IPv4 vs. IPv6 FAQ

&gt; Why isn’t IPv6 more popular? ... and an arguably overly complex design.<p>I really don&#x27;t know where this ridiculous claim comes from. Yes, IPv6 addresses <i>look</i> more complicated but various other things about the protocol are drastically simplified — no more on-path fragmentation, simpler header formats and fewer required header fields, correctly implemented link-local scopes, previously separate ICMP+ARP+IGMP protocols consolidated into ICMPv6 (which handles neighbour discovery, router advertisements, path MTU discovery and multicast group membership amongst others), no more broadcast, and in many cases clients will quite happily get along without DHCP. If anything, it is considerably less complex.

My issue with IPv6 is that its designers assume that everyone with an IPv6 network will get static IPv6 addresses.<p>However, it didn’t turn out that way in the real world. Every time my router resets, all of the IPv6 addresses in my home network change. So, I don’t use IPv6 to connect among computers in my home network; since I <i>also</i> get one IPv4 address from my ISP, I simply use IPv4 NAT so that the addresses in my home network are easily remembered and do not change.<p>The reason I don’t use IPv6 and 6:6 NAT is because the IPv6 designers feel this makes networking too complicated, never mind that NAT is a solved problem, so 6:6 NAT support just really isn’t there.<p>Another annoyance I have with IPv6 is that it needs to have more than one localhost IP address, considering that IPv4 has a 24-bit space for localhost. A large number of localhost addresses is useful for network regression tests (e.g. if we have one authoritative DNS server on 127.10.0.1 and one which isn’t responding on 127.10.0.2, does our recursive DNS server on 127.12.0.1 correctly handle an upstream DNS server being down? Nice to be able to run the test using only localhost IPs; also nice to be able to change the IPs each test so we don’t have to wait for the kernel to release TCP sockets for a given IP + port).<p>For the record, I have gone to a lot of effort to give my open source networking software IPv6 support.

To me the most important thing about IPv6 is how it enables reliable peer to peer networks. IPv4 is the bane of existence to p2p networks since you have to so much extra shit to make it work (Public address discovery, NAT hole punching, relaying connections through some machine with an open port).<p>With IPv6 you can just stick your address on a DHT and peers can connect to you 100% of the time, no matter what.<p>The only thing that sucks is that you can&#x27;t count on an internet-connceted device having IPv6 yet.

&gt;Empirically, some ISPs route IPv4 more efficiently and some route IPv6 more efficiently.<p>It is so refreshing to see this written down somewhere. All of the academic papers I&#x27;ve seen comparing the empirical routing performance between IPv4 and IPv6 show a negligible performance difference. However, in the two states I&#x27;ve lived where I have looked at IPv6 vs IPv4 performance I see consistently higher pings with IPv6. Traceroute reveals that each individual hop adds the about the same amount of latency, but there are ~15% more hops for IPv6.<p>If I play a competitive game then I don&#x27;t want to be adding 10 ms of latency unnecessarily. So I just disable IPv6 on my gaming rig? C&#x27;mon. We can do better.

I firmly believe IPv6 adoption is hindered by one little reason more than any other: i can&#x27;t easily remember an ipv6 address. Its too big, its in hex, and that adds friction to everything. With v4 i can just look at an ip, remember it for a second and type it into whatever config&#x2F;program&#x2F;etc i need. I can tell a colleague across the room &quot;that ip is:...&quot;. I know there&#x27;s the condensed address format, but that just makes communicating it harder. Typo `::` as `:`? Now you have a problem that&#x27;s not easy to see.<p>Its a small friction, but it adds up quickly and makes working with ipv6 feel sluggish and painful.<p>(A common response when i say this is &quot;isn&#x27;t that what DNS is for?&quot; and yes, it is. That&#x27;s great once you have DNS and reverse DNS working, but &quot;its always dns&quot; is a meme for a reason).

ISP&#x27;s and networks love clients being behind NAT, so they can&#x27;t directly host to the outside world and can&#x27;t rely on a static address. Ipv4 is a scarce resource, therefore it&#x27;s valuable. Various people don&#x27;t want that to go away. The only way we&#x27;re going to get ipv6 everywhere is when the feds start requiring it.<p>The internet being a world resource should be of significant concern to every country. The limited number of ipv4 resources is a weakness of the U.S. and othe western countries. As is the lack of &quot;cyber security&quot;.

I&#x27;m curious when we&#x27;ll declare some sort of &quot;idea bankruptcy&quot; on IPv6, develop a new version (IPv7?) that has a &quot;ease of migration from IPv4&quot; as a stated goal, and deploy&#x2F;implement that.<p>Knowing the historical transition issues collected over the past 20 years, we could, as an industry and society, design a next generation and provide a reasonable rollout target of, say, 2030, and move towards that.<p>Since 1998&#x2F;99, there&#x27;s been an explosion of networking, and large cultural shifts (billions of mobile devices, IoT, etc) which were not around when all this was specced out. No technology adopted IPv6 as a default during that time, and I dare say most things (services, devices, etc) aren&#x27;t even tested against IPv6.<p>After 20+ years of this, I see IPv6 as a failure, even if there is 30-50% adoption (or perhaps because of those figures).

