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This is a common misconception. Apart from the kind of NATs we have now, there is no way that IPv4 could have been expanded. A lot of routing hardware was ASIC

This is a common misconception. Apart from the kind of NATs we have now, there is no way that IPv4 could have been expanded. A lot of routing hardware was ASIC based (I'm sure plenty still is), so packet headers were fixed and couldn't be changed without changing all the routers. Just like they had to be changed with IPv6. Any server would need to understand the old system and the new system simultaneously to be able to be backwards compatible - just like with dual stack now. Big parts of the internet wouldn't be reachable until the host, the server, and every router and middle box along the path had been upgraded. Just like with IPv6. So you'd have all the same problems, just in a slightly different way...

magicalhippo 5y ago
> his is a common misconception. Apart from the kind of NATs we have now, there is no way that IPv4 could have been expanded. The misconception is that IPv4 could have been expanded in a compatible way. That's not GP's point though as I read it. They could have made an incompatible IPv5 which was exactly like IPv4, except with additional address bits. Then the operational side would be similar, and you wouldn't have to learn everything over again. Instead they changed just about everything.
- Nursie 5y ago
  I wonder if it's perhaps time to write off IPv6, for this reason, and come up with a different standard that is more like that. Because we're decades in here, and it's still not dominant, for the reasons given.
  - IshKebab 5y ago
    Based on this https://www.google.com/intl/en/ipv6/statistics.html#tab=ipv6-adoption https://www.google.com/intl/en/ipv6/statistics.html#tab=ipv6... we're probably 15-20 years away from "enough people have IPv6 that you can start dropping IPv4". There's zero chance you could make an IPv5 and have any adoption at all in that time.
  - p_l 5y ago
    You would start from scratch to develop chips that would support your new formats. IPv4+TCP and IPv6+TCP is literally baked into hard silicon on many, many devices, even if not for all phases of the protocol. We're talking redesigning switching chips, redesigning TCAM (content-addressable memories used to cache routes), etc. on top of designing yet another protocol. At least old IPv9 had the benefit of some level of support in sw/hw when it was proposed (as it reused CLNS from OSI for internetwork protocol)
- xxpor 5y ago
  >hey could have made an incompatible IPv5 which was exactly like IPv4, except with additional address bits. That exists, it's called enhanced IP or something. I'm having trouble finding it now since it's been a few years, but I've had a customer using it. Of course nothing besides the endpoints understood it, so it had to be wrapped in UDP. Horrible.
- WorldMaker 5y ago
  If you are going to have to break backward compatibility anyway, of course you are going to use that as a chance to change other things, fix some things that weren't broken but weren't great either, try for some nice to haves while you are at it. Especially if you were predicting a migration across any compatibility break would take decades or more (or potentially forever live side-by-side), there's very pragmatic reason "rip the bandaid off" and to change everything all at once rather than make a series of far more painful "smaller" migrations that would each individually take nearly as long.
- jandrese 5y ago
  IPv6 isn't that different than IPv4. Neighbor Discovery is just ARP. Not having in-path fragmentation and loads of other IPv4 legacy crap is a good thing. The only major change is that instead of the smallest routeable unit being a single address the smallest unit is now a whole 64 bit subnet so hosts have a bunch of bits they can use for various purposes. Network administrators don't have to worry about that for the most part, the hosts figure that out on their own. I guess there might be a security implication if someone has built their security system around knowing everything on the network via DHCP. But that was always a mistake. If you want real security you need to use 802.1x or similar. Being told you can't use DHCP to secure your network anymore is probably shock to some admins, but hopefully they take the opportunity to reconsider their system from the ground up.
  - unionpivo 5y ago
    There are a lot of changes needed, especially in (old) corporate environments. I do use ipv6 at home, and at some of our customers, but some of them would have to essentially redesign their entire networking/vpn/security plan (and yes, existing ones are not good, split horizon DNS is almost always present, DHCP is not only used for security, but also for provisioning, there are products that scan subnets and provide reports on devices required for various compliances ...). And that is a hard sell, for what they see as next to no benefits.

magicalhippo 5y ago

> his is a common misconception. Apart from the kind of NATs we have now, there is no way that IPv4 could have been expanded. The misconception is that IPv4 could have been expanded in a compatible way. That's not GP's point though as I read it. They could have made an incompatible IPv5 which was exactly like IPv4, except with additional address bits. Then the operational side would be similar, and you wouldn't have to learn everything over again. Instead they changed just about everything.

Nursie 5y ago
I wonder if it's perhaps time to write off IPv6, for this reason, and come up with a different standard that is more like that. Because we're decades in here, and it's still not dominant, for the reasons given.
- IshKebab 5y ago
  Based on this https://www.google.com/intl/en/ipv6/statistics.html#tab=ipv6-adoption https://www.google.com/intl/en/ipv6/statistics.html#tab=ipv6... we're probably 15-20 years away from "enough people have IPv6 that you can start dropping IPv4". There's zero chance you could make an IPv5 and have any adoption at all in that time.
- p_l 5y ago
  You would start from scratch to develop chips that would support your new formats. IPv4+TCP and IPv6+TCP is literally baked into hard silicon on many, many devices, even if not for all phases of the protocol. We're talking redesigning switching chips, redesigning TCAM (content-addressable memories used to cache routes), etc. on top of designing yet another protocol. At least old IPv9 had the benefit of some level of support in sw/hw when it was proposed (as it reused CLNS from OSI for internetwork protocol)
xxpor 5y ago
>hey could have made an incompatible IPv5 which was exactly like IPv4, except with additional address bits. That exists, it's called enhanced IP or something. I'm having trouble finding it now since it's been a few years, but I've had a customer using it. Of course nothing besides the endpoints understood it, so it had to be wrapped in UDP. Horrible.
WorldMaker 5y ago
If you are going to have to break backward compatibility anyway, of course you are going to use that as a chance to change other things, fix some things that weren't broken but weren't great either, try for some nice to haves while you are at it. Especially if you were predicting a migration across any compatibility break would take decades or more (or potentially forever live side-by-side), there's very pragmatic reason "rip the bandaid off" and to change everything all at once rather than make a series of far more painful "smaller" migrations that would each individually take nearly as long.
jandrese 5y ago
IPv6 isn't that different than IPv4. Neighbor Discovery is just ARP. Not having in-path fragmentation and loads of other IPv4 legacy crap is a good thing. The only major change is that instead of the smallest routeable unit being a single address the smallest unit is now a whole 64 bit subnet so hosts have a bunch of bits they can use for various purposes. Network administrators don't have to worry about that for the most part, the hosts figure that out on their own. I guess there might be a security implication if someone has built their security system around knowing everything on the network via DHCP. But that was always a mistake. If you want real security you need to use 802.1x or similar. Being told you can't use DHCP to secure your network anymore is probably shock to some admins, but hopefully they take the opportunity to reconsider their system from the ground up.
- unionpivo 5y ago
  There are a lot of changes needed, especially in (old) corporate environments. I do use ipv6 at home, and at some of our customers, but some of them would have to essentially redesign their entire networking/vpn/security plan (and yes, existing ones are not good, split horizon DNS is almost always present, DHCP is not only used for security, but also for provisioning, there are products that scan subnets and provide reports on devices required for various compliances ...). And that is a hard sell, for what they see as next to no benefits.