Subject: Re: [homenet] HNCP, RA and DHCPv4

From: Steven Barth <[email-masked]>
Date: Sat, 01 Aug 2015 09:25:46 +0200

>This is why I think it would be great if the deprecated prefix
>continued to be sent (in RA and HNCP) until its original valid lifetime
>expired. 

The problem is that the valid lifetime can be several years so I don't think that is very practical unless we want to also enforce an upper bound on announced lifetimes which is starting to feel a bit uncomfortable. That's why I think an upper limit like the 2h makes sense.

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From: Juliusz Chroboczek <[email-masked]>
Date: Sat, 01 Aug 2015 11:56:52 +0200

> The problem is that the valid lifetime can be several years

Huh?  The HNCP implementation controls the valid lifetime it sends, why
would it set it to several years?

(But point taken about not sending too many zero-lifetime RAs after
multiple episodes of renumbering.)

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From: Juliusz Chroboczek <[email-masked]>
Date: Sat, 01 Aug 2015 12:02:18 +0200

> After that you can also include the PIO with PL=VL=0 in the periodic
> RAs (that you'll presumably be transmitting anyway)

How many PIOs will fit?  Is the 1280 octet minimal MTU the only limitation?

-- Juliusz

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From: Juliusz Chroboczek <[email-masked]>
Date: Sat, 01 Aug 2015 12:07:30 +0200

> For all intents and purposes a "deprecated" prefix is one with a preferred
> lifetime of 0 so that is supported (TLV has valid and preferred lifetimes).
> If your ISP does a graceful renumbering than that is what happens, your
> RA server just has to play ball here though.

Right, I was wondering what those fields in the Delegated Prefix TLV are
for, now I know.

I don't see anything on this subject in the "Applying Assignments"
section.  Have I missed something?

>> FORCERENEW with Nonce authentication might also be helpful, I'm not
>> sure.

> Nobody (I know) implements that, though.

I haven't tested, but unless I've misunderstood Roy, dhcpcd does.

-- Juliusz

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From: Tore Anderson <[email-masked]>
Date: Sun, 2 Aug 2015 11:08:49 +0200

* Juliusz Chroboczek

> How many PIOs will fit?  Is the 1280 octet minimal MTU the only

I don't think there's any practical limit, considering that you can
simply send multiple RAs if necessary. RFC 4861, section 6.2.3:

   If including all options causes the size of an advertisement to
   exceed the link MTU, multiple advertisements can be sent, each
   containing a subset of the options.

(I'm not saying that I think doing so for a ton of withdrawn prefixes
for several weeks or months would be a good idea or anything, but is
technically possible.)

Tore

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From: Mikael Abrahamsson <[email-masked]>
Date: Wed, 5 Aug 2015 12:12:00 +0200 (CEST)

On Mon, 27 Jul 2015, Juliusz Chroboczek wrote:

> During my quick talk on Wednesday, I mentioned that I had been pleasantly
> surprised at the very clean interaction between the protocols:
>
>  - HNCP redistributes assigned prefixes into the routing protocol;

I was under the impression that HNCP/hnetd configured address+prefix on 
interfaces which is then picked up by the routing protocol when it looks 
at what addresses/prefixes are available on what interfaces. Am I wrong?

-- 
Mikael Abrahamsson    email: [email-masked]

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From: Steven Barth <[email-masked]>
Date: Wed, 5 Aug 2015 12:17:27 +0200

Am 05.08.2015 um 12:12 schrieb Mikael Abrahamsson:
> I was under the impression that HNCP/hnetd configured address+prefix on interfaces which is then picked up by the routing protocol when it looks at what addresses/prefixes are available on what interfaces. Am I wrong?

No, you aren't.