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EDIT: Looks like I was wrong when I thought IPv6 was backwards compatible IPv6 is backwards compatible so why would we "finally roll off IPv4"? IPv6 has been "

EDIT: Looks like I was wrong when I thought IPv6 was backwards compatible IPv6 is backwards compatible so why would we "finally roll off IPv4"? IPv6 has been "here" in production for over a decade, and has seen slow adoption. I suspect it may be another 8-10 years until IPv6 gets close to a majority, but wouldn't IPv4 still be in-use? What would force a roll off of IPv4? Either way, I too would like to know more about how IPv4 space has appreciated/depreciated in the past decade

lucb1e 6y ago
In what way is it backwards compatible? It's not as if all allocations are kept and people just add 96 bits to their existing addresses. They are completely disjoint address spaces and protocols, as compatible as Tor is with the general internet: to communicate between the two, you need a proxy.
- mulmen 6y ago
  Tor operates over the Internet. Did you mean to compare Tor to the World Wide Web?
  - eznzt 6y ago
    Tor is sort of a virtual network. You need a gateway between the virtual network and the Internet to access the Internet.
    - mulmen 6y ago
      Tor overlays the Internet. It can’t operate without that underlying network. That is not how IPv6 works relative to IPv4.
      - lucb1e 6y ago
        Yeah, that is indeed a flaw in the comparison.
- sushicalculus 6y ago
  I was wrong. I must have rememberd an early draft or the translation layer
- Dylan16807 6y ago
  So I'm not saying it's backwards compatible, exactly, but what would you call 64:ff9b::?
  - mulmen 6y ago
    A reserved gateway address space? https://en.m.wikipedia.org/wiki/NAT64 https://en.m.wikipedia.org/wiki/NAT64
    - Dylan16807 6y ago
      By embedding the IPv4 address space inside the IPv6 address space. They are different protocols but they are not disjoint address spaces. You add 96 bits to the address and boom it's converted.
otterley 6y ago
IPv6 is not backwards compatible - it is a completely separate networking stack for all devices. And routers that speak only IPv4 have no idea what to do with IPv6 traffic. Similarly, IPv6-only endpoints cannot communicate with IPv4 endpoints without some sort of 6-to-4 gateway between them.
- bluGill 6y ago
  There shouldn't be any IPv4 only routers in the wild anymore. That isn't to say they aren't out there, only that anyone who has one is negligent in not updated/replacing it within the last 15 years or so. IPv6 is not a new thing, it was already live in 1996 (my memory might be a little off, but not much). Maybe you have turned off IPv6, but it should be supported and any competent IT should have a plan to turn it on (it might be a 5 year plan without any budget, but the plan should exist). Likewise you should have a plan to turn off IPv4 (if this plan has a budget it should be paid for entirely by the sale of your existing IPv4 block - this is mostly the business costs of IPv4 only customers being unable to reach you NOT the technical cost of updating all your servers)
linuxftw 6y ago
The problem isn't supporting IPv6, the problem is often having to support both 4 and 6 simultaneously. There's just a ton of work to get a single IP stack working on infrastructure, and it's more than twice the work to get 2 working in tandem.
- CountSessine 6y ago
  Is it really? In 2020? What examples are there? I worked on network switches at a major switch manufacturer and our IPv6 setup mostly just came along for the ride (or at least I thought it did - maybe our customers thought differently!) (Genuinely interested in hearing war stories from the front on this)
  - linuxftw 6y ago
    Just look at the amount of engineering effort and time that has gone into projects like kubernetes: https://github.com/kubernetes/enhancements/issues/508 https://github.com/kubernetes/enhancements/issues/508 That's just for IPv6 support, which is beta, and took years to get there. Dual Stack is still in alpha, and that didn't appear until a really recent release (1.16). I think routers and switches are probably the easier pieces of the puzzle, at least as far as managing them goes. The vendors have worked out all the kinks (hopefully?) before the equipment gets to you. That's just to get the stuff to work. Then you have corporate/government policies and validation. Then you have to solve problems like "My VM resolves things to IPv6 by default, but I have no IPv6 gateway so everything times out". And then make sure that logic makes it up through your entire stack. Multicast? Not allowed on many networks. Is it the end of the world? No. It's just a lot of extra work for everyone.
    - CountSessine 6y ago
      Yeah - that’s been my intuition, too. First we got software support in switches. Then OS network stacks started to support it. Then we got hardware switching chips that supported it. But the application and deployment layers just seem to be super hard. Just look at how hard it’s been to get IPv6 on AWS. Someday, hopefully!
xnyan 6y ago
>IPv6 is backwards compatible It would be really really great if true, unfortunately this is not correct. IPv6 SHOULD have been this way, but The Powers That Be took it as an opportunity to "correct" other IPv4 issues and now we have what we have.
- TheDong 6y ago
  > IPv6 SHOULD have been this way How would it have possibly been backwards compatible? Plenty of routers and ip-aware switches have, in hardware, specified that ips are 32-bits, so anything that added more bits would necessarily break existing hardware, and thus not be backwards compatible. That's not to mention all the software that has similarly hardcoded the number of bytes in an ip. How could we possibly have made ipv6 backwards compatible?
  - bluGill 6y ago
    I worked on the first switch ever sold in 1995 - it didn't support IPv6, but I assure you all the engineers working on it were aware of IPv6 and assumed IPv4 would be long gone by today. For reference back then we were more concerned about how the switch handled IPX (Novell Netware) than IP. Everything else since then was designed in the era where IPv6 is coming soon enough that you ensure you can support it with a software update if you don't support it. That isn't to say IPv6 couldn't have been done in a backward compatible way. I can think of ways to do that, and dozens of pros and cons - even though I haven't been in networking for 20 years and so I've forgotten a lot.
    - TheDong 6y ago
      > ensure you can support it with a software update if you don't support it For hardware, that doesn't sound that different from not supporting it. Convincing end-users of internet hardware to update their switch's firmware is hard. Ubiquiti has done a pretty good job of making updates actually doable, but for most hardware I doubt it'd happen more quickly than the hardware itself would fail. > That isn't to say IPv6 couldn't have been done in a backward compatible way. I can think of ways to do that Can you explain any of those ways?
Arnt 6y ago
The only realistic reason to get rid of IPv4 is its unreliability, if significant. 15-20 years ago IPv6 routing was often tunneled over v4, and it was noticeably less reliable than v4. Nowadays v6 is a touch faster/more reliable than v4, not very much. If that difference widens much and most users have v6 anyway, then v4 might get the axe. Otherwise... I don't think so. FWIW I already operate some v6-only services. Not for the general audience. An SSH bastion host, a backup service, that kind of thing, not web sites for the general audience. I'm not in the least surprised if some warez topsite is v6-only already.

