Re: [dns-wg] AAAA lookup misbehaviour

["Alvaro Vives" <]

Hi David,

Only problems with DNS servers will be covered? I mean, won't you include something related with resolvers.

I can send some info regarding a bug in the resolver library of Windows XP+SP1 and Windows 2003, which causes a failure when a domain name has A and AAAA records.

Best regards,
Alvaro Vives
Consulintel

----- Original Message ----- 
From: "David Malone" dwmalone@localhost
Cc: "Peter Koch" pk@localhost; niallm@localhost
Sent: Thursday, July 01, 2004 4:54 PM
Subject: [dns-wg] AAAA lookup misbehaviour


> At the last RIPE meeting I was given an action item:
> 
> Write up a draft RIPE document summarizing the observations made
> regarding AAAA resolution problems. Circulate to the list,
> initiate discussion what to, i.e. whom to approach with the list
> of errors/problems seen.
> 
> I checked with Peter, and he says the documents are pretty freeform,
> so I've written a few paragraphs, included below.
> 
> David
> 
> 
> 
> This document is a short description of problems with certain DNS
> systems that have come to light with the deployment of IPv6 enabled
> software.
> 
> ---
> 
> One of the services that DNS provides is a facility for mapping
> host names to IPv4 addresses. This is probably the most common used
> service that DNS provides, and is achieved requesting a record of
> type "A" for the host name. Records of type A can only store an
> IPv4 address, and so with the introduction of IPv6, a new record
> type, AAAA has been introduced. It is becoming increasingly common
> for software to first issue a request of type AAAA, and if no record
> of that type is found then to issue a request for a record of type
> A.
> 
> A request for a record of type AAAA causes no problems for most DNS
> servers, however some DNS servers have been found that have problems
> answering queries not of type A. The technical details of these
> problems are explained in the IETF draft document
> draft-ietf-dnsop-misbehavior-against-aaaa-01.txt.  In 2004, about
> 0.5--1% of name servers seem to have to have a problem of this
> nature.  The end result of these issues is that connecting to a
> site using a problematic name server may be impossible, intermittent
> or significantly delayed.
> 
> To prevent introducing more DNS servers with such issues, testing
> of new DNS equipment should include checking that the response for
> records is in accordance with the RFCs. As DNS load balancing
> software has often fallen foul of these problems, particular care
> should be taken in testing and validating such systems.
> 
> The fact that problematic nameservers exist is in itself a problem.
> Where these issues cause direct inconvenience, the maintainers of
> the server and the maintainers of the DNS data should be notified
> to allow a normal service to be restored. However, often it is
> difficult for end users to identify the source of these problems,
> (for example, where an image embedded in a web page being served
> from a host with a problem hostname).
> 
> It is also possible to automatically produce lists of names and
> nameservers that exhibit these problems. Clearly it is possible to
> automatically mail hostmaters or to publish "hall of shame" lists
> based on such data. It is unclear if such actions would achieve
> any useful effect, as service maintainers are usually primarily
> concerned about complaints directly from paying users!
> 
> 


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