Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)

Victor Kuarsingh <victor@jvknet.com> Mon, 13 November 2017 13:35 UTC

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From: Victor Kuarsingh <victor@jvknet.com>
Date: Mon, 13 Nov 2017 08:35:15 -0500
Message-ID: <CAJc3aaPb8vOxfUVk-6sQNGpftegPCgb+j3OyGD55rmCado+VZw@mail.gmail.com>
Subject: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host)
To: Fernando Gont <fgont@si6networks.com>
Cc: Lorenzo Colitti <lorenzo@google.com>, "6man@ietf.org" <6man@ietf.org>, "v6ops@ietf.org WG" <v6ops@ietf.org>
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On Mon, Nov 13, 2017 at 8:20 AM, Fernando Gont <fgont@si6networks.com>; wrote:
> On 11/13/2017 07:14 PM, Lorenzo Colitti wrote:
>> On Mon, Nov 13, 2017 at 6:21 PM, Fernando Gont <fgont@si6networks.com
>> <mailto:fgont@si6networks.com>> wrote:
>>
>>     >From a operational point of view, one would wonder why pursue this path
>>     as opposed to e.g. do DHCPv6
>>
>>
>> As for DHCPv6 specifically, one reason is that DHCPv6-only networks are
>> not recommended by the IETF. RFC 7934.
>
> Yes, sorry: I meant DHCPv6-PD.
>
> RFC7934:
>
>     Due to the drawbacks imposed by requiring explicit requests for
>     address space (see Section 4), it is RECOMMENDED that the network
>     give the host the ability to use new addresses without requiring
>     explicit requests.  This can be achieved either by allowing the host
>     to form new addresses autonomously (e.g., via SLAAC) or by providing
>     the host with a dedicated /64 prefix.  The prefix MAY be provided
>     using DHCPv6 PD, SLAAC with per-device VLANs, or any other means.
>
> Therefore, why re-invent PD in SLAAC?

PD is quite vast, and this draft describes a specific set of use
cases.  It does not seem like a re-invention of PD in SLACC to me.

>
>
> That aside, same RFC says:
>     Using stateful address assignment (DHCPv6 IA_NA or IA_TA) to provide
>     multiple addresses when the host connects (e.g., the approximately 30
>     addresses that can fit into a single packet) would accommodate
>     current clients, but it sets a limit on the number of addresses
>     available to hosts when they attach and therefore limits the
>     development of future applications.
>
> I seem to recall many systems limit the number of addresses per
> interface to 16.

Current limitations are likely ephemeral and can change over time.

> So the limit of "30 per request" aleady gives you more
> than what you typically get, in practice, with SLAAC. Also... is issuing
> multiple requests forbidden?

I think we also have enough history in computing and the Internet to
know that today's concept of "that is way more then we need, so why do
we need more" is not a good argument to limit capabilities.

regards,

Victor K



>
> Thanks,
> --
> Fernando Gont
> SI6 Networks
> e-mail: fgont@si6networks.com
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
>
>
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