lucb1e 6y ago

In what way is it backwards compatible? It's not as if all allocations are kept and people just add 96 bits to their existing addresses. They are completely disjoint address spaces and protocols, as compatible as Tor is with the general internet: to communicate between the two, you need a proxy.

mulmen 6y ago
Tor operates over the Internet. Did you mean to compare Tor to the World Wide Web?
- eznzt 6y ago
  Tor is sort of a virtual network. You need a gateway between the virtual network and the Internet to access the Internet.
  - mulmen 6y ago
    Tor overlays the Internet. It can’t operate without that underlying network. That is not how IPv6 works relative to IPv4.
    - lucb1e 6y ago
      Yeah, that is indeed a flaw in the comparison.
sushicalculus 6y ago
I was wrong. I must have rememberd an early draft or the translation layer
Dylan16807 6y ago
So I'm not saying it's backwards compatible, exactly, but what would you call 64:ff9b::?
- mulmen 6y ago
  A reserved gateway address space? https://en.m.wikipedia.org/wiki/NAT64 https://en.m.wikipedia.org/wiki/NAT64
  - Dylan16807 6y ago
    By embedding the IPv4 address space inside the IPv6 address space. They are different protocols but they are not disjoint address spaces. You add 96 bits to the address and boom it's converted.

otterley 6y ago

IPv6 is not backwards compatible - it is a completely separate networking stack for all devices. And routers that speak only IPv4 have no idea what to do with IPv6 traffic. Similarly, IPv6-only endpoints cannot communicate with IPv4 endpoints without some sort of 6-to-4 gateway between them.

