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<HTML><HEAD>  <TITLE>BBS水木清华站∶精华区</TITLE></HEAD><BODY><CENTER><H1>BBS水木清华站∶精华区</H1></CENTER>发信人:&nbsp;<A HREF="mailto:chen@cc.nctu.edu.tw">chen@cc.nctu.edu.tw</A>&nbsp;(C.S.Chen),&nbsp;看板:&nbsp;UNIX&nbsp;<BR>标&nbsp;&nbsp;题:&nbsp;[DNS/bind]&nbsp;Lame&nbsp;Server&nbsp;?&nbsp;(理论篇&nbsp;)&nbsp;<BR>发信站:&nbsp;National&nbsp;Chiao-Tung&nbsp;University,&nbsp;Taiwan&nbsp;(Sun&nbsp;Mar&nbsp;30&nbsp;20:12:53&nbsp;1997)&nbsp;<BR>转信站:&nbsp;sobee!netnews.ntu!news.mcu!news.cs.nthu!news.cis.nctu!news-peer.nctu!n&nbsp;<BR>&nbsp;<BR>&nbsp;<BR>DNS/bind-4.9.x&nbsp;Lame&nbsp;Server&nbsp;讯息所代表的意义&nbsp;(&nbsp;理论篇&nbsp;)&nbsp;<BR>===========================================&nbsp;<BR>&nbsp;<BR>What&nbsp;is&nbsp;lame&nbsp;server&nbsp;(DNS)&nbsp;?&nbsp;<BR>&nbsp;<BR>有许多管理&nbsp;DNS&nbsp;系统的管理者,&nbsp;常会遇到,&nbsp;或看到这类的名词.&nbsp;<BR>究竟,&nbsp;&nbsp;<BR>&nbsp;&nbsp;1)&nbsp;什麽是&nbsp;Lame&nbsp;Server&nbsp;?&nbsp;(&nbsp;&quot;跛脚的&quot;&nbsp;server&nbsp;!)&nbsp;<BR>&nbsp;&nbsp;2)&nbsp;为什麽会产生&nbsp;Lame&nbsp;server&nbsp;?&nbsp;<BR>&nbsp;&nbsp;3)&nbsp;Lame&nbsp;Server&nbsp;有什麽不良影响&nbsp;?&nbsp;<BR>&nbsp;<BR>Lame&nbsp;server,&nbsp;主要的不良影响,&nbsp;就是造成不必要的&nbsp;DNS&nbsp;traffic,&nbsp;浪费&nbsp;client&nbsp;<BR>program&nbsp;和居中的&nbsp;DNS&nbsp;servers&nbsp;的&nbsp;CPU&nbsp;cycles,&nbsp;浪费使用者的时间...&nbsp;<BR>&nbsp;<BR>简单地说,&nbsp;会形成&nbsp;Lame&nbsp;server&nbsp;的条件是,&nbsp;<BR>&nbsp;&nbsp;&nbsp;a)&nbsp;NS&nbsp;delegation&nbsp;(&nbsp;被授权&nbsp;)&nbsp;<BR>&nbsp;&nbsp;&nbsp;b)&nbsp;not&nbsp;authoritative.&nbsp;(&nbsp;没有该&nbsp;domain&nbsp;zone&nbsp;全部的资料&nbsp;)&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;也就是,&nbsp;&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a)&nbsp;该&nbsp;host&nbsp;没有跑&nbsp;named&nbsp;程式&nbsp;(or&nbsp;equivalent&nbsp;DNS&nbsp;server)&nbsp;<BR>	b)&nbsp;该&nbsp;host&nbsp;有跑&nbsp;DNS&nbsp;server&nbsp;程式,&nbsp;但是起始设定档&nbsp;<BR>&nbsp;&nbsp;	&nbsp;&nbsp;&nbsp;/etc/named.boot&nbsp;(or&nbsp;equivalent)&nbsp;<BR>	&nbsp;&nbsp;&nbsp;没有对应的&nbsp;primary&nbsp;or&nbsp;secondary&nbsp;设定行.&nbsp;<BR>&nbsp;<BR>====================================================================&nbsp;<BR>所谓的&nbsp;lame&nbsp;server,&nbsp;就是,&nbsp;理论上,&nbsp;一个&nbsp;domain&nbsp;zone,&nbsp;由某个&nbsp;DNS&nbsp;host&nbsp;<BR>参与负责(可能还有其它的负责&nbsp;host),&nbsp;但是如果你问它一个理论上,&nbsp;属於该&nbsp;<BR>domain&nbsp;zone&nbsp;的问题,&nbsp;这个&nbsp;host&nbsp;却回答不出.&nbsp;&nbsp;<BR>&nbsp;==&gt;&nbsp;此时,&nbsp;这个&nbsp;host&nbsp;就形成&nbsp;lame&nbsp;server.