IPv6 Pain Experiment

Sun Oct 6 20:57:24 UTC 2019

On October 6, 2019 at 15:18 mpalmer at hezmatt.org (Matt Palmer) wrote:
 > On Sat, Oct 05, 2019 at 04:36:50PM -0400, bzs at theworld.com wrote:
 > > 
 > > On October 4, 2019 at 15:26 owen at delong.com (Owen DeLong) wrote:
 > >  > 
 > >  > OK… Let’s talk about how?
 > >  > 
 > >  > How would you have made it possible for a host that only understands 32-bit addresses to exchange traffic with a host that only has a 128-bit address?
 > > 
 > > A bit in the header or similar (version field) indicating extending
 > > addressing (what we call IPv6, or similar) is in use for this packet.
 > 
 > How does that allow the host that only understands 32-bit addresses to
 > exchange traffic with a host which sets this header bit?

As I said, it doesn't, but it lets each host decide that rather than
the router tho if the host just knows enough to copy out the entire
src/dst address (imagine the bits beyond the first 32 were in
something like an extended ICMP options field w/in the IP header) then
the rest could operate identically to ipv4.

So all you'd need added to a host IPv4 stack would be if you see this
extended addressing flag/bit/whatever then there's more that needs to
be copied out to each outgoing IP packet.

It would be the routers' job to interpret those extra bits for routing.

-- 
        -Barry Shein

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