<i>&gt; Should I support IPv6 on my server?<p>&gt; You can if you want, but despite what some people will claim, it probably won’t make much difference.</i><p>This apathy is exactly why adoption is slow. For all its faults Google needs to be commended for their commitment to IPv6. They are the only large email provider I see sending and receiving email using IPv6 even though &quot;it probably won’t make much difference&quot;

&gt; IPv6 has several advantages, including a much larger address space. IPv4 had only 2^32 addresses, less than one per person on earth. IPv6 has 2^128 addresses, an immensely larger number which is not expected ever to be exhausted. Estimates are that this is enough to assign 100 IPv6 addresses to every atom on earth.<p>Yeah, so that&#x27;s overestimating the number of IPv6 addresses by quite a couple of orders of magnitude. This website estimates the number of atoms at 10^49 to 10^50, whereas 2^128 is in the order of 3 * 10^38. <a href="https:&#x2F;&#x2F;www.fnal.gov&#x2F;pub&#x2F;science&#x2F;inquiring&#x2F;questions&#x2F;atoms.html" rel="nofollow">https:&#x2F;&#x2F;www.fnal.gov&#x2F;pub&#x2F;science&#x2F;inquiring&#x2F;questions&#x2F;atoms.h...</a> Perhaps the writer was thinking of grains of sand instead of atoms? I&#x27;m not sure how many sand we have, but it&#x27;s probably more in the 2^128 ballpark.

I&#x27;ve been playing with IPv6 for over a decade. My observations are that it&#x27;s actually faster across the backbone. I&#x27;m not sure why this is.<p>A very useful site: <a href="https:&#x2F;&#x2F;ipv6-test.com&#x2F;" rel="nofollow">https:&#x2F;&#x2F;ipv6-test.com&#x2F;</a>

&gt;The primary purpose of IPv6 was to expand the address space of IPv4.<p>I wish this were all it did. People can make arguments about IPv6 being &quot;simpler,&quot; but it&#x27;s often not simpler in practice:<p>- You still need to run dual-stack - You need to re-learn a lot of your networking fundamentals - Despite IPv6 being effectively infinite, most ISPs will not give you a static IP - Most hardware is built for IPv4 and NOT IPv6 - Local subnetting is far more complicated. Not just due to the the length of the address, but due to the fact that you often need to work out SLAAC and&#x2F;or have a local DNS service to handle the address changes.

As someone who experience many problems with Multicast on IPv4 &#x2F; IPv6 hybrid networks, how different are the implementation of Broadcasting on each protocol?<p>Mostly I came aware that in IPV4 the router tries to create a local multicast group, using IGMP snooping you can solve some problems to get your broadcast thru multiple devices, but in IPv6 this is kind of confusing to me... does any one has information on this?

&gt; At Tailscale we believe the main reason for the slow IPv6 rollout is that it simply has not been able to provide enough direct value, when deployed as a hybrid in parallel with IPv4. The intention was to deploy IPv6, then retire IPv4 completely, in which case IPv6 would have made the Internet overall simpler and cheaper to manage, which is a big benefit. Unfortunately, this value doesn’t materialize until the very end, after IPv6 has been fully deployed to billions of devices. This means companies usually will not recoup the costs of IPv6 deployment on a predictable timeline, which makes investment hard.<p>Anyone else get a strong climate change parallel vibe from this section? Hopefully the stronger (dis)incentives of a slower rollout of carbon reduction efforts will be able to overcome some of these same obstacles.

Well it appears that routing to google from home is pretty much the same:<p>ping google.com round-trip min&#x2F;avg&#x2F;max&#x2F;stddev = 5.925&#x2F;7.695&#x2F;10.634&#x2F;2.093 ms<p>ping6 google.com round-trip min&#x2F;avg&#x2F;max&#x2F;std-dev = 6.348&#x2F;8.013&#x2F;10.869&#x2F;1.965 ms<p>traceroute and traceroute6 both had 8 hops.

&gt; <i>What would a backward-compatible address extension to IPv4 look like?</i><p>See also: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;IPv6_transition_mechanism" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;IPv6_transition_mechanism</a>

I&#x27;m on linux... Is there some document on how I can tell if i&#x27;m getting ipv6, a description of what i&#x27;m seeing or what to expect, and what I can do with it that is cool?

For anyone wondering why they cant access their ipv6-addressed pi box from public WiFi networks: those public networks still use ipv4 and assign you only a lonk-local ipv6 address.<p>To go from 4 to 6, the public WiFi box will need to use a 4 to 6 &quot;broker&quot; and there are surprisingly few of these around and they&#x27;re not usually free.<p>So basically, your home network and Pi is future-ready, but public infrastructure might need a moment...

Let’s get 128 bits but give everyone a &#x2F;48 and so have only 16 bits more effectively wooohooo<p>Shoulda gone for 1024 bits and made people really whine

Sidenote to all of this, an IPv4-compatible upgrade path in 1992: <a href="https:&#x2F;&#x2F;datatracker.ietf.org&#x2F;doc&#x2F;html&#x2F;rfc1347" rel="nofollow">https:&#x2F;&#x2F;datatracker.ietf.org&#x2F;doc&#x2F;html&#x2F;rfc1347</a>