Re: Reinventing Site-Locals

[Alexandre Petrescu <[e-mail]>]

Le 27/04/2019 à 04:19, Mark Smith a écrit :
[...]

>>>> (because the numerous computers in these three cars are not all on a
>>>> single subnet; they are all interconnected with IP, but there are
>>>> multiple subnets with routers in between).
>>>>
>>>
> 
> Right. This confirms my suspicion. If you got us to add Subnet IDs to
> Link-Local addresses, I'm confident you'd next be lobbying them to be
> routeable across different links attached to routers.

No, your assumption is wrong.

Let me reassure you, I want this: I want the link-local addresses to 
stay on a single link, in the same subnet.  Pinging them ok makes the 
logic of deciding whether the subnet set up was correctly done (channel 
number, MHz).

If these were ULAs, or site-locals, then the IP forwarding would have 
also played a role that is a difficult to consider.  It is not good to 
use IP forwarding to construct subnets, but to forward between them.

Again: I do not want site-locals.

> In other words, you'd want these Link-Local addresses to have a scope
> that is greater than a link.

No.  I want the link-local addresses that have a Subnet ID inside to 
have a link scope.

> We used to have an address space for that, called the Site-Local address space.
> 
> Read why they were deprecated and then replaced by ULAs in RFC 3879.

I was in the room, I voted no to deprecation.

But I then thid agree with the IETF recommendation and removed all 
site-locals from my deployment.  Then I also removed 6to4.  I am happy 
about these decisions.

But for SubnetID-in-LL the situation is different.

> You won't like that they're easy to type, however that is the cost of
> solving all of the issues described in RFC 3879.

No.

Given that I do not want Site Local addresses, as explained above, do 
you still want me to read RFC3879?

In turn, let me bring back your suspicion: you suspect the car network I 
build needs Site Locals because you think this is disconnected from the 
Internet.  Do you know why this car network is disconnected from the 
IPv6 Internet?

Alex