Re: IPv6 Pain Experiment

[bzs () theworld com]

On October 6, 2019 at 16:35 jhellenthal () dataix net (J. Hellenthal) wrote:
> And in which part of the header is this to be added ?

I assume you mean the additional address. The IHL provides for up to
60 bytes of IP header length. 20 bytes is needed for the usual IPv4
header so an additional 40 bytes are available or 20 bytes for each of
source and destination, adding the 4 bytes already present that's 24
bytes for each of source and destination or a theoretical total of 192
bits of (each) source and dest address.

All a strictly IPv4 only host/router would need to understand in that
case is the IHL, which it does already, and how to interpret whatever
flag/option is used to indicate the presence of additional address
bits mostly to ignore it or perhaps just enough to know to drop it if
it's not implemented.

> -- 
>  J. Hellenthal
>
> The fact that there's a highway to Hell but only a stairway to Heaven says a lot about anticipated traffic volume.
>
> > On Oct 6, 2019, at 15:58, bzs () theworld com wrote:
> >
> > 
> > > 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
> >
> > Software Tool & Die    | bzs () TheWorld com             | http://www.TheWorld.com
> > Purveyors to the Trade | Voice: +1 617-STD-WRLD       | 800-THE-WRLD
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-- 
        -Barry Shein

Software Tool & Die    | bzs () TheWorld com             | http://www.TheWorld.com
Purveyors to the Trade | Voice: +1 617-STD-WRLD       | 800-THE-WRLD
The World: Since 1989  | A Public Information Utility | *oo*