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Re: Suggested LDM updates

Bob Lipschutz wrote:

> Hi, Anne.  How's it going?
>
> Hey, in a recent discussion in our FD/NIMBUS development group
> Amenda mentioned that she had run into you and that you said
> you were beginning to think about new enhancements to LDM.
> I was forthwith nominated to pass on a couple of suggestions
> that we've had on our wishlist for quite some time... so,
> here they are:
>
> 1.  Change CDC checksum method
>
> Currently the CDC checksum, which is used in part to filter duplicate
> messages, works on only the data part of the message.  Paul Hamer suggests
> that the calculation include elements of the prod_info structure.  He
> talked with  Glenn Davis about this and it was thought at the time to be a
> good idea.
>
> This would allow us to relabel the product and insert it back into the
> product queue.  One example of this is our retransmission of UPS ACARS
> data that is filtered in NIMBUS, relabeled and distributed to NCAR.
> We presently need to different machines/queues to do this.
>
> 2.  Product-specific "allow" mechanism
>
> I know that Joan and Amenda have mentioned this one ever since v5
> eliminated this capability...
>
> We have several proprietary data sets that we distribute via LDM to
> particular users.  Unfortunately, the relatively coarse allow-by-FeedType
> in v5 makes it difficult to control the data going out.  We would much
> prefer having the option of finer control over who gets what data by
> data identifier.
>
> Thanks for asking/listening!  Please let us know if you think either of
> these suggestions might figure into your upgrades (or not!)
>
>                 Regards,
>
>                         Bob Lipschutz
>                         303-497-6636

Hi Bob!

It's nice to hear from you.   We will discuss your requests.

I have some knowledge about the checksum issue - I recently modified the code
so that if the user chose to do so, the sequence number would not be included
in the checksum.  This was so that products that were identical except for
the sequence number would indeed be considered identical by the LDM.   This
philosophy sounds like the opposite of what you want.   One other data point:
Steve Danz at AWC has a situation similar to yours and would like the same.
I'll bring it up and see what people say.

I'll also find out why the product-specific "allow" mechanism was taken out.

Anne

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Anne Wilson                     UCAR Unidata Program
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                                  Boulder, CO  80307
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