&nbsp;<BR>&nbsp;<BR>因此,&nbsp;如果是一个&nbsp;authoritative&nbsp;server,&nbsp;底下两类情况,&nbsp;都要能回答:&nbsp;<BR>&nbsp;(以&nbsp;NCTU.edu.tw&nbsp;这个&nbsp;domain&nbsp;zone&nbsp;为例&nbsp;)&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;a)&nbsp;postive&nbsp;example:&nbsp;(事实存在,&nbsp;authoritative&nbsp;answer&nbsp;)&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-&nbsp;netnews.NCTU.edu.tw&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;cf.&nbsp;non-authoritative,&nbsp;caching&nbsp;answer&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;通常这一部份,&nbsp;很容易让人混淆.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-&nbsp;authoritative&nbsp;answer&nbsp;的&nbsp;TTL&nbsp;值,&nbsp;不会变.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-&nbsp;caching&nbsp;answer&nbsp;的&nbsp;TTL&nbsp;值,&nbsp;会递减,&nbsp;一直到零.&nbsp;(&nbsp;zero)&nbsp;如再被问到,&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;会再到&nbsp;authoritative&nbsp;DNS&nbsp;host&nbsp;去问一次,&nbsp;整个&nbsp;caching&nbsp;cycle&nbsp;再&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;重来...&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;b)&nbsp;negative&nbsp;example&nbsp;(不存在的&nbsp;domain&nbsp;zone)&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;-&nbsp;tst.NCTU.edu.tw&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;只有&nbsp;authoritative&nbsp;server&nbsp;才有全部的&nbsp;domain&nbsp;zone&nbsp;的&nbsp;data,&nbsp;因此才能&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;判定一个错误,&nbsp;不存在的&nbsp;domain&nbsp;name.&nbsp;(&nbsp;semantic&nbsp;error&nbsp;)&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;而&nbsp;caching&nbsp;server&nbsp;通常只有,&nbsp;某个&nbsp;domain&nbsp;zone&nbsp;的部份&nbsp;data,&nbsp;对於&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;某个看来,&nbsp;语法正确的的&nbsp;data,&nbsp;但却不在&nbsp;caching&nbsp;中的资料,&nbsp;只能假定&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;它是对的,&nbsp;只是刚好不在,&nbsp;必须再到该&nbsp;authoritative&nbsp;DNS&nbsp;host&nbsp;去问.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--&nbsp;因此,&nbsp;通常无法判定,&nbsp;除非对该&nbsp;entry,&nbsp;刚好有&nbsp;negative&nbsp;caching.&nbsp;<BR>&nbsp;<BR>====================================================================&nbsp;<BR>&nbsp;<BR>如果,&nbsp;真得要更清楚了解,&nbsp;为什麽会形成&nbsp;Lame&nbsp;server&nbsp;意义.&nbsp;首先,&nbsp;必须从&nbsp;DNS&nbsp;<BR>系统的授权运作了解起.&nbsp;<BR>&nbsp;<BR>DNS&nbsp;是一个分散式的阶层式管理系统,&nbsp;这个系统运作,&nbsp;奠基在两个重要观念.&nbsp;<BR>&nbsp;&nbsp;a)&nbsp;domain&nbsp;zone&nbsp;的授权.