bluGill 6y ago
There shouldn't be any IPv4 only routers in the wild anymore. That isn't to say they aren't out there, only that anyone who has one is negligent in not updated/replacing it within the last 15 years or so. IPv6 is not a new thing, it was already live in 1996 (my memory might be a little off, but not much). Maybe you have turned off IPv6, but it should be supported and any competent IT should have a plan to turn it on (it might be a 5 year plan without any budget, but the plan should exist). Likewise you should have a plan to turn off IPv4 (if this plan has a budget it should be paid for entirely by the sale of your existing IPv4 block - this is mostly the business costs of IPv4 only customers being unable to reach you NOT the technical cost of updating all your servers)

linuxftw 6y ago

The problem isn't supporting IPv6, the problem is often having to support both 4 and 6 simultaneously. There's just a ton of work to get a single IP stack working on infrastructure, and it's more than twice the work to get 2 working in tandem.

CountSessine 6y ago
Is it really? In 2020? What examples are there? I worked on network switches at a major switch manufacturer and our IPv6 setup mostly just came along for the ride (or at least I thought it did - maybe our customers thought differently!) (Genuinely interested in hearing war stories from the front on this)
- linuxftw 6y ago
  Just look at the amount of engineering effort and time that has gone into projects like kubernetes: https://github.com/kubernetes/enhancements/issues/508 https://github.com/kubernetes/enhancements/issues/508 That's just for IPv6 support, which is beta, and took years to get there. Dual Stack is still in alpha, and that didn't appear until a really recent release (1.16). I think routers and switches are probably the easier pieces of the puzzle, at least as far as managing them goes. The vendors have worked out all the kinks (hopefully?) before the equipment gets to you. That's just to get the stuff to work. Then you have corporate/government policies and validation. Then you have to solve problems like "My VM resolves things to IPv6 by default, but I have no IPv6 gateway so everything times out". And then make sure that logic makes it up through your entire stack. Multicast? Not allowed on many networks. Is it the end of the world? No. It's just a lot of extra work for everyone.
  - CountSessine 6y ago
    Yeah - that’s been my intuition, too. First we got software support in switches. Then OS network stacks started to support it. Then we got hardware switching chips that supported it. But the application and deployment layers just seem to be super hard. Just look at how hard it’s been to get IPv6 on AWS. Someday, hopefully!

xnyan 6y ago

>IPv6 is backwards compatible It would be really really great if true, unfortunately this is not correct. IPv6 SHOULD have been this way, but The Powers That Be took it as an opportunity to "correct" other IPv4 issues and now we have what we have.

TheDong 6y ago
> IPv6 SHOULD have been this way How would it have possibly been backwards compatible? Plenty of routers and ip-aware switches have, in hardware, specified that ips are 32-bits, so anything that added more bits would necessarily break existing hardware, and thus not be backwards compatible. That's not to mention all the software that has similarly hardcoded the number of bytes in an ip. How could we possibly have made ipv6 backwards compatible?
- bluGill 6y ago
  I worked on the first switch ever sold in 1995 - it didn't support IPv6, but I assure you all the engineers working on it were aware of IPv6 and assumed IPv4 would be long gone by today. For reference back then we were more concerned about how the switch handled IPX (Novell Netware) than IP. Everything else since then was designed in the era where IPv6 is coming soon enough that you ensure you can support it with a software update if you don't support it. That isn't to say IPv6 couldn't have been done in a backward compatible way. I can think of ways to do that, and dozens of pros and cons - even though I haven't been in networking for 20 years and so I've forgotten a lot.
  - TheDong 6y ago
    > ensure you can support it with a software update if you don't support it For hardware, that doesn't sound that different from not supporting it. Convincing end-users of internet hardware to update their switch's firmware is hard. Ubiquiti has done a pretty good job of making updates actually doable, but for most hardware I doubt it'd happen more quickly than the hardware itself would fail. > That isn't to say IPv6 couldn't have been done in a backward compatible way. I can think of ways to do that Can you explain any of those ways?

Arnt 6y ago

The only realistic reason to get rid of IPv4 is its unreliability, if significant. 15-20 years ago IPv6 routing was often tunneled over v4, and it was noticeably less reliable than v4. Nowadays v6 is a touch faster/more reliable than v4, not very much. If that difference widens much and most users have v6 anyway, then v4 might get the axe. Otherwise... I don't think so. FWIW I already operate some v6-only services. Not for the general audience. An SSH bastion host, a backup service, that kind of thing, not web sites for the general audience. I'm not in the least surprised if some warez topsite is v6-only already.