DHCPv6 PD route injection (was: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host))

Ole Troan <otroan@employees.org> Tue, 14 November 2017 00:58 UTC

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From: Ole Troan <otroan@employees.org>
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Subject: DHCPv6 PD route injection (was: Re: [v6ops] Stateful SLAAC (draft-ietf-v6ops-unique-ipv6-prefix-per-host))
Date: Tue, 14 Nov 2017 08:57:33 +0800
In-Reply-To: <CAO42Z2xqwRH94dw=XJf5mt3STdDcTYmB_i1NbXP46shdJQeaPA@mail.gmail.com>
Cc: Lorenzo Colitti <lorenzo@google.com>, Fernando Gont <fgont@si6networks.com>, "v6ops@ietf.org WG" <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>, "Van De Velde, Gunter (Nokia - BE/Antwerp)" <gunter.van_de_velde@nokia.com>
To: Mark Smith <markzzzsmith@gmail.com>
References: <be9724f5-2ff5-d90c-2749-ecae2c628b78@si6networks.com> <CAKD1Yr0_a2Qm8U4oK+BQU57DeDUD9i-o_+G+YhnH4pVXRxmxxQ@mail.gmail.com> <9d154133-a1de-7774-1589-c7069bf279ee@si6networks.com> <0b45890d-ea4a-47b8-a650-ceb72b066df8@gmail.com> <ea772bfd-4004-7f94-8469-b50e3aff0f29@si6networks.com> <F2330138-6842-4C38-B5A0-FB40BFACD038@employees.org> <e40697ca-8017-c9d2-c25d-89087046c9cf@gmail.com> <207f040a-7fe2-9434-e7a5-f546b26fdf63@strayalpha.com> <CAKD1Yr26NK2osApYZBm8Yd=0X7xcetrxojp6=JHOEAu9BB0q8A@mail.gmail.com> <8ca59610-2d25-2be4-9d2c-9b1a75fd3ace@si6networks.com> <E67105A3-396B-403C-B741-E9E01CFB5CE7@employees.org> <862687c9-c107-53a8-288a-29049097b0e1@acm.org> <AM5PR0701MB2836C00EA1AAC73E7E63F583E02B0@AM5PR0701MB2836.eurprd07.prod.outlook.com> <CAO42Z2xacRco7ne7biQ93so0k-x4xSnM2jzoB13-sdVRLshQDQ@mail.gmail.com> <CAKD1Yr0Zz6Jxg_ZuEbBkMhBdEaZKOrtx-eUns7KWi9v-5PDBzg@mail.gmail.com> <CAO42Z2xqwRH94dw=XJf5mt3STdDcTYmB_i1NbXP46shdJQeaPA@mail.gmail.com>
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> On 14 Nov 2017, at 03:43, Mark Smith <markzzzsmith@gmail.com>; wrote:
> 
> 
> DHCPv6 has been designed to avoid having state in intermediary devices
> by incorporating a relay agent into the architecture, specified in
> RFC3315.
> 
> Clients use DUIDs to identify themselves, and the DHCPv6 server
> associates client attributes with the client's DUID. That is what
> allows DHCPv6-PD to survive a router/DHCPv6 relay reboot.
> 
> This draft hasn't been published as an RFC, however it is also
> considering this issue.
> 
> "DHCPv6 Relay Agent Assignment Notification (RAAN) Option"
> https://tools.ietf.org/html/draft-ietf-dhc-dhcpv6-agentopt-delegate-03
> 
> A number of vendors seem to have implemented the functional equivalent
> by looking directly at the ID_PD option when the DHCPv6 reply is sent
> to the client - search for "DHCPv6 Relay Agent Notification for Prefix
> Delegation"
> 
> The alternative is to have a RADIUS server provide the delegated
> prefix information to a DHCPv6 server running on the router. "RADIUS
> Delegated-IPv6-Prefix Attribute", RFC4818.
> 
> Possibly the RADIUS method could be used in this draft's scenario if a
> layer 2 attribute such as the MAC address or per-client VLAN tags, or
> 802.1X authentication information, is used to identify the client.
> 
> If this draft can't document that method because it doesn't exist,
> then, assuming Comcast is the only deployment of this, it seems
> Comcast aren't trying to have a prefix assignment survive a router
> reboot. That's a "flash renumbering" approach, which I don't think is
> right for IPv6.
> 
> 
>> This has not stopped the deployment of tens or hundreds of millions of
>> networks that use DHCPv6 PD.
>> 
> 
> What was the alternative that didn't have this limitation?
> 
> There is a big difference between something working and something working well.

Yes, it's quite unfortunate that we haven't solved the problem of robust route injection in PD yet.

Ralph and I when writing 3633, concluded while there were many options, few of them were attractive, and instead resorted to specify that PD must operate without relays.

Markus enumerated the options here:
https://www.ietf.org/archive/id/draft-stenberg-pd-route-maintenance-00.txt

Let me know if you are interested in working on the problem.

Best regards,
Ole