nanog mailing list archives

Re: IPv6 Pain Experiment


From: bzs () theworld com
Date: Sun, 6 Oct 2019 16:57:24 -0400


On October 6, 2019 at 15:18 mpalmer () hezmatt org (Matt Palmer) wrote:
On Sat, Oct 05, 2019 at 04:36:50PM -0400, bzs () theworld com wrote:

On October 4, 2019 at 15:26 owen () 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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