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[NOAAPORT #YED-861676]: LDM and 'private' network use



Hi Brice,

re:
> We are currently using LDM to move data between workstations in our
> network and to move data between NASA and Air Force sites.  We have a
> mix of standard weather data, including WMO, Nexrad, and NOAAPort
> gridded data.  In short everything that comes across NOAAPort.

OK.  We move all of the data available on NOAAPORT using the LDM as well.

> Added to
> this stream we have various internal data related to space operations,
> including basic text files, BUFR'ized balloon data, TIF images, and csv
> files.  We are currently considering an expanded use of LDM to move
> files between networks here at Johnson Space Center.

Sounds good.

> I am trying to determine a way to reduce the network bandwidth on some
> lines between the networks and am looking at using the FEEDTYPES to
> filter which data would be sent to which systems.  What I need to know
> before I go too far down this path is whether or not LDM knows anything
> about the data 'inside' a feedtype, or is it simply a designator field
> in the data header used by LDM.

The LDM is data type agnostic: it does not know the contents of the products
it moves, nor does it need to.

> If it's 'only' a designator (and I know
> that the 'EXP' type is, because it handles many diverse types for us
> already), then we can use the existing types to block out the data that
> we are transferring.

The feed types are a convenience.  We developed the feed type concept way back
in the Family of Services days.  They can be used to organize data transmissions
but are not strictly needed.  LDM-6.4.x includes the capability to limit
the data in any feed type to downstream hosts.  The limiting is done through
a regular expression in the exact same way that is done in ldmd.conf 'request'
lines.  The set of data that gets sent to a site requesting data is the
intersection of the downstream site's request regular expression and the
set of data that the site is allowed to receive.  The implementation of
this limiting capability essentially eliminates the need for multiple
feed types.

> This wouldn't cause issues to the IDD world
> because we are not putting our data into that stream.

OK.  I was going to mention the clash that would occur if your relay machine(s)
were to also process data available in the IDD, but it is obvious that you
understand the potential conflict already :-)

> I believe that
> you folks can tell me the answer faster than I can scan through the code
> and come with it.

Yup.

Just so you know: There are a number of sites that are using the LDM for
private data distribution networks (the National Weather Services of Spain,
South Korea, etc.).  The folks running those networks use feed types to
segregate data flows in the same way that we do in the IDD.

> Thanks for the help,

No worries.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: YED-861676
Department: Support IDD
Priority: Normal
Status: Closed


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