Subject: draft-ietf-v6ops-addr-select-ps-02

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 3 Dec 2007 14:11:20 -0800

I'm reading draft-ietf-v6ops-addr-select-ps-02 and I found something  
that I find somewhat troublesome:

2.2.1. IPv4 or IPv6 prioritization The default policy table gives IPv6  
addresses higher precedence than IPv4 addresses. There seem to be many  
cases, however, where network administrators want to control the  
address selection policy of end- hosts the other way around.

I have a hard time believing this is true. Why would anyone want to  
enable IPv6 and then leave it unused? And if it is true, it's highly  
problematic: if IPv6 capability is available but not used, this means  
that problems (that are common when deploying new technologies) will  
remain unseen and therefore unfixed.

---

From: Arifumi Matsumoto <[email-masked]>
Date: Wed, 05 Dec 2007 09:03:33 +0900

Hi,
thank you for your comment.

Iljitsch van Beijnum wrote:
> cases, however, where network administrators want to control the address 
> selection policy of end- hosts the other way around.
> 

We've found some operational reasons for IPv6-IPv4 priority control.

- As mentioned some time before at this ML, smooth and conservative
  IPv4 to IPv6 transition might be one reason.

  The transition looks like:
   IPv4 only network,
    -> IPv4 and IPv6 network with IPv4 prioritized.
     -> IPv4 and IPv6 network with IPv6 prioritized.
      -> IPv6 only network

- Another case might be like you have temporariliy extremely poor IPv6
  access line and want to use that only when connecting to IPv6-only
  host.

However, I agree that a new technology, such as IPv6, should be
generally prioritized than the old one.