&nbsp;(&nbsp;NS&nbsp;delegation&nbsp;)&nbsp;<BR>&nbsp;&nbsp;b)&nbsp;domain&nbsp;zone&nbsp;的负责单位&nbsp;DNS&nbsp;servers,&nbsp;准备原始资料&nbsp;(&nbsp;authoritative&nbsp;data&nbsp;)&nbsp;<BR>&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;举例而言,&nbsp;<BR>&nbsp;<BR>&nbsp;--&nbsp;最顶层的&nbsp;root&nbsp;domain&nbsp;name&nbsp;server&nbsp;(&nbsp;a.root-servers.net&nbsp;等十来个),&nbsp;将&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;tw&nbsp;domain&nbsp;zone&nbsp;授权给&nbsp;moevax.edu.tw&nbsp;等&nbsp;6&nbsp;个&nbsp;DNS&nbsp;server&nbsp;管理.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;==&gt;&nbsp;因此,&nbsp;Internet&nbsp;上其它的&nbsp;DNS&nbsp;servers&nbsp;要找做&nbsp;domain&nbsp;name&nbsp;中最右边,&nbsp;<BR>	是&nbsp;tw&nbsp;者,&nbsp;必先&nbsp;contact&nbsp;这六者之一.&nbsp;<BR>&nbsp;<BR>&nbsp;--&nbsp;tw&nbsp;domain&nbsp;zone&nbsp;的管理者,&nbsp;将&nbsp;com.tw&nbsp;授权交由&nbsp;{aladdin.iii.org.tw}&nbsp;和&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;{moevax.edu.tw}&nbsp;两者管理.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;==&gt;&nbsp;因此,&nbsp;Internet&nbsp;上其它的&nbsp;DNS&nbsp;servers&nbsp;要找做&nbsp;domain&nbsp;name&nbsp;中最右边,&nbsp;<BR>	是&nbsp;com.tw&nbsp;者,&nbsp;上列的六个&nbsp;{tw}&nbsp;DNS&nbsp;servers&nbsp;会告诉它们去问这两个&nbsp;<BR>	其中之一.&nbsp;<BR>&nbsp;<BR>.....&nbsp;<BR>&nbsp;<BR>===============================================================&nbsp;<BR>至於&nbsp;DNS&nbsp;系统上&nbsp;domain&nbsp;zone&nbsp;的授权&nbsp;(&nbsp;NS&nbsp;delegation),&nbsp;更有两处.&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;1)&nbsp;parent&nbsp;zone&nbsp;授权给&nbsp;child&nbsp;zone&nbsp;的&nbsp;DNS&nbsp;servers.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--e.g.&nbsp;EDU.tw&nbsp;的&nbsp;NS&nbsp;(moevax.edu.tw)&nbsp;将&nbsp;&nbsp;NCTU.EDU.tw&nbsp;授权给&nbsp;<BR>	&nbsp;&nbsp;{ns.NCTU.edu.tw,ns2.NCTU.edu.tw,NCTU.edu.tw}&nbsp;三个&nbsp;DNS&nbsp;host&nbsp;负责.&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--&nbsp;这□所谓的授权,&nbsp;就是管理权,&nbsp;由此转出去,&nbsp;不再干预.&nbsp;<BR>	例如,&nbsp;目前如果在&nbsp;moevax.edu.tw&nbsp;定义&nbsp;tst.NCTU.edu.tw&nbsp;是无效的,&nbsp;<BR>	(除非将&nbsp;NCTU.edu.tw&nbsp;的三组&nbsp;NS&nbsp;records&nbsp;取消)&nbsp;<BR>&nbsp;<BR>	因为&nbsp;domain&nbsp;zone&nbsp;&quot;NCTU.edu.tw&nbsp;&quot;&nbsp;的管理权已经,&nbsp;授权给&nbsp;ns.NCTU.edu.tw&nbsp;<BR>	等三个&nbsp;DNS&nbsp;hosts.&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;2)&nbsp;某个&nbsp;domain&nbsp;zone&nbsp;的&nbsp;primary&nbsp;DNS&nbsp;host,&nbsp;将该&nbsp;domain&nbsp;zone&nbsp;授权给&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;其它&nbsp;secondary&nbsp;host.