----- Original Message -----
From: "Loa Andersson" <loa(_at_)pi(_dot_)nu>
To: <mark(_dot_)tinka(_at_)seacom(_dot_)mu>; <stbryant(_at_)cisco(_dot_)com>
Cc: <gorry(_at_)erg(_dot_)abdn(_dot_)ac(_dot_)uk>; <mpls(_at_)ietf(_dot_)org>;
<ietf(_at_)ietf(_dot_)org>;
<david(_dot_)black(_at_)emc(_dot_)com>; <tsvwg(_at_)ietf(_dot_)org>;
<jnc(_at_)mit(_dot_)edu>; <lisp(_at_)ietf(_dot_)org>
Sent: Thursday, January 09, 2014 4:16 PM
Changed the subject line !
<trimmed the distribution>
On 2014-01-09 20:36, Mark Tinka wrote:
On Thursday, January 09, 2014 02:08:43 PM Stewart Bryant
wrote:
Either or both.
I can only speak to native MPLS, as I've never run tunneled
MPLS.
I am interested in how often in practice MPLS packets get
misdelivered due to label corruption.
Well, first of all, routers would need to report corrupted
MPLS frames so operators can glean this data. This isn't
something I've come across, but it would be good to find
some kind of way to count this across interfaces, if the
routers can detect and report them.
This would be possible to do with MPLS-TP OAM, wouldn't it?
I think not. There was a lot of discussion back in 2008/2009 on the
MPLS-TP list about the loss of source address information in MPLS and
how that could be fixed in MPLS but AFAIK nothing was done about it.
At the time, it was misconfiguration defects that were the motivation -
a packet arrives at the wrong place but how on earth can you tell who
sent it and so tell them about it? - but an MPLS label corrupted in
transit would do just as well.
At the same time, I remember well the nervousness of switching from X.25
to Frame Relay, where the assumption was that links were so reliable
that error detection and recovery could safely be left to the higher
layers, that it was no longer needed at the link layer. That
nervousness seems not to have been justified; perhaps it is not now.
Tom Petch
/Loa
The known issue about mis-delivery of MPLS frames is poorly-
sized MTU interfaces. I have no empirical data as to how
this can corrupt successive MPLS frames that may fit into
the transit MTU. But in this case, as with any Layer 2
traffic, not enough MTU = dropped frame.
Mark.
--
Loa Andersson email:
loa(_at_)mail01(_dot_)huawei(_dot_)com
Senior MPLS Expert loa(_at_)pi(_dot_)nu
Huawei Technologies (consultant) phone: +46 739 81 21 64