20030627: HDS feed to/from seistan (cont.)

>From: Robert Leche <address@hidden>
>Organization: LSU
>Keywords: 200306161954.h5GJs2Ld016710 LDM-6 IDD

Hi Bob,

>take a look at the following two cases. Notice the LSU to ULM hop is
>via the network address translation firewall:
>dynip422.nat.ulm.edu.(Line 6) Interestingly, ULM does not pass through
>the same NAT/firewall process. I beleive this could offer a clue.
>The traceroute report is missing the last 3 hops and untill the firewall at
>ULM is opened allow you to ping tornado we will not have a complete picture.

I don't think that this has anything to do with the feed problems we
were seeing from LSU to others.  It only explains the inability to do
complete traceroutes to ULM.  This is/was not part of the feed problems
we have been seeing.

>Some how two different paths are connecting ULM. And this suggests a
>reason why it takes more time to issue packets from Seistan to
>Torando.

It does not explain the asymmetry in feed to/from UCAR.  ULM has been
out of the picture as far as high volume data feeds from seistan for
well over a week now.  Ever since I switched them to feed from
CU/CIRES (rainbow.al.noaa.gov), their HDS latencies have been at or
very near zero.

Now, back to the problem at hand.  Something significant changed yesterday
night:

- the HDS latencies from seistan to zero.unidata.ucar.edu dropped to
  near zero after a spike at around 7Z

- for the first time since setting up the feed test from emo.unidata.ucar.edu
  to seistan and then back out to zero.unidata.ucar.edu, all HDS data was
  relayed from seistan to zero.unidata.ucar.edu

- latencies for all feeds from seistan to tornado.geos.ulm.edu
  (e.g., FSL2, IDS|DDPLUS, UNIWISC, and NNEXRAD) dropped significantly

Given these three observations from the real time statistics page:

http://www.unidata.ucar.edu/staff/chiz/rtstats/siteindex.shtml

for seistan.srcc.lsu.edu, zero.unidata.ucar.edu, and tornado.geos.ulm.edu
I conclude that something changed in the network path out of LSU or
in LANET.

Did you receive a change notification from the LSU telecomm folks?  If
not, will you contact them to find out exactly what was done?  A complete
picture of what went wrong and its fix will help others if they run into
similar problems.

Tom