Re: [Int-area] Using ISO8473 as a network layer to carry flexible addresses

[Stewart Bryant <[e-mail]>]

> On 1 Mar 2021, at 20:08, Brian E Carpenter <[e-mail]> wrote:
> 
> 
> It would take but a minute to design a longer-address mechanism for IPv6, although I don't have space to include it in the margin of this email**. But it would take many years for it to be widely implemented and deployed, during which time the Internet would be opaque to such addresses.
> 
> 
> ** Basically, use a prefix such as fb00::/8 to indicate an extended address.

Hi Brian

Basically I think that this fails the backwards compatibility text.

It is perfectly legitimate to write an IPv6 forwarder as follows:

If MACaddress == me and MACtype == IPv6 pass packet to IPv6 forwarder

In IPv6 forwarder:

If version == IPv6 and Hop Limit not exceeded send bytes 24 to 39 to address lookup engine

Wait for address result and forward packet accordingly

Except that this forwarder would have sent a bunch of random junk to the ALE consisting of some of the SA and maybe some of the DA depending on their sizes.

So to stop an old and legitimately designed parser being fooled you really have to use a new MAC type and a new version and as soon as you do that you might as well design the packet optimally for the job at hand.

If the IPv6 designers had followed the strategy of both the Ethernet designers and the ISO8473 designers and put DA before SA then the elegant approach that you and others have  proposed at various times would have worked nicely.

Best regards

Stewart