The new IPv6 features that are most often discussed are the new large address space, hierarchical addressing, and Quality of Service (QoS).
Latest posts by Michael Pietroforte (see all)

In the last post of my IPv6 series, I outlined the main reason why you should now get started with IPv6: IPv6 will come soon to your network whether you like it or not. Network engineers have a few other reasons to offer, and this is the topic of the next two articles. The new IPv6 features are not really new because the protocol has already existed for more than 10 years. For this reason, I won't just repeat the feature descriptions, which you can read on countless other sites, but I will outline my view about the significance of these enhancements.

Cisco Router

Large address space

While the other new IPv6 features are all nice to have, the new large address space is certainly the main (perhaps the only) reason why IPv6 will come. An IPv4 address consists of 32 bits; the IPv4 address space, therefore, allows 232 addresses. An IPv6 address is four times as long and has 128 bits. Thus, in theory, IPv6 allows 2128 = 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses. This corresponds to 655,570,793,348,866,943,898,599 (6.5x1023) addresses for every square meter of the Earth’s surface.

To be honest, I am not really impressed by these numbers. We are now entering the nano technology age, which means that we will have more and more, much smaller, communication devices than the IPv6 inventors have anticipated. Considering that a cubic meter of ideal gas contains around 1025 atoms, the number of 1023 IP addresses per square meter appears to be relatively small. I know this sounds like science fiction, but, for the inventors of IPv4, the Internet as we know it today certainly was science fiction at their time. We needed about 30 years to use up all of the IPv4 addresses. My gut tells me that the IPv6 addresses won't last that long.

Hierarchical addressing

The Internet address classes of IPv4 allow hierarchical addressing to a certain extent. Hierarchical addressing makes routing more efficient because it reduces the size of routing tables. However, considering that the computation power of routers increased at a higher rate than the growth of the Internet, this was not really a problem.

Nevertheless, it is quite likely that the Internet will now grow at a higher rate than ever before, not only because the total population of the emerging markets (especially China and India) far exceeds the population in the developed world but also because the new type of devices (mobile phones, tablets, ebook readers, TV sets, etc.) also require IP addresses. Thus IPv6's new hierarchical addressing capabilities are certainly important. And here the IPv6 inventors did not really scrimp. Of the 128 bits of an IPv6 address, 64 bits are used for hierarchical addressing, 48 bits for the public topology, and 16 bits for the site topology. The latter means that you can work with hierarchical addresses within your organization.

Better support for Quality of Service (QoS)

IPv4 has limited support for Quality of Service (QoS)—that is, real-time delivery of data through the Type of Service (TOS) field. One problem of QoS in IPv4 pertains to TCP and UDP port identification, which is not possible if the IPv4 packet is encrypted. The other problem is that QoS in IPv4 is not really standardized. The IPv6 header has the Flow Label field, which allows QoS handling that is independent of the payload.

While this new feature is technically interesting, in practice QoS is quite problematic for traffic on the public Internet. You might have heard of the stir that the alleged Google-Verizon deal caused. Google intended to pay Verizon to prioritize their traffic.

The main question is how you decide which traffic has priority. Is it justified that you have to wait for the latest 4sysops article to show up on your screen just because some teens clogged the net with their YouTube videos? And if you pay for QoS, how can you measure that your traffic really has a higher priority? One thing is for sure, if QoS really comes, then the complexity level of the Internet will be raised again by one or two bars, which means more work for IT pros.

In the next post I will talk about IPv6 IPsec and the IPv6 LAN features.

  1. bitfuzzy 6 years ago

    There are enough IPv6 addresses for every atom on the planet and your gut feeling is that it won’t last long??

    • Author

      An what about the atoms on Mars? Did you think about that? 😉

      Seriously, IPv6 provides 3.4×10^38 addresses and the number of atoms on earth is 1.33 x 10^50.  So you see, you missed the target by a couple of magnitudes and there are not as many IPv6 addresses as you thought.

      The internet inventors were unable to imagine that we will run out of IP addresses because engineers usually think linearly. However, IT grows exponentially. I think it is only a matter of time until want to communicate with nanobots via IP. Or perhaps we want to encode IP addresses in DNA molecules? And then we are already in the range of atom-sized objects. As Feynman said, “there’s plenty of room at the bottom.” And who says that every device will only need one address?

      The point is that whenever a technology grows exponentially, it is essentially impossible to predict how things develop. Thus, if the IPv6 creators were smart, they would have allowed a flexible address length. However, they made essentially the same mistake as the internet inventors.

  2. Dani 6 years ago

    Humanity wil go extinct long before we run out of ip6 addresses. Or more precisely when humanity is on the verge of extinction, only tiny part of ip6 address space will be utilized. Why ? large portion of ip6 address space will be utilized only if the world is full of gazillion*gazillion smart nano robots, each of them capable to communicate directly to each other. In such a world, humanity will transform to something completely different, if survive at all.

  3. Author

    You are right, once we have intelligent nanobots, humanity will transform in a new species. I suppose this new species will than be smarter than humans and design a protocol with an infinite number of addresses. By the way, it is not just nano technology that will cause a shortage of IPv6 addresses. Virtual devices almost need no space at all. And how about devices that no longer exist? Wouldn’t it be useful if we still could identify those devices in log files, ages after those devices have been destroyed? How many addresses will we need for this?


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