Subject: Re: Usability enhancement for IP6
To: Bryan Phillippe <>
From: Fernando Gont <>
List: tech-net
Date: 02/06/2005 07:27:42
At 11:06 05/02/2005 -0800, Bryan Phillippe wrote:

>Ever since I configured a private IPv6 network with NetBSD, I've had the
>annoying problem of having to wait for multiple failed retransmits to
>public sites such as, before falling down to IPv4.  Other
>IPv6 stacks, such as Microsoft, do not have this problem.
>The following small patch fixes the problem for me: IPv6 connections to
>other private IPv6 hosts work fine and IPv6 connections to unreachable
>public IPv6 hosts fail immediately and fall back to IPv4.

This has been the subject of an Internet-draft I submitted to the IETF back 
in July 2004. You can visit . There you'll find the 
latest version of the draft, plus links to the minutes and slides of the 
relevant IETF meetings.

Unfortunately, I'm not sure we have reached consensus at the relevant IETF 
working group (tcpm).

If you would like this behaviour to become a recommended practice, please 
drop a line on the TCPM WG mailing list, or do it here and I'll forward it 

Does anyone know if this patch will be included in the next releases of NetBSD?

>+       * If connection hasn't completed, and either gets a "host/net
>+       * unreachable" or has retransmitted several times and receives a
>+       * second error, give up now.  This is better than waiting a long
>+       * time to establish a connection that can never complete.
>         */

Remove the "and receives a second error".

Best regards,

Fernando Gont
e-mail: ||