At 15:10 +0800 10/31/06, Blue wrote:
Hi, all:
Currently a dual-stack device could get both IPv4 and IPv6 DNS server
list from either manually configuration or DHCPv4/v6. Is there any
regulation about the querying sequence when a DNS client wants to invoke
a query? I have dug into the RFC database and could not find any
documents concerning about the question. Or it's just an implementation
issue?
It's mostly an implementation issue. There are some conventions
though - like not flooding servers with queries while waiting.
As far as whether to prefer IPv6 or IPv4, that's a "personal"
decision. One popular belief is try IPv6 first because that's the
new thing in town, but there can be some bad experiences doing that.
For instance, you may have IPv6 locally and at the server, but the
IPv6 routing is not complete between the two.
As far as the protocol and system are concerned, it is customary to
have a time out of a few seconds to allow a server to respond to a
first query before assuming the query has gotten lost. You want to
avoid having a server get a query twice if the first response
eventually does get back to the client because the second query and
it's handling is pure bad overhead.
A good strategy for query management can improve performance. There
might be a tradeoff of what is an improvement - sometimes what is
good for a client is not good for the servers. It's not always clear
what is the best thing for all involved.
I have seen bad clients cause problems for the network. Even though
a deficient design can cause problems, trying to reach a consensus of
what is the right thing to do is not easy. This is why there is no
regulation, no standard.
You might look at RFC 1034, section 6.3.1 for a sort-of standard
mention of how a client (resolver) should behave.
--
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Edward Lewis +1-571-434-5468
NeuStar
Secrets of Success #107: Why arrive at 7am for the good parking space?
Come in at 11am while the early birds drive out to lunch.
.
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