TCPIP協(xié)議原理教學課件：Chapter 12 CS、DHCP、DNS

1、2022/7/15TCP/IP Protocol Suite1Chapter 12 C/S, DHCP and DNSClient-Server modelBOOTP and DHCPDomain Name System ( DNS )2022/7/15TCP/IP Protocol Suite2Client-Server Model2022/7/15TCP/IP Protocol Suite3Client-Server ModelClient（客戶）A program running on the local machine requesting service from a serverF

2、inite：由用戶或另一應用程序啟動，服務完成時終止Active open and active closeServer（服務器）A program running on the remote machine providing service to the clientsInfinite：啟動后一直運行，除非出了問題Passive open2022/7/15TCP/IP Protocol Suite4CS關系Client與Server的關系是：多對一2022/7/15TCP/IP Protocol Suite5Concurrency（并發(fā)）ClientIteratively（循環(huán)）: run

3、ning one by oneConcurrently （并發(fā)） : running at the same timeServerConnectionless iterative server（無連接循環(huán)服務器）: use UDPConnection-oriented concurrent server（面向連接并發(fā)服務器）: use TCP2022/7/15TCP/IP Protocol Suite6Connectionless Iterative Server2022/7/15TCP/IP Protocol Suite7Connection-Oriented Concurrent Serv

4、er2022/7/15TCP/IP Protocol Suite8BOOTP and DHCP連接在Internet上的主機必須知道以下信息：Its IP address and subnet maskThe IP address of a routerThe IP address of a name serverBOOTP ( BOOTstrap Protocol，引導程序協(xié)議)RFC 951，RFC 1395、1497、1532、1542功能：為引導“無盤計算機或第一次啟動的計算機”提供以上信息C/S protocolClient：UDP 68Server：UDP 672022/7/15T

5、CP/IP Protocol Suite9BOOTP Operation2022/7/15TCP/IP Protocol Suite10BOOTP packet format2022/7/15TCP/IP Protocol Suite11DHCPDynamic Host Configuration Protocol動態(tài)主機配置協(xié)議RFC 2131FeaturesEnhances BOOTPBackward compatible with BOOTPProvides temporary IP addresses for a limited period of timeTwo databasesS

6、tatically binds physical addresses with IP addressesA pool of available IP addresses租用（Leasing）：DHCP服務器從可用IP地址池中為DHCP客戶分配一個臨時的IP，并指定這個地址可以被租用的特定時間靜態(tài)配置協(xié)議：BOOTP Server 上預先設置了BOOTP Client 的物理地址與IP地址的綁定2022/7/15TCP/IP Protocol Suite12DHCP Transition Diagram: Client2022/7/15TCP/IP Protocol Suite13DHCP Op

7、eration2022/7/15TCP/IP Protocol Suite14DHCP Operation ( cont. )2022/7/15TCP/IP Protocol Suite15Domain Name System ( DNS )Domain Name System，域名系統(tǒng)RFC 1034：Concepts and facilitiesRFC 1035：Implementation and specificationDNS功能：將Internet上主機的名字映射成為IP地址；將主機IP地址映射成為名字2022/7/15TCP/IP Protocol Suite16Name Spa

8、ce（名字空間）IP地址唯一，所以IP地址映射的名字也是唯一的名字的分配需要仔細管理兩種名字空間的組織、管理方案：Flat name space在Internet中難以實現(xiàn)A sequence of characters without structure需要集中控制（Internet范圍內(nèi)）避免二義性和重復Example: computer name in Microsoft WindowsHierarchical name space（層次名字空間）一個名字：由幾部分組成例如：名字（機構性質(zhì)，機構名字，機構部門，)例：.名字空間的管理可以實現(xiàn)分散管理2022/7/15TCP/IP Prot

9、ocol Suite17Domain Name Space（域名空間）域名空間：層次名字空間An inverted-tree structure with the root at the topLabel（標號）: a string with a max of 63 charactersLabel（標號）: a string with a max of 63 characters要求：具有同一個父節(jié)點的子節(jié)點具有不同的標號保證域名的唯一性2022/7/15TCP/IP Protocol Suite18Domain NameA sequence of labels（標號） separated b

10、y dots ( . )cn.域名.域名.域名.域名cn標號edu標號uestc標號www標號根（標號為空）2022/7/15TCP/IP Protocol Suite19Domain（域）A subtree（子樹） of the domain name space2022/7/15TCP/IP Protocol Suite20Distribution of the Domain Name Space域名空間的信息需要被存儲起來信息被分布到DNS服務器DNS serverCan be responsible ( authoritative ) for either a large or sma

11、ll domainHierarchy of DNS servers2022/7/15TCP/IP Protocol Suite21域名信息分布式存儲在多個域名服務器上一個域名服務器所負責或授權的范圍區(qū)域名服務器數(shù)據(jù)庫（區(qū)文件）中存放著這個域內(nèi)節(jié)點的信息服務器可以把其所在的域劃分成若干子域子域節(jié)點的信息：存儲在該子域（區(qū)）的域名服務器中原來的服務器保存到這些子域域名服務器的引用區(qū)（Zone）2022/7/15TCP/IP Protocol Suite22DNS ServerRoot serverA server whose zone consists of the whole treeUsual

12、ly not store any information about domainsDelegates its authority to other serversKeep references（引用） to those serversPrimary server（主服務器）Stores a file about the zone for which it is an authorityResponsible for creating, maintaining, and updating the zone fileSecondary server（次服務器）Transfers the comp

13、lete information about a zone from another server ( primary or secondary )Neither creates nor updates the zone files2022/7/15TCP/IP Protocol Suite23DNS in the InternetDNS used in the Internet域名空間劃分成三部分：InverseDomain（反向域）RootGenericDomains（類屬域）CountryDomains（國家域）2022/7/15TCP/IP Protocol Suite24DNS Re

14、solution（解析）Name-address resolutiona name an addressan address a name: inverse queryC/S applicationDNS client: resolver（解析程序）DNS serverMethodRecursive（遞歸） resolution解析程序要求服務器提供最終的域名解析Iterative （迭代） resolution解析程序不斷地向不同的服務器請求解析直至得到結(jié)果Caching2022/7/15TCP/IP Protocol Suite25Recursive Resolution2022/7/15

15、TCP/IP Protocol Suite26Iterative Resolution2022/7/15TCP/IP Protocol Suite27DNS MessagesType: request and responseFormat2022/7/15TCP/IP Protocol Suite28EncapsulationTCP port 53The resolver has prior knowledge that the size of the response message is more than 512 bytesExample: a secondary name server ( acting as a client ) needs a zone transfer from a primary serverUDP port 53The reso