TCPIP协议原理教学课件：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（客户）A program running on the local machine requesting service from a serverF

2、inite：由用户或另一应用程序启动，服务完成时终止Active open and active closeServer（服务器）A program running on the remote machine providing service to the clientsInfinite：启动后一直运行，除非出了问题Passive open2022/7/15TCP/IP Protocol Suite4CS关系Client与Server的关系是：多对一2022/7/15TCP/IP Protocol Suite5Concurrency（并发）ClientIteratively（循环）: run

3、ning one by oneConcurrently （并发） : running at the same timeServerConnectionless iterative server（无连接循环服务器）: use UDPConnection-oriented concurrent server（面向连接并发服务器）: 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连接在Internet上的主机必须知道以下信息：Its IP address and subnet maskThe IP address of a routerThe IP address of a name serverBOOTP ( BOOTstrap Protocol，引导程序协议)RFC 951，RFC 1395、1497、1532、1542功能：为引导“无盘计算机或第一次启动的计算机”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动态主机配置协议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服务器从可用IP地址池中为DHCP客户分配一个临时的IP，并指定这个地址可以被租用的特定时间静态配置协议：BOOTP Server 上预先设置了BOOTP Client 的物理地址与IP地址的绑定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，域名系统RFC 1034：Concepts and facilitiesRFC 1035：Implementation and specificationDNS功能：将Internet上主机的名字映射成为IP地址；将主机IP地址映射成为名字2022/7/15TCP/IP Protocol Suite16Name Spa

8、ce（名字空间）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细管理两种名字空间的组织、管理方案：Flat name space在Internet中难以实现A sequence of characters without structure需要集中控制（Internet范围内）避免二义性和重复Example: computer name in Microsoft WindowsHierarchical name space（层次名字空间）一个名字：由几部分组成例如：名字（机构性质，机构名字，机构部门，)例：.名字空间的管理可以实现分散管理2022/7/15TCP/IP Prot

9、ocol Suite17Domain Name Space（域名空间）域名空间：层次名字空间An inverted-tree structure with the root at the topLabel（标号）: a string with a max of 63 charactersLabel（标号）: a string with a max of 63 characters要求：具有同一个父节点的子节点具有不同的标号保证域名的唯一性2022/7/15TCP/IP Protocol Suite18Domain NameA sequence of labels（标号） separated b

10、y dots ( . )cn.域名.域名.域名.域名cn标号edu标号uestc标号www标号根（标号为空）2022/7/15TCP/IP Protocol Suite19Domain（域）A subtree（子树） of the domain name space2022/7/15TCP/IP Protocol Suite20Distribution of the Domain Name Space域名空间的信息需要被存储起来信息被分布到DNS服务器DNS serverCan be responsible ( authoritative ) for either a large or sma

11、ll domainHierarchy of DNS servers2022/7/15TCP/IP Protocol Suite21域名信息分布式存储在多个域名服务器上一个域名服务器所负责或授权的范围区域名服务器数据库（区文件）中存放着这个域内节点的信息服务器可以把其所在的域划分成若干子域子域节点的信息：存储在该子域（区）的域名服务器中原来的服务器保存到这些子域域名服务器的引用区（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（主服务器）Stores a file about the zone for which it is an authorityResponsible for creating, maintaining, and updating the zone fileSecondary server（次服务器）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域名空间划分成三部分：InverseDomain（反向域）RootGenericDomains（类属域）CountryDomains（国家域）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（递归） resolution解析程序要求服务器提供最终的域名解析Iterative （迭代） resolution解析程序不断地向不同的服务器请求解析直至得到结果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