Re: [homenet] Let's make in-home ULA presence a MUST !?

Ted Lemon <> Mon, 20 October 2014 19:34 UTC

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From: Ted Lemon <>
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Date: Mon, 20 Oct 2014 15:34:32 -0400
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Subject: Re: [homenet] Let's make in-home ULA presence a MUST !?
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On Oct 20, 2014, at 2:00 PM, James Woodyatt <> wrote:
> Okay... except it seems you're admitting that my scenario where a simple reconfiguration of a network topology, e.g. one caused by an intermittent RF interference on an unlicensed band of the radio spectrum, would result in a fully regular and normalized generation of a ULA prefix that would subsequently be deprecated on network rejoin and subsequently deprecated again. This could happen several times per hour, right?

No, if it's done right the network would have to be partitioned for on the order of a week or two before the new ULA would be generated.

>>> > Returning to my question: why do we always need a locally-generated ULA prefix?  If it's to provide a time-invariant locally routable address to hosts, then locally generated ULA prefixes cannot ever be permitted to expire for any reason.  If they are ever allowed to expire, then they don't provide the time-invariant property.  However, if we don't actually need the time-invariant property, then what does a locally-generated ULA prefix do for us whenever one or more delegated prefixes is also present? It's not clear to me they are anything but absolutely redundant and unnecessary in that situation.
>> This is a bit of a straw man (see previous comment).   I think trying to keep a permanent ULA is a good thing.   We can't always succeed, but we can make the set of circumstances under which we fail as small as possible.   This is in contrast to what you are proposing, which is that we essentially set out to fail, and see deprecation events whenever the upstream network goes down.
> I certainly would agree with your observation that I don't see keeping a permanent ULA as a good thing in itself. I keep asking why that would be beneficial, and the answers continue to leave me scratching my head. Please count me as one of the people here who has read Brian Carpenter's rant in SIGCOMM about IP Addresses Considered Harmful, and who generally agrees. I'm uncomfortable trying too hard to achieve some partial and dubious success at establishing a persistent ULA prefix in the home network. I think we should put our efforts more into making persistent the local namespace for service registration and discovery.

The reason I think it's beneficial is that it reduces to the minimum the number of instances where a long-lived connection will have to be broken because of a renumbering event.   I don't think we can reduce that number to zero, but I think we can make it a lot less likely than it would be if we renumber every time the upstream link goes away.