计算机专业英语22-IP-Addresses-&-Domain-Name-System课件.pptx

1、LessonIP Addresses&IP Addresses&Domain Name SystemDomain Name System221.What is IP address?2.Please describe two forms of IP address.Warm-up Exercises Warm-up