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Yes, but let's not pretend that IPv6 was just IPv4 with a larger addr size. A lot of other unnecessary cruft got changed. That is kinda the issue. Add an extra

Yes, but let's not pretend that IPv6 was just IPv4 with a larger addr size. A lot of other unnecessary cruft got changed. That is kinda the issue. Add an extra octet to IPv4, call it IPv5. Done. DHCP (as is) can already handle variable-length addresses so it'll work unmodified for 5-byte addrs, for example. Same for ARP.

thesnide 4y ago
I am wondering if we could hack the ipip tunnel to automagically handle a bigger address space. Much akin to your idea but mostly supported already
wvenable 4y ago
But the IPv6 changes are actually good, right? IPv4 was designed for an entirely different world and IPv6 was designed for this world. You're only going to get one chance to make these kind of improvements.
- tristanbvk 4y ago
  IPv6 has link-local, v4 doesn't. That is a huge configuration win.
  - sigjuice 4y ago
    IPv4 also has link-local addresses. They belong to the range 169.254.0.0/16.
    - tristanbvk 4y ago
      And is it enabled by default? Also is it mathematically unique not to cause any potential conflicts.
      - sigjuice 4y ago
        Yes. 169.254.0.0/24 addresses show up quite often.
lmm 4y ago
> Yes, but let's not pretend that IPv6 was just IPv4 with a larger addr size. A lot of other unnecessary cruft got changed. Mostly removed (e.g. removing fragmentation). If you're making an incompatible protocol, might as well take the chance to remove the cruft. > Add an extra octet to IPv4, call it IPv5. Done. Have fun debugging nondeterministic routing loops lol.
- toast0 4y ago
  Fragmentation is mostly removed on IPv4 as well. Almost everything sends DF, and there's very little legitimate fragmented traffic. You can just drop fragments wherever convenient. If you want to be nice, it's a good idea to have a small reassembly buffer, but if it's too much work, just drop them. It's beyond too late to change anything, but I imagine if IPv6 had started with a sensible rollout plan and worked backward from there, it would look somewhat different and it would have taken a lot less time to take hold.
  - sigjuice 4y ago
    IPv6 doesn't remove fragmentation. IPv6 fragmentation works differently. See https://www.rfc-editor.org/rfc/rfc8200#section-4.5 https://www.rfc-editor.org/rfc/rfc8200#section-4.5 The Fragment header is used by an IPv6 source to send a packet larger than would fit in the path MTU to its destination. (Note: unlike IPv4, fragmentation in IPv6 is performed only by source nodes, not by routers along a packet's delivery path -- see Section 5.)

thesnide 4y ago

I am wondering if we could hack the ipip tunnel to automagically handle a bigger address space. Much akin to your idea but mostly supported already

wvenable 4y ago

But the IPv6 changes are actually good, right? IPv4 was designed for an entirely different world and IPv6 was designed for this world. You're only going to get one chance to make these kind of improvements.

tristanbvk 4y ago
IPv6 has link-local, v4 doesn't. That is a huge configuration win.
- sigjuice 4y ago
  IPv4 also has link-local addresses. They belong to the range 169.254.0.0/16.
  - tristanbvk 4y ago
    And is it enabled by default? Also is it mathematically unique not to cause any potential conflicts.
    - sigjuice 4y ago
      Yes. 169.254.0.0/24 addresses show up quite often.

lmm 4y ago

> Yes, but let's not pretend that IPv6 was just IPv4 with a larger addr size. A lot of other unnecessary cruft got changed. Mostly removed (e.g. removing fragmentation). If you're making an incompatible protocol, might as well take the chance to remove the cruft. > Add an extra octet to IPv4, call it IPv5. Done. Have fun debugging nondeterministic routing loops lol.

toast0 4y ago
Fragmentation is mostly removed on IPv4 as well. Almost everything sends DF, and there's very little legitimate fragmented traffic. You can just drop fragments wherever convenient. If you want to be nice, it's a good idea to have a small reassembly buffer, but if it's too much work, just drop them. It's beyond too late to change anything, but I imagine if IPv6 had started with a sensible rollout plan and worked backward from there, it would look somewhat different and it would have taken a lot less time to take hold.
- sigjuice 4y ago
  IPv6 doesn't remove fragmentation. IPv6 fragmentation works differently. See https://www.rfc-editor.org/rfc/rfc8200#section-4.5 https://www.rfc-editor.org/rfc/rfc8200#section-4.5 The Fragment header is used by an IPv6 source to send a packet larger than would fit in the path MTU to its destination. (Note: unlike IPv4, fragmentation in IPv6 is performed only by source nodes, not by routers along a packet's delivery path -- see Section 5.)