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

Ted Lemon <mellon@fugue.com> Sat, 18 October 2014 12:57 UTC

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From: Ted Lemon <mellon@fugue.com>
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To: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Cc: HOMENET Working Group <homenet@ietf.org>, James Woodyatt <jhw@nestlabs.com>
Subject: Re: [homenet] Let's make in-home ULA presence a MUST !?
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On Oct 17, 2014, at 11:25 PM, Brian E Carpenter <brian.e.carpenter@gmail.com> wrote:
>> I did explain how to do that: before the network partitions, 
> 
> That seems to imply that you know in advance that the network
> will partition. I assume that it will usually be a surprise.
> Normally there is no human manager, although a human might
> randomly disconnect cables or switch off a power socket.
> 
> So I think you mean: as soon as the network has generated its ULA...

That is indeed what I meant, sorry for not saying so explicitly.

>> divide the ULA into 64k /64 prefixes, and distribute these evenly among attached routers.
> 
> ...but that will break when another router attaches itself later,
> unless the (re)distribution process is continuous.

Which is the reason we have HNCP.

>> Routers other than the ones that own a particular /64 are not allowed ever to use that /64 unless the router that owns it relinquishes it to them explicitly.
> 
> Sure, and this needs to be supported by HNCP (or something else).

Yup.

>>  Prior to partition, an agreement is made that one of the routers gets to keep the ULA in the event of a long-term partition. 
> 
> Again: that has to happen as soon as the ULA is generated, since partition
> is unpredictable.

To clarify, yes, when the ULA is generated you have to do this, but you may revisit the decision subsequently, prior to partition.   You don't know when partition happens, but that doesn't preclude making new choices later.   E.g., if you only have one internet connection, you might want the device connected to that link to be the one that holds the token.   Or you may have a dedicated server on-link which would be ideal for stuff like this, although we really haven't talked about non-router servers participating in HNCP.