Subject: Re: RE: RE: Prefix Delegation using ICMPv6

From: <[email-masked]>
Date: Tue, 22 Aug 2006 22:48:49 -0500 (CDT)

>From: "Durand, Alain" <[email-masked]>
>Date: 2006/08/22 Tue PM 10:31:10 CDT
>To: [email-masked], Syam Madanapalli <[email-masked]>, 
	IETF IPv6 Mailing List <[email-masked]>
>Subject: RE: RE: Prefix Delegation using ICMPv6

> 
>> Thanks for the quick e-mail. As one of the co-authors, I'd in 
>> turn like to reply (and state that ICMPv6 PD is ANOTHER way 
>> to do IPv6 PD, NOT a replacement for the existing mechanism). 
>> FWIW, please see comments in-line:
>
>This is probably the crux of the issue.
...
>I believe that having multiple IETF standardized ways to achieve the same thing is a bad idea.

Hi Alain, I respect your opinion but believe differently. BTW, there is already at least one such instance of their being "multiple IETF standardized ways to achieve" IPv6 addressing for nodes. SLAAC (RFC 2462[bis]) and DHCPv6 (RFC 3315), AND DHCPv6 'lite' (RFC 3736).

Tim
Rom 8:28

>   - Alain.

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From: Ralph Droms <[email-masked]>
Date: Wed, 23 Aug 2006 00:04:04 -0400

Tim - SLAAC and DHCPv6 are fundamentally different ways to assign  
addresses.  Don't forget manual assignment, as well.  DHCPv6 for  
other information (RFC 3736) has nothing to do with addressing.

I would be interested in seeing more detail about specific topologies  
and scenarios in which DHCPv6 PD is inadequate.  All I've seen in a  
quick read of your doc is the argument that some hosts may not  
implement DHCPv6, so there is a need for some way to accomplish PD  
without DHCPv6.  But I think Alain refuted that argument by pointing  
out that any new PD protocol would also, by definition, not be  
implemented already in any hosts, so the advantage is minimal.

We had a long discussion about PD alternatives some time before the  
DHCPv6 PD RFC was published.  The consensus was, at that time, that  
the protocol messages and amount of "work" required for PD was pretty  
much the same regardless of how the messages are carried (DHCP, ICMP,  
etc.), and there was also consensus that PD seemed a logical  
extension of the address assignment in DHCP, so that consensus was  
the motivation for DHCPv6 PD.

- Ralph

On Aug 22, 2006, at 11:48 PM, <[email-masked]> wrote:

> Hi Alain, I respect your opinion but believe differently. BTW,  
> there is already at least one such instance of their being  
> "multiple IETF standardized ways to achieve" IPv6 addressing for  
> nodes. SLAAC (RFC 2462[bis]) and DHCPv6 (RFC 3315), AND DHCPv6  
> 'lite' (RFC 3736).
>
> Tim
> Rom 8:28
>
>>
>>   - Alain.
>
>

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 23 Aug 2006 10:09:42 +0200

[email-masked] wrote:
> Hi Alain, I respect your opinion but believe differently. 

However, Alain is only citing a design principle that we often use when
deciding whether a new idea is valuable. You'll find it in RFC 1958:

    3.2 If there are several ways of doing the same thing, choose one.
    If a previous design, in the Internet context or elsewhere, has
    successfully solved the same problem, choose the same solution unless
    there is a good technical reason not to.  Duplication of the same
    protocol functionality should be avoided as far as possible, without
    of course using this argument to reject improvements.

but it certainly wasn't original then. In other words, you have to
supply "a good technical reason" to add new functions. Given that
DHCP has become pretty much universal in IPv4 deployment, I'm having
a hard time seeing why the same won't happen for IPv6.

      Brian

> BTW, there is already at least one such instance of their being "multiple IETF standardized ways to achieve" IPv6 addressing for nodes. SLAAC (RFC 2462[bis]) and DHCPv6 (RFC 3315), AND DHCPv6 'lite' (RFC 3736).
> 
> Tim
> Rom 8:28
> 
> 
>>  - Alain.
> 
> 
>