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--&nbsp;a)&nbsp;EDU.tw&nbsp;:&nbsp;<BR>	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;primary&nbsp;-&nbsp;moevax.edu.tw&nbsp;<BR>	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;secondary&nbsp;-&nbsp;moesun.edu.tw&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--&nbsp;b)&nbsp;NCTU.EDU.tw:&nbsp;<BR>	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;primary&nbsp;-&nbsp;ns.NCTU.edu.tw&nbsp;<BR>	&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;secondary&nbsp;-&nbsp;ns2.NCTU.edu.tw,&nbsp;NCTU.edu.tw&nbsp;<BR>&nbsp;<BR>=====================================================================&nbsp;<BR>就功能上而言,&nbsp;某个&nbsp;domain&nbsp;zone&nbsp;的&nbsp;primary/secondary,&nbsp;从其它站的&nbsp;DNS&nbsp;&nbsp;<BR>server/client&nbsp;来看,&nbsp;完全一样.&nbsp;都是该&nbsp;domain&nbsp;zone&nbsp;的&nbsp;authoritative&nbsp;server.&nbsp;<BR>&nbsp;<BR>那麽一个&nbsp;domain&nbsp;zone&nbsp;的&nbsp;primary/secondary&nbsp;究竟有何不同&nbsp;?&nbsp;可以分辨的出&nbsp;?&nbsp;<BR>&nbsp;&nbsp;a)&nbsp;一个&nbsp;domain&nbsp;zone&nbsp;一定有一个唯一的&nbsp;primary&nbsp;host.&nbsp;(one&nbsp;and&nbsp;only&nbsp;one)&nbsp;<BR>&nbsp;&nbsp;b)&nbsp;一个&nbsp;domain&nbsp;zone&nbsp;得有一个以上的&nbsp;secondary&nbsp;host&nbsp;(maybe&nbsp;none)&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;根据&nbsp;Internet&nbsp;惯例,&nbsp;一个&nbsp;domain&nbsp;zone&nbsp;应该有一个以上的&nbsp;secondary&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DNS&nbsp;host.&nbsp;国内,&nbsp;过去在这一方面,&nbsp;似乎没有要求.&nbsp;因此,&nbsp;许多单位&nbsp;<BR>	一个&nbsp;secondary&nbsp;host&nbsp;都没有.&nbsp;这样子,&nbsp;reliability&nbsp;and&nbsp;performance&nbsp;<BR>	实在堪虑.&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;c)&nbsp;一个&nbsp;domain&nbsp;zone&nbsp;的&nbsp;primary&nbsp;host&nbsp;负责准备原始资料.&nbsp;而&nbsp;secondary&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;则从&nbsp;primary,&nbsp;将该&nbsp;domain&nbsp;zone&nbsp;的资料,&nbsp;全部&nbsp;mirror&nbsp;过来.&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Note:&nbsp;关於&nbsp;primary/secondary&nbsp;host&nbsp;的说明&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;========================================================&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;server&nbsp;A&nbsp;-&nbsp;primary&nbsp;host&nbsp;for&nbsp;domain&nbsp;zone-1,&nbsp;domain&nbsp;zone-2&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;secondary&nbsp;host&nbsp;for&nbsp;domain&nbsp;zone-3&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;server&nbsp;B&nbsp;-&nbsp;secondary&nbsp;host&nbsp;for&nbsp;domain&nbsp;zone-1&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;		primary&nbsp;host&nbsp;for&nbsp;domain-3&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;server&nbsp;C&nbsp;-&nbsp;secondary&nbsp;host&nbsp;for&nbsp;domain&nbsp;zone-2,&nbsp;zone-3&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1)&nbsp;A&nbsp;到&nbsp;B&nbsp;取&nbsp;domain&nbsp;zone-3&nbsp;的资料,&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2)&nbsp;B&nbsp;到&nbsp;A&nbsp;取&nbsp;domain&nbsp;zone-1&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3)&nbsp;C&nbsp;到&nbsp;A&nbsp;取&nbsp;domain&nbsp;zone-2&nbsp;的资料,&nbsp;C&nbsp;到&nbsp;B&nbsp;取&nbsp;domain&nbsp;zone-3&nbsp;的资料&nbsp;<BR>&nbsp;<BR>□&nbsp;&nbsp;d)&nbsp;唯一可能分辨的,&nbsp;理论上只有&nbsp;该&nbsp;domain&nbsp;zone&nbsp;的&nbsp;SOA&nbsp;记录.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;origin&nbsp;这一栏,&nbsp;应该要填该&nbsp;domain&nbsp;zone&nbsp;的&nbsp;primary&nbsp;host.&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;--&nbsp;但是,&nbsp;如果填错了,&nbsp;就看不出来了.&nbsp;<BR>&nbsp;<BR>Script&nbsp;started&nbsp;on&nbsp;Sun&nbsp;Mar&nbsp;30&nbsp;19:17:21&nbsp;1997&nbsp;<BR>netnews%&nbsp;21:&gt;nslookup&nbsp;<BR>Default&nbsp;Server:&nbsp;&nbsp;ns.NCTU.edu.tw&nbsp;<BR>Address:&nbsp;&nbsp;140.113.250.135&nbsp;<BR>&nbsp;<BR>><I>&nbsp;set&nbsp;type=soa&nbsp;</I><BR>><I>&nbsp;nctu.edu.tw.&nbsp;</I><BR>Server:&nbsp;&nbsp;ns.NCTU.edu.tw&nbsp;<BR>Address:&nbsp;&nbsp;140.113.250.135&nbsp;<BR>&nbsp;<BR>nctu.edu.tw&nbsp;<BR>	origin&nbsp;=&nbsp;ns.nctu.edu.tw&nbsp;<BR>	mail&nbsp;addr&nbsp;=&nbsp;hostmaster.nctu.edu.tw&nbsp;<BR>	serial&nbsp;=&nbsp;1997032700&nbsp;<BR>	refresh&nbsp;=&nbsp;86400&nbsp;(1&nbsp;day)&nbsp;<BR>	retry&nbsp;&nbsp;&nbsp;=&nbsp;1800&nbsp;(30&nbsp;mins)&nbsp;<BR>	expire&nbsp;&nbsp;=&nbsp;1728000&nbsp;(20&nbsp;days)&nbsp;<BR>	minimum&nbsp;ttl&nbsp;=&nbsp;259200&nbsp;(3&nbsp;days)&nbsp;<BR>nctu.edu.tw	nameserver&nbsp;=&nbsp;ns.nctu.edu.tw&nbsp;<BR>nctu.edu.tw	nameserver&nbsp;=&nbsp;ns2.nctu.edu.tw&nbsp;<BR>nctu.edu.tw	nameserver&nbsp;=&nbsp;nctu.edu.tw&nbsp;<BR>ns.nctu.edu.tw	internet&nbsp;address&nbsp;=&nbsp;140.113.250.135&nbsp;<BR>ns2.nctu.edu.tw	internet&nbsp;address&nbsp;=&nbsp;140.113.6.2&nbsp;<BR>nctu.edu.tw	internet&nbsp;address&nbsp;=&nbsp;140.113.1.1&nbsp;<BR>><I>&nbsp;netnews%&nbsp;22:&gt;exit&nbsp;</I><BR>exit&nbsp;<BR>&nbsp;<BR>script&nbsp;done&nbsp;on&nbsp;Sun&nbsp;Mar&nbsp;30&nbsp;19:17:42&nbsp;1997&nbsp;<BR>&nbsp;<BR>--&nbsp;&nbsp;<BR>Joe.&nbsp;C.S.Chen,&nbsp;&nbsp;<A HREF="mailto:chen@cc.nctu.edu.tw">chen@cc.nctu.edu.tw</A>&nbsp;<BR>&nbsp;<BR>*******&nbsp;&nbsp;Knowledge&nbsp;is&nbsp;of&nbsp;two&nbsp;kinds.&nbsp;&nbsp;We&nbsp;know&nbsp;a&nbsp;subject&nbsp;ourselves,&nbsp;&nbsp;********&nbsp;<BR>&nbsp;	&nbsp;or&nbsp;we&nbsp;know&nbsp;where&nbsp;we&nbsp;can&nbsp;find&nbsp;information&nbsp;upon&nbsp;it.&nbsp;<BR><CENTER><H1>BBS水木清华站∶精华区</H1></CENTER></BODY></HTML>

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