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LOC records in ac.uk

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12th Nov 2015 | 11:26

Since September 1995 we have had a TXT record on cam.ac.uk saying "The University of Cambridge, England". Yesterday I replaced it with a LOC record. The TXT space is getting crowded with things like Google and Microsoft domain authentication tokens and SPF records.

When I rebuilt our DNS servers with automatic failover earlier this year, I used the TXT record for a very basic server health check. I wanted some other ultra-stable record for this purpose which is why I added the LOC record.

What other LOC records are there under ac.uk, I wonder?

Anyone used to be able to AXFR the ac.uk zone but that hasn't been possible for a few years now. But there is a public FOI response containing a list of ac.uk domains from 2011 which is good enough.

A bit of hackery with adns and 20 seconds later I have:

abertay.ac.uk.        LOC 56 46  4.000 N 2 57  5.000 W 50.00m   1m 10000m 10m
cam.ac.uk.            LOC 52 12 19.000 N 0  7  5.000 E 18.00m 10000m 100m 100m
carshalton.ac.uk.     LOC 51 22 17.596 N 0  9 58.698 W 33.00m  10m   100m 10m
marywardcentre.ac.uk. LOC 51 31 15.000 N 0  7 19.000 W  0.00m   1m 10000m 10m
midchesh.ac.uk.       LOC 53 14 58.200 N 2 32 15.190 E 47.00m   1m 10000m 10m
psc.ac.uk.            LOC 51  4 17.000 N 1 19 19.000 W 70.00m 200m   100m 10m
rdg.ac.uk.            LOC 51 26 25.800 N 0 56 46.700 W 87.00m   1m 10000m 10m
reading.ac.uk.        LOC 51 26 25.800 N 0 56 46.700 W 87.00m   1m 10000m 10m
ulcc.ac.uk.           LOC 51 31 16.000 N 0  7 40.000 W 93.00m   1m 10000m 10m
wessexsfc.ac.uk.      LOC 51  4 17.000 N 1 19 19.000 W 70.00m 200m   100m 10m
wilberforce.ac.uk.    LOC 53 46 28.000 N 0 16 42.000 W  0.00m   1m 10000m 10m

A LOC record records latitude, longitude, altitude, diameter, horizontal precision, and vertical precision.

The cam.ac.uk LOC record is supposed to indicate the location of the church of St Mary the Great, which has been the nominal centre of Cambridge since a system of milestones was set up in 1725. The precincts of the University are officially the area within three miles of GSM which corresponds to a diameter a bit less than 10km. The 100m vertical precision is enough to accommodate the 80m chimney at Addenbrookes.

There are a couple of anomalies in the other LOC records.

abertay.ac.uk indicates a random spot in the highlands, not the centre of Dundee as it should.

midchesh.ac.uk should be W not E.

A lot of the records use the default size of 1m diameter and precision of 10km horizontal and 10m vertical.

You can copy and paste the lat/long into Google Maps to see where they land :-)

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Comments {5}

from: anonymous
date: 12th Nov 2015 11:37 (UTC)

Hmm.
0.00 N 0.00W -6378100 6378100 0 0 would be correct but unhelpful, I think. I wonder what would break?

-- mkb

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Tony Finch

from: fanf
date: 12th Nov 2015 11:42 (UTC)

Hah :-) The LOC record is designed to accommodate that kind of thing (though the size and precision values are stored with only one significant figure). The RFC says:
   Since 20000000m (represented by the value 0x29) is greater
   than the equatorial diameter of the WGS 84 ellipsoid
   (12756274m), it is therefore suitable for use as a
   "worldwide" size.


Edited at 2015-11-12 12:17 pm (UTC)

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Ben Harris

from: bjh21
date: 12th Nov 2015 13:23 (UTC)

Completely stupid plan: Bes++ understands that servers are in racks that are in rooms that are in buildings, and knows the University Map references for buildings. The Map can give you the OpenStreepMap object ID corresponding to a Map reference, and OSM can then give you the outline of that object. Walk all these databases, and you could construct a LOC record for many UIS boxes (and vboxes). Which would be of no use to anyone.

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Ben Harris

from: bjh21
date: 12th Nov 2015 18:32 (UTC)

wraith:~/bes++/clients$ ./loc recdns-rnb.csi.cam.ac.uk
recdns-rnb.csi.cam.ac.uk. LOC 52 12 40.186803 N 0 5 37.048031 E 0m 1m 92.100135m
wraith:~/bes++/clients$ ./loc recdns-cnh.csi.cam.ac.uk
recdns-cnh.csi.cam.ac.uk. LOC 52 12 13.018143 N 0 7 13.174508 E 0m 1m 80.390155m
wraith:~/bes++/clients$ ./loc recdns-sby.csi.cam.ac.uk
recdns-sby.csi.cam.ac.uk. LOC 52 12 41.349242 N 0 5 13.782837 E 0m 1m 48.933501m
wraith:~/bes++/clients$ ./loc recdns-wcdc.csi.cam.ac.uk
wraith:~/bes++/clients$ # the location of WCDC is secret

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Tony Finch

from: fanf
date: 12th Nov 2015 23:59 (UTC)

That is very cool and also quite funny :-)

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