows:

  • Expanded addressing capability and auto configuration mechanism: the address size in this protocol has been increased from 32 bit to 128 bit with deeper addressing hierarchy and simpler configurations. A new type of address called Anycast has been created to send a message to a single nearest member of a group.
  • Simplification of the header format and reduction in size: the header now has a fixed length of 40 bytes. Some header fields that were a part of IPv4 have been removed. They are discussed more in detail in the description of IPv6 header. This was done to improve on header processing time and forwarding techniques.
  • Improved support for extensions and options: unlike IPv4, the extensions in IPv6 are made optional and inserted between the header and the payload when needed. This improves flexibility and any new options in the future can be integrated easily.
  • Extensions for authentications and privacy: support for data authentications and data security has been specified.
  • Flow labelling capability: packets belonging to the same traffic flow needing special handling or security can be labelled by the sender.

So, in all, the proposal was adopted by IETF and implemented. The deployment of IPv6 is the only available solution to the IPv4 address shortage. IPv6 is endorsed and implemented by all Internet technical standards bodies and network equipment vendors. It encompassed many design improvements, including the replacement of the 32-bit IPv4 address format with a 128-bit address for a capacity of about 3.4×1038 addresses. IPv6 has been in active production deployment since June 2006.

In the next tutorial, IPv6 - Analysing the IPv6 Protocol Structure and IPv6 Header, we will see exactly how and why is IPv6 the next best thing since sliced bread, or in our world, the next best protocol!


About the Writer

Arani Mukherjee holds a Master’s degree in Distributed Computing Systems from the University of Greenwich, UK and works as network designer and innovator for remote management systems, for a major telecoms company in UK. He is an avid reader of anything related to networking and computing. Arani is a highly valued and respected member of, offering knowledge and expertise to the global community since 2005.

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