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

[ZhangLikun]

Hi Liang Rong

 

the resolver should do with the first way you mentioned.

 

Resolver should keep the query clients in one list,  then send the related
queres to authoritative servers if the answer can't be found in local
caches,

 

and a fail(Server Fail) answer should send back to the query clients if the
resolver still can't get the final answer after a fixed time(the default
time of bind9 is 30s)

 

 

Likun zhang

 

 

发件人: bind10-dev-bounces+zlkzhy=gmail.com at lists.isc.org
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发送时间: 2014年3月31日 17:41
收件人: bind10-dev at lists.isc.org
主题: [bind10-dev] What's the mechanism for recursive query

 

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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