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Re: failure detection
El 17/08/2005, a las 18:08, Paul Jakma escribió:
On Wed, 17 Aug 2005, marcelo bagnulo braun wrote:
FWIW, TCP for instance already provide some form of such signaling
see Appendix E.1 of RFC 2461 Of course other ULP don't provide any
kind of feedback.
So i guess it would be a better not to fully rely on ULP feedback,
but otoh not using the information that some ULP provide seems
suboptimal to me.
1. I said "extra signaling"
2. Note the title of appendix E: "IMPLEMENTATION ISSUES" and
describes a possible optimisation that can be made if ULP's can be
modified - it's wholly at the implementation's discretion.
Exploring stuff like path-reachability probing or implementation
optimisations via shim<->ULP signalling (which ULP could be IP quite
likely btw, not TCP - implementations possibly will have /two/ layers
to pass hints through) is fine, but do it as an appendix or an
informational document or wait for implementors to experiment.
I guess i agree, since we cannot be sure that all ULPs will provide
such feedback, we cannot base the shim failure detection on the
existence of such mechanisms, since it would result in limiting the
shim applicability to only those ULPs
The path-probing is, imho, mostly a complete waste of time. But an
implementation can go wild if it wants.
i am not sure what do you mean by this... i mean, if you don't have a
ULP that provides feedback, how can you be sure that the other end is
reachable? i mean, i see probing as a last resource to confirm that an
outage has occurred (and then a tool to explore alternative paths
before diverting the actual data packets)
so, while in multiple occasions it may not be needed and can be
skipped, i see probing as a fundamental part of the shim
The potentials of TCP<->Shim signaling are interesting I'll admit.
However, again it's an implementation detail
may agree with this, but imho it need to be taken into account when
discussing the present topics
(and only reason its being discussed is cause of the crazy
I note from the archives that I'm not the first person to have
cautioned against going down the path-probing route (Joe Abley too).
Paul Jakma firstname.lastname@example.org email@example.com Key ID: 64A2FF6A
Logic is a systematic method of coming to the wrong conclusion