Re: SLAAC vs DHCPv6 (Re: RFC4941bis: consequences of many addresses for the network)

[Fernando Gont <[e-mail]>]

On 27/1/20 20:36, Brian E Carpenter wrote:
> On 28-Jan-20 10:44, Fernando Gont wrote:
>> On 26/1/20 17:47, Brian E Carpenter wrote:
>>> On 27-Jan-20 09:22, Simon Hobson wrote:
>>>> Gyan Mishra <[e-mail]> wrote:
>>>>
>>>>> The beauty behind SLAAC is that it works “out of the box” PNP like features makes it very user friendly to initiatally deploy.
>>>>
>>>> Remember that DHCP for IPv4 generally works "out of the box" for most users. Certainly in the SOHO market, the presence of a built in, auto-configured, and enabled DHCP server in the route means that the user just "plugs it in and it works". By the time you get to a level of network complexity where that isn't the case, then there is normally a network admin either on the staff or hired n as needed.
>>>>
>>>> If that isn't working reliably for users in the IPv6 world then that suggests the various components needed haven't reached the same level of completeness & correctness "mostly" available in the IPv4 world. It isn't an argument that DHCPv6 "doesn't work".
>>>
>>> It's actually a historical accident. At the time that SLAAC was designed, DHCP(v4) wasn't mature and the state of the art in autoconfiguration was Appletalk, Novell IPX, and DECnet Phase IV. It really doesn't matter now. We can't roll the clock back.
>>
>> Well, we *could* end the pointless religious battle, mandate both SLAAC
>> and DHCPv6, and let admins and operators run their networks in whatever
>> way they please.
> 
> That still doesn't resolve the issue of the lack of feature equivalence between RAs and DHCPv6,

Indeed. At the very least, one would have a DHCPv6 route option.

So far, IIRC the arguments against this have been that a DHCPv6 server 
couldn't be ain a good position to tell where packets should be routed. 
However, a number of proposals recently discussed in this working group 
have failed that criteria (if it ever existed).

Folks that need/want to "enforce" policy, should be able to do so. 
Besides, they should be able to rely on any automatic configuration 
mechanism rather than having to duplicate the effort in both protocols.

e,g,-, My ISPs CPE does network configuration (addresses `other info) 
with both SLAAC and DHCPv6 -- because they have to make sure it works 
with whatever stuff their users plug.

Part of the outcome is that while my box does rfc7217+rfc4941, I also 
configure dhcpv6 addresses, and the dhcpv6 server generates IIDs in a 
predictable manner.


> and there would some interesting discussions around which options need to be MTI. For example, is 
 > PD mandatory to implement? It would be interesting to see a draft 
(v6ops, perhaps?). However, I imagine that the constrained node people 
would have something to say if we changed this to a MUST:
> 
> "...all hosts SHOULD implement address configuration via DHCPv6." [RFC8504, section 6.5]

My understanding is that the constrained node folks already have to 
deviate a bit from plain IPv6. So I guess that could be worked out.

It would seem to me the problem here is more of Android than anything else.


-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492