[bind10-dev] What's the mechanism for recursive query

[荣亮]

Hi BIND hackers,

I'm using BIND to provision the DNS service. Now, I have a concern about
the mechanism of recursive query when a DNS server can not resolve the
client query locally. My question is described below.

The client sends query to the preferred DNS sever (which is using BIND for
DNS service), and unfortunately the preferred DNS server can't resolve the
query locally. I can imagine following two methods for how to do recursive
queries to root/authoritative DNS servers.
1) The preferred DNS server queued the client query packets and send
recursive queries to root/authoritative DNS servers immediately. After an
authoritative response obtained, the preferred DNS server returns response
the right client in the queue.
2) The preferred DNS server silently discards the client query packet but
immediately sends recursive queries to root/authoritative DNS servers. The
client may send queries to the preferred DNS server periodically in certain
interval before it is resolved. There will be a time window for the
preferred DNS server do recursive queries and receive responses from
root/authoritative DNS servers. The preferred DNS server doesn't need to
store client query information and only replies to the client when a
resource record is found in the local cache. The client query is resolved
after the second query.

Who can tell me which is the right method for recursive query when the
preferred DNS server can't resolve query locally? Or if there is another
method? Thanks in advance.

-- 

Liang Rong
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