On Fri, Dec 09, 2005 at 01:51:52AM -0500, Matthew J Zekauskas wrote: > Matt Mathis started a discussion around one of the open technical issues > in the draft: how often should you probe to see if the MTU has been raised > along a path. The draft currently says five minutes, but that value > was somewhat arbitrary. Matt wondered if anyone has insights into > existing precedent or a rational way of picking a number. > Michael Richardson thought 5 minutes sounded about right, and in > any case it should be greater than the 2 minute TCP timeout; he > also thought it should not be larger than the typical damping interval > for BGP. John Heffner commented that ten minutes is commonly used for > values in route caches. Fernando Gont suggested a strategy being considered > for OpenBSD: base the probe interval based on the current MTU size. If the > size is small, probe more frequently; if the value is large (and still > working) use a larger timeout. Matt asked if Fernando considered 1500 > large or small. Fernando thought "small", and a "large" value might > be something greater than 6000 right now; a value of 10 to 15 minutes > might be appropriate there. Dave Thalor noted that since the draft > is an extension of "PMTUD classic" right now, RFC 1981 says 10 minutes, > so that's a value that you would not have to defend.
What about specifying a bitrate by considering all probes lost. So
PMTUd-new shouldnt sent out more than 100 bit/s additional traffic.
Which makes it 2 Minutes for 1500 byte probes. (1500 * 8 / 120)
Flo
--
Florian Lohoff [EMAIL PROTECTED] +49-171-2280134
Heisenberg may have been here.
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