Steve/Brian -
You've probably seen Mick Seaman's comments on this by now - as he points
out in his email, tinkering with existing STP implementations is not likely
to be a rewarding exercise and I would encourage you not to go there.
I would suggest that it would be a much more valuable exercise for the
Linux community to replace the existing STP support with an implementation
of RSTP.
Regards,
Tony
At 02:06 14/09/2006, Stephen Hemminger wrote:
On Wed, 13 Sep 2006 15:58:49 -0700
Brian Braunstein <[EMAIL PROTECTED]> wrote:
> hi stephen and tony,
>
> i have been in contact with both of you and i figured it would make
> sense to get you to in contact on this issue, so here's the story:
>
> stephen is the maintainer of the linux spanning tree bridging code, an
> implementation of 802.1D-1998 that has very wide spread use.
>
> tony is the chair of the IEEE802.1 working group.
>
> i am trying to get my patch submitted in the linux kernel to fix a bug
> in the way STP behaves. stephen and i discovered that the flaw is
> actually in the IEEE802.1D-1998 spec, and that the linux implementation
> was merely following this. i contacted tony to try to see if we can get
> an update to the 802.1D-1998 spec, as this is what is implemented in the
> linux kernel, but tony said that the 1998 standard is obsolete, will not
> be updated, and that the 2004 RSTP spec should be used.
>
> so here's a review of what i've come across:
>
> first lets start with the bug in the 802.1D-1998 spec
>
> 1998 - 8.6.2.2 Record Configuration Information - Use
> you will notice that if the path cost ever goes up and everything
> else is held constant, the BPDU will be dropped and the network not
> react to the change, and the dropping of the BPDUs will make it seem
> like the link is down.
>
> now lets look at the equivalent section in the 8021.D-2004 spec:
>
> 2004 - 17.6 Priority vector calculations
>
> as you can see here, this bug has been fixed, because the last
> condition takes care of the problem, if the config message is received
> from the same designated bridge and designated port, then the config
> message is processed. so path cost increases will be recorded and
> reacted to.
>
>
> the issue is whether or not the linux kernel should go with the 1998 or
> 2004 spec. i would assume that the goal is to make the linux
> implmentation a functional implementation of the original STP, not a
> complete rewrite to conform to all of RSTP, so lets look at what the new
> standard says for normal legacy STP, to see if the bug is fixed there as
> well:
>
> 2004 - 17.4 STP compatibility
>
> this section seems to say that an RSTP bridge will revert to STP as
> defined in section 8. so then we go to section 8...
>
> 2004 - 8 Spanning tree algorithm protocol
>
> this one then refers to 802.1D-1998 for the STP spec, but also says
> that it is obsolete and RSTP should be used
>
> so this is a bit confusing. section 17.4 says use STP to interoperate
> with legacy bridges, then section 8 either says use the 1998 spec, or
> don't use STP at all, but if bugs in the 1998 spec cannot be correct,
> what are we to do with the linux code? i can write the patch to
> implement the new algorithm from 2004-17.6 to replace the algorithm from
> 1998-8.6.2.2.
>
> thanks for you help guys,
> hopefully we can get this bug fixed up soon, you both have been great
> about timely responses and it is much appreciated.
>
> Brian Braunstein
> 858.245.0434
I have no problem fixing the code to be spec noncompliant, there
are several case where we implement the "right thing" rather than
the "standard way". I just want to make sure any such changes don't
have unintended consequences.
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
