Re: [v6ops] draft-smith-v6ops-local-only-addressing

[Brian E Carpenter <[e-mail]>]

A few somewhat random comments:

1. A nit, but a major nit: the use of the word "global".

Repeat after me: ULAs are global scope addresses. They are explicitly defined as having global scope in RFC4193.

Also repeat after me: ULAs are not globally reachable addresses. They are explicitly forbidden to be routed globally by RFC4193.

Yes, this could be confusing; that's why we have RFC8190. But each occurrence of "global" in the draft needs to be reviewed, and if appropriate, replaced by either "with global scope" or "globally reachable". For example, the last sentence of the Abstract should be: "This memo proposes that these types of devices refuse to configure and use globally reachable IPv6 Internet addresses by default."

2.

> 2.  Default Local Only Addresses
> 
>    By default, a Local Only Address device MUST only configure Link-
>    Local and non-global IPv6 addresses, currently Unique Local Addresses
>    [RFC4193], on its network interfaces.

That will fail if the router doesn't announce a ULA prefix. What do you want the default behaviour to be in that case?

OK, I see that you cover this point later under SLAAC but it seems to me that it is a general that point should be covered here. And I think your recommendation is broken from a practical point of view: if a device is installed on a routed network that does not announce a ULA prefix, limiting it to link-local is simply broken as it prevents the devices from being accessed by devices on other subnets.

So I think the only practical proposal is that if and only if both ULA and globally reachable prefixes are announced, the device should configure only a ULA.

> 5.  Permitted Incoming and Outgoing Connections
> 
>    By default, a Local Address Only device MUST NOT accept any upper
>    layer connections from any global IPv6 addresses.

This is a case where s/global/globally reachable/ is essential. I agree with it, although default settings in many CE routers will already do this.

You probably need to discuss "call home" scenarios, which many vendors want to include in their products and which clearly need globally reachable addresses.

Finally, I think there are points mentioned in https://tools.ietf.org/html/draft-ietf-v6ops-ula-usage-considerations-02#section-4.2 and even in RFC4864 that should be considered.

Regards
   Brian