Greetings,
I've reviewed this draft as part of the TSV Area Review Team, paying special
attention to transport-related concerns. Please take these as any other IETF
last call comments.
Summary: This draft clearly describes online testing of possible DNSSEC
failures, and how to interpret the results. It does not appear to pose any
transport-related danger, and is broadly ready for publication as a BCP.
I do have the following questions, though:
(1) Section 3.1: "The tests are designed to check for one feature at a time".
This is generally A Good Thing, but it does seem that there should be some
attempt to economize on packets sent. This is not as much a problem when
testing recursive resolvers, since they should only need to be run when a host
introduces itself to a neighboring recursive resolver and the test traffic
shouldn't leave the site. However, section 3.2 are designed to run on the open
Internet, and seems to suggests that tests 3.2.1-3.2.3 should be run *first*,
then followed by the fourteen tests in section 3.1. In the "best case" future
for this document, that every stub resolver implements this online testing
automatically, every packet saved is significant.
Some optimizations are obvious: 3.2.1 replaces 3.1.1, 3.2.3 replaces 3.1.2. The
document should note these (even though they're trivial). Some optimizations
have already been made: 3.1.5, 3.1.10, 3.3. test multiple conditions. Are there
any other tests that could be combined (e.g. the TCP connectivity and EDNS0
tests) without losing fidelity?
(2) Could the retries advised in section 5 be abused to cause a resolver
running roadblock avoidance to send unnecessary test traffic? It seems that
injecting an error, illegal, or bogus response could induce multiple retries,
though it's not clear that the amplification factor makes this worth it.
(2) In section 6, the draft raises the possibility of unstable networking after
connection (e.g. in a captive portal situation); guidance to refrain from
flooding the network with test traffic during this instability might be useful.
Perhaps explicitly link the DNSSEC checks to a "network proves to be usable"
signal (either from the application or the operating system)?
Thanks, cheers,
Brian (as TSV-ART reviewer)
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