Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)

Philip Homburg <> Fri, 08 January 2021 16:55 UTC

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Subject: Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
From: Philip Homburg <>
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In-reply-to: Your message of "Fri, 8 Jan 2021 07:39:57 -0500 ." <>
Date: Fri, 08 Jan 2021 17:55:45 +0100
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>    I think link identifiers as you describe might be useful for
>    some applications, but putting them in a database has a lot of
>    issues. If every router on a link multicasts a link identifier
>    to a link, then it's not a link identifier--it's a router
>    interface identifier. That's fine, but now my node has to track
>    what router interface identifiers are present on the link, and
>    publish its information on each identifier. 

I'm confused here. I thought that one of the purposes of HNCP is to 
uniquely number each link with a /64.

If you have a unique 64 bit identifier, then it is trivial to compute
a unique domain name.

>    Furthermore, DNS has TTLs. What's the TTL on the data? How
>    quickly does it fall out of your cache? Remember, you wanted to
>    do this because Caching Is Good, so if you use a short TTL, your
>    Good Caching isn't happening.

What kind of topology changes are you thinking of that are faster than
typical DNS TTLs?

>    What if you're on an IPv4-only link? How do you publish your
>    IPv6 LLA with a router link identifier? Your router isn't giving
>    you one. You can't use the RFC1918 subnet prefix you got from
>    DHCP as a link identifier, because they are non-unique.

It seems to me that if you are doing homenet, you can just as well use 
RAs to distribute information. No need to do SLAAC.