Subject: Re: '::' address as destination

From: Erik Nordmark <[email-masked]>
Date: Sat, 29 Dec 2001 00:56:58 +0100 (CET)

> Hello,
> 
> RFC 2373 states that:
> "The unspecified address must not be used as the destination address
>  of IPv6 packets or in IPv6 Routing Headers."
> 
> However it seems that certain stacks are using this address in a different
> way.

Yes, but I don't think there is an inherent conflict.
RFC 2373 specifies the behavior on the wire i.e. what is carried in
IPv6 packets.
Implementations might do various things at the API interface, but the 
an implementation should ensure and :: doesn't appear as the destination in
the IPv6 packets it sends.

> When '::' is the destination address:
> - some use the first available interface's address
> - some use the loopback address
> 
> Is there a chance that one of these will become the acceptable norm? It
> would be interesting to know if the majority of implementations actually
> return an error for this case.

I know that for Solaris we interpret :: at the API as the loopback
address. This was done to be consistent with the IPv4 Solaris code.
Unfortunately the introduction of the mechanism in the IPv4 Solaris code
was before my time. I don't think it existed in BSD 4.3tahoe but I haven't
checked.

  Erik

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 03 Jan 2002 08:32:28 +0100

Erik,

You are correct of course in terms of the wire protocol. The issue is that
people using heterogeneous systems will be confused by inconsistency between 
implementations.

   Brian