[Softwires] DS-Lite & DNS

Thu, 05 Jul 2012 04:53:01 -0700


Hi all,

I'm reading in RFC 6333:

 
5.5.  DNS

   A B4 element is only configured from the service provider with IPv6.
   As such, it can only learn the address of a DNS recursive server
   through DHCPv6 (or other similar method over IPv6).  As DHCPv6 only
   defines an option to get the IPv6 address of such a DNS recursive
   server, the B4 element cannot easily discover the IPv4 address of
   such a recursive DNS server, and as such will have to perform all DNS
   resolution over IPv6.

   The B4 element can pass this IPv6 address to downstream IPv6 nodes,
   but not to downstream IPv4 nodes.  As such, the B4 element SHOULD
   implement a DNS proxy, following the recommendations of [RFC5625].


6.4.  DNS

   As noted previously, a DS-Lite node implementing a B4 element will
   perform DNS resolution over IPv6.  As a result, DNS packets are not
   expected to go through the AFTR element.

What would be the expected behavior if i configure manually an IPv4 DNS server to a host attached to the CPE?
According to RFC5625:
 
Except when required to enforce an active security or network policy
   (such as maintaining a pre-authentication "walled garden"), end-users
   SHOULD be able to send their DNS queries to specified upstream
   resolvers, thereby bypassing the proxy altogether.  In this case, the
   gateway SHOULD NOT modify the DNS request or response packets in any
   way.

Does this mean that the 6.4 statement "DNS packets are not expected to go through the AFTR element." is not always valid?

Also, can draft-ietf-dhc-dhcpv4-over-ipv6 be considered an alternative option for passing IPv4 info to clients over IPv6 in DS-Lite networks?


 
--
Tassos


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