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Re: [mpls] draft-ietf-mpls-in-udp was RE: gre-in-udp draft (was: RE: [tsvwg] Milestones changed for tsvwg WG)

2014-01-14 10:15:22
Lloyd

I have just read the Stone paper and I have some significant
concerns about its validity with modern h/w. Certainly it
is hard to credit the notion that the  error rate
is in the range 1:1000 to 1:32000 as reported by the authors.

The paper was written in 2000 with hardware that would have
have been designed in the mid 1990s. In that era, h/w was
far more marginal, with performance traded against signal
integrity, and indeed a lot less signal integrity measurement
and simulation took place at both board and chip level. This
was also the era where metastability was just beginning to
become widely understood, and its lack of understanding
would be a possible source of DMA errors.

I therefore do not think we should place much reliance
on this paper, but should instead look at the rather more
modern statistics.

Such statistics ought to be readily available by looking at
the tcp/udp c/s error stats in hosts and routers. As a tiny
and perhaps erroneous sample I looked at three Macs
in the office here and the tcp c/s error stats were
313/29144518, 0/3000000, 0/5000000. Only one of those
three systems got within a factor of 3 of the lowest error
rate reported by Stone.

Bottom line, it seems that we could use more recent data
and then an understanding of how important these low
background error rates are in the tunneling application that
we are considering here.

- Stewart










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