Subject: RE: [mpls] draft-ietf-mpls-icmp-08.txt

From: <[email-masked]>
Date: Thu, 8 Feb 2007 08:04:24 -0000

Ron/Stewart,

The real problem here is that we are not always clear about which layer
network are are talking about.  ICMP is part of the IP layer network's
(and ONLY the IP layer network's) management-plane.  When layer networks
get functionally coupled then folks are tempted to devise clever ways to
use the protocols that belong to one layer network in/by another layer
network....but this is really not a good general idea (this is
especially true if the layer networks involved belong to different
network modes).

The consequence of functionally coupling different layer networks is
almost always practically manifested as increased complexity and
increased marginal cost, ie one ends up with diseconomies of
scale....though it usually takes significant deployment to see this to
really figure-out what the real cause is (though it is my experience
most folks don't even see this anyway).

regards, Neil

> -----Original Message-----
> From: Ron Bonica [mailto:[email-masked]] 
> Sent: 07 February 2007 20:37
> To: Stewart Bryant
> Cc: [email-masked]; pwe3
> Subject: Re: [mpls] draft-ietf-mpls-icmp-08.txt
> 
> 
> Hi Stewart,
> 
> As currently defined, the ICMP message is a response to the 
> unroutable IP datagram. In an application like pseudowires, 
> you wouldn't send an ICMP packet.
> 
> However, now that ICMP messages are extensible, people might 
> find new applications form them. But let's say that this is 
> beyond the scope of this draft and fair game for future drafts.
> 
>                                      Ron
> 
> Stewart Bryant wrote:
> > This draft explains what to do if you have
> > IP over MPLS, but not what to do if you
> > are carrying something other than IP - for
> > example a pseudowire.
> > 
> > It occurs to me that in some cases it would
> > be useful to resolve the MPLS destination
> > label to the destination IP address, and
> > send the diagnostic packet forward.
> > 
> > Clearly that does not work if you have
> > an unknown label or an unknown next hop,
> > but there may be other circumstances where it
> > is useful.
> > 
> > - Stewart
> > 
> > 
> > 
> > 
> > 
> > _______________________________________________
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> > [email-masked] https://www1.ietf.org/mailman/listinfo/mpls
> > 
> 
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