《(精品)1-4 主服务器和辅服务器.ppt》由会员分享，可在线阅读，更多相关《(精品)1-4 主服务器和辅服务器.ppt（12页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、 2007 Infoblox Inc.All Rights Reserved.第四节第四节:主服务器和辅助服务器、计时器和区域传送主服务器和辅助服务器、计时器和区域传送什么是Masters,Primaries,and Slaves?DNS服务涉及哪些时间，这些时间从何而来?DNS缓存是如何工作的?区域传送是如何进行的?Masters&Slaves-2 2007 Infoblox Inc.All Rights Reserved.服务器回答的时候可能是权威的也可能不是服务器回答的时候可能是权威的也可能不是Header:rd=1Question:A record for ?AnswerAuthori
2、tyAdditionalDNS Resolver这是我缓存里的回答或者这是我通过询问其他服务器知道的，这不是一个权威应答Header:aa=0Answer: is 192.253.253.8AuthorityAdditionalQuestion:A record for ?这是一个权威应答，因为我是这个管理这个区的权威服务器(Note：这是BIND 9 的回答)Header:aa=1Answer: is 192.253.253.8AuthorityAdditionalQuestion:A record for ?Masters&Slaves-3 2007 Infoblox Inc.All Ri
3、ghts Reserved.无论主还是从，都是权威应答无论主还是从，都是权威应答MasterSlavea.Com的地址记录?Header:aa=1Answer: is 192.253.253.8Header:aa=1Answer: is 192.253.253.8zone data“”“”主服务器和从服务器都可以给出权威应答Masters&Slaves-4 2007 Infoblox Inc.All Rights Reserved.一个服务器可以既是主又是从一个服务器可以既是主又是从 发生在多个区的情况发生在多个区的情况主服务器通过区域传送向从服务器发送记录从服务器从主服务器上获取记录.从服务
4、器也被称为辅助服务器Master“” zone dataSlave“”Slave“”主、从、首选、备选都是内部名称，他们表明了服务器是如何获取区域信息的。对外而言，他们是没有区别的都主、从、首选、备选都是内部名称，他们表明了服务器是如何获取区域信息的。对外而言，他们是没有区别的都是权威的服务器是权威的服务器Master“”主服务器通过手动添加记录Master“” zone dataSlave“”Slave“”Masters&Slaves-5 2007 Infoblox Inc.All Rights Reserved.Refresh,Retry,ExpireSOA Resource Record
5、Slave name serverNegative caching TTLSOA Resource RecordAny caching name serverRTT(round trip time)Measured by resolving name serverResolving name serverTimerWhere it comes fromWho cares计时器影响着更新和缓存的信息计时器影响着更新和缓存的信息TimerWhere it comes fromWho caresTTL(time to live)Individual Resource RecordAny cachin
6、g name server$dig www.dns.pn.;ANSWER SECTION:www.dns.pn.86400 IN A 192.245.12.31Refresh,Retry,ExpireSOA Resource RecordSlave name serverNegative caching TTLSOA Resource RecordAny caching name serverRTT(round trip time)Measured by resolving name serverResolving name serverTimerWhere it comes fromWho
7、cares$dig dns.pn soa;ANSWER SECTION:dns.pn.86400 IN SOA NS.Opus1.COM.hostmaster.Opus1.COM.2006030200 86400 7200 2592000 10800refresh=86400(1D)retry =7200(2H)expire =2592000(4w2d)minimum ttl=10800(3H)Masters&Slaves-6 2007 Infoblox Inc.All Rights Reserved.Refresh,Retry,and Expiration Govern the Master
8、/Slave RelationshipA Slave will ask every“refresh”,retries every“retry”and flushes cache if no answer in“expire” zone dataMaster“”Slave“”cache IN SOA .(2006013100 ;Serial number 86400 ;refresh 1x per day 7200 ;retry every 2 hours 2592000 ;expire after 1 month 86400 ;negative TTL is 1 day )“DNS Class
9、ic”IN SOA .(2006013100 ;Serial number 1d ;refresh 1x per day 2h ;retry every 2 hours 30d ;expire after 1 month 1h ;negative TTL is 1 hour )Bind 8&9Send me your SOAAXFRAXFR stands for Asynchronous transferMasters&Slaves-7 2007 Infoblox Inc.All Rights Reserved.TTL Tells Other Name Servers How Long to
10、Cache DataDomainTTLClassTypeRDATA1dINA192.253.253.8Name servercacheAuthoritative for“”Responses to clients are sent with smaller and smaller TTLs.When the TTL expires,the name server will have to query the authoritative server ?TTL=?TTL=?TTL=2hrMasters&Slaves-8 2007 Infoblox Inc.All Rights Reserved.
11、cacheCaching Has Some Subtle BehaviorsAuthoritative for“dns.pn”Nameserverxyzzy.dns.pn?NXDOMAIN;aa=1(name does not exist)An authoritative negative answer is cacheddig xyzzy.dns.pn;Got answer:;-HEADER-opcode:QUERY,status:NXDOMAIN,id:25691;flags:qr aa rd;QUERY:1,ANSWER:0,AUTHORITY:1,ADDITIONAL:0$TTL 4h
12、 ;default TTL is 4 hours 2h IN SOA .Hostmaster.dns.pn.(2006021705 ;serial number 3h ;refresh every 3 hours 1h ;retry every hour 7d ;expire after 1 week 1h ;negative TTL is 1 hour )Q:How long to keep authoritative negative answers?A:The TTL for negative answers is found in the zone SOA recordMasters&
13、Slaves-9 2007 Infoblox Inc.All Rights Reserved.Name Servers Try to Be Smart When They Ask QuestionscomnorthsouthaA name server chooses the closest of the 13 roots to send its initial query to-it measures the Round Trip Time on all keeps and builds a table“default”name serverWhat is the address of ?H
14、ere is a list of the com name serversQuery:rd=1rd=0“”There actually are 13 rootsWhich root should I ask for the com name servers?Do I have RTT times?Choose fastest!Seed RTT table with low,random valuesyesnoMasters&Slaves-11 2007 Infoblox Inc.All Rights Reserved.Zone Transfers Got More Sophisticated
15、RecentlyFull zone zone dataMaster“”Slave“”“DNS Classic”Request AXFREvery“refresh,”get SOA to check serial numberNew!Improved!DNS Notify!NOTIFY:zone has been updatedFull zone fileRequest AXFRSlaves can be notified and updated immediately after a zone changeMasters&Slaves-12 2007 Infoblox Inc.All Righ
16、ts Reserved.The Slave Can Also Ask for Recent Changes OnlyFull zone zone dataMaster“”Slave“”“DNS Classic”Request AXFRCheck serial every refresh intervalNew!Improved!DNS IXFR!NOTIFY:zone has been updatedRequest IXFR since serial 2006021403Slaves can request incremental updates only;only works well if most changes made via UpdatePartial zone file