Hello Pekka,

Thank you for the response.

On Tue, 2008-10-28 at 08:07 +0200, Pekka Savola wrote:
> On Tue, 28 Oct 2008, Chan-Wah Ng wrote:
> > We have written a draft on the formation of tunnel loops, and possible
> > approaches on loop detection.
> >
> > As it is a general problem for tunneling protocols, the draft was
> > written for intarea.  However, there has been recent discussions on the
> > Mobility Extension WG on the HA loop threat, and even more recently in
> > 3GPP CT1.  Hence, this announcement is cross-posted to Mext as well.
> >
> > We would like to solicit for comments on the draft, and suggestions on
> > possible way forward.
> 
> As you point out, IPv6 tunnel spec already has tunnel encapsulation 
> limit, which you point out, could be even better.  But my concern is 
> how much this is a problem in practise.  Among those IPv6 tunnel 
> implementations I've looked at, none of them implemented tunnel 
> encapsulation limit.  I wonder -- if they didn't bother to implement 
> that, what would make them to bother implement this?
> 
AFAIK, Linux has always implemented the TEL option
in /net/ipv6/ip6_tunnel.c since the early 2.6.0 days.

In any case, a lack of implementation should not be used as an argument
against a possible fix to the problem -- especially if it is IPv6 we are
talking about (which is still far from being as pervasive as it should
be). 

As to whether there is a practical need to fix this problem, it is up to
the IETF community to decide. The information I can provide to help make
that decision is both Mext WG and 3GPP CT1 has acknowledged it as a
problem.

/rgds
/cwng

> It appears there was a -00 I-D in IPng WG in 2002, which the probable 
> intent of getting the IPv6 tunnel spec to draft standard, but the work 
> dried up.
> 
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