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Re: [PLUG] DNS Problem Now
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On Monday, October 21, 2002, at 08:38 PM, Bill Jonas wrote:
On Mon, Oct 21, 2002 at 07:08:02PM -0400, Paul wrote:
What would cause *all* DNS servers to have extremely long response
times?
Well, the closeness of the IP addresses made me suspect that the two
machines are on the same network segment. A traceroute confirmed this:
$ traceroute -f18 207.172.3.8
traceroute to 207.172.3.8 (207.172.3.8), 30 hops max, 38 byte packets
18 ge4-0.core2.lnh.md.rcn.net (207.172.15.18) 324.034 ms 325.896 ms
329.332 ms
19 pos5-0-0.core3.mrf.va.rcn.net (207.96.92.130) 338.086 ms 354.696
ms 355.453 ms
20 ge5-0-0.sys-core1a.mrf.va.rcn.net (208.59.255.85) 327.046 ms
336.568 ms 334.854 ms
21 corky.dns.rcn.net (207.172.3.141) 318.522 ms 338.460 ms 331.926
ms
$ traceroute -f18 207.172.3.9
traceroute to 207.172.3.9 (207.172.3.9), 30 hops max, 38 byte packets
18 ge4-0.core2.lnh.md.rcn.net (207.172.15.18) 350.408 ms 360.328 ms
320.479 ms
19 pos0-0-0.core3.mrf.va.rcn.net (208.59.94.74) 312.727 ms 327.534
ms 318.653 ms
20 ge5-0-0.sys-core1a.mrf.va.rcn.net (208.59.255.85) 317.359 ms
364.770 ms 336.711 ms
21 hellboy.dns.rcn.net (207.172.3.140) 352.516 ms 342.263 ms
352.258 ms
This, combined with the non-responsiveness to pings, suggests that they
were simply unreachable or experiencing packet loss during the time
period you had trouble with them. Either that, or they're simply the
same machine, which might suggest that it was experiencing heavy load
during the time in question.
Bill's traceroute points out a problem that I see more and more
frequently all around the net these days... INCREDIBLY HUGE hop-counts.
Hop-counts have been steadily increasing around the net for years, so
this kind of hop-count is actually pretty "normal" these days. But
while hop-counts in and of themselves are not a significant issue, the
fact is that they put that many more places for congestion to occur
between you and your destination... and the current IP default is 30
hops! (It used to be 10.)
The roundtrip times indicate that significant congestion is probably
occurring on the network involved. The Internet is surprisingly
robust... but it does get overloaded frequently... especially the
further away you get from the backbone carriers on to various
sub-carriers. Topology is the name of the game.
T.T.F.N.
William H. Magill
magill@mcgillsociety.org
magill@acm.org
magill@mac.com
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