Re: [v6ops] How do you solve 3GPP issue if neither operator nor handset supports PD?

Ole Troan <otroan@employees.org> Thu, 26 November 2020 18:32 UTC

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From: Ole Troan <otroan@employees.org>
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Subject: Re: [v6ops] How do you solve 3GPP issue if neither operator nor handset supports PD?
Date: Thu, 26 Nov 2020 19:32:04 +0100
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Cc: ipv6@ietf.org, Michael Richardson <mcr+ietf@sandelman.ca>
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To: Philip Homburg <pch-ipv6-ietf-7@u-1.phicoh.com>
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> On 26 Nov 2020, at 19:11, Philip Homburg <pch-ipv6-ietf-7@u-1.phicoh.com> wrote:
> 
>> Doing this kind of unicast request/response is PRECISELY what DHCPv6
>> was created for.
> 
> I agree. The question is whether it actually good at this.
> 
> DHCPv6 has a very complex model. There can be multiple relays and multiple
> DHCP servers. So a downstream router first has to collect offers and then
> select one.

It’s hard to see what you could remove. A RA solution would likely have to be implemented with some sort of database backend like RADIUS. That something isn’t specified, doesn’t make it simple. 

> 
> DHCP is separate from RA. So coordination is required between DHCP and RA
> if we want to delegate the entire prefix.
> 
> Worse, we have trouble tying a DHCP PD to link state. 

The goal of PD is _not_ to tie it to link state. I would expect that goal to be general regardless of wire-representation. 

> So there is an opportunity to come up with a better way of doing prefix
> delegation.
> 
> RA has the advantage that all information can be in a single RA, ensuring
> consistency. We can also add mechanisms that the downstream node quickly
> and reliably notices flash renumbering independent of link state.

It might be worth noting that  RAs do not guarantee all information in a single RA. It can be split across multiple messages or come from different sources. 

Let’s ask the question differently. Would RS/RA be a good protocol for address assignment?

Cheers 
Ole