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This draft is a work item of the Internet Architecture Board Working Group of the IETF.
Title : Architectural Concerns on the synthesis of non-existent names in DNS.
Author(s) : O. Kolkman
Filename : draft-iab-dns-synthesis-concerns-00.txt
Pages : 19
Date : 2007-4-16
There are many architectural assumptions regarding DNS behavior that
are not specified in the IETF standards documents describing DNS, but
which are deeply embedded in the behavior as expected by Internet
protocols and applications. These assumptions are inherent parts of
the network architecture of which the DNS is one component.
It has long been known that it is possible to use DNS wildcards in
ways that violate these assumptions. More recently there have been
deployments of middleboxes -- in most cases recursive nameservers or
DNS proxies at the ISP level -- that synthesize answers in ways that
not only violate these assumptions but also violate the DNS
architecture.
Experience with DNS synthesis in the DNS infrastructure have show
that the cost of violating these assumptions is significant. In this
document we provide an explanation of how DNS wildcards function, and
many examples of how their injudicious use negatively impacts both
individual Internet applications and indeed the Internet architecture
itself. We also explain that similar problems arise with the
synthesis of DNS responses by middleboxes.
We recommend that DNS wildcards should not be used in a zone unless
the zone operator has a clear understanding of the risks, and that
they should not be used without the informed consent of those
entities which have been delegated below the zone.
In addition we recommend that middleboxes do not perform DNS query
synthesis unless (1)there are informed consents of those that use the
forwarding name server, and (2)there exists an opt-out mechanism that
allows them to receive the original DNS answers.
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