Subject: app-layer acks in DNS

From: "Eric A. Hall" <[email-masked]>
Date: Thu, 04 Apr 2002 20:12:57 -0600

As we all know, DNS doesn't provide any kind of application-layer
flow-control or acknwoledgements. Queries either succeed or they fail, and
the outcome is only reported when processing either succeeds or fails.
However, there will often be multiple intermediate events between the
final success or failure.

Q: Would notifications about these transitional events be a bad thing?

More specifically, consider the following example. A stub resolver issues
a query to its local caching server, and as far as the stub is concerned,
the query has gone into a black-hole. Meanwhile, the cache is generating
bunches of queries, following referrals, chasing down CNAMEs, and so on.
While all of this is happening, the stub is twiddling its thumbs,
completely oblivious to everything. Given enough time, the stub will just
assume failure and then go ask another server, and that server has to go
beat up the network all over again.

Clearly there would be some benefit to having the cache tell the stub "got
some of your data, I'm on the case, hold for N seconds". The question is
whether or not the amount of extra processing and messaging load would be
a bad thing.

Thoughts?

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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