Reply to post: Re: IPv6 should have taken off by now

Internet engineers tear into United Nations' plan to move us all to IPv6

tip pc Silver badge

Re: IPv6 should have taken off by now

It's not explained well in the recommendation, but if you use the same subnetting plan for v4 and v6 and are careful to also use the same host IDs for dual stack devices (which involves limiting yourself to only the first 256 addresses of the v6 /64...) then it's possible to define a stateless translation rule between v4 and v6 IPs for those devices.

it'll look stateless to your eyes but it is in no way stateless for a network device. Network devices are optimised to work in hardware where possible and for IPv4 they know the address info starts at bit 96, your mapped IPv6 address will not be at bit 96 and so the IPv4 stack will have to be re written to recognise if its reading an IPv4 or IPv6 packet and look at bit 64 instead. All IPv4 stacks along the path will need rewriting to accommodate the change, and likley new firmware if the hardware can accommodate the change. If your going to do that then you may as well make them all IPv6.

https://en.wikipedia.org/wiki/IPv4#Packet_structure

https://en.wikipedia.org/wiki/IPv6_packet#Fixed_header

you can't force IPv4 to read an IPv6 packet as their structures are completely different.

At best you could design the IPv6 stack to recognise and work with an IPv4 packet but that'll likely just introduce vulnerabilities.

Don't forget this is just layer 3 addressing we are discussing. So long as the host traffic is being sent to can detect and use the appropriate stack for interpreting L3 addressing both addressing schemes can coexist on the L2 Lans & WANS as Ipv4 has done for decades. Its very important to understand and realise that L2 & L3 are distinct and that L3 overlays ontop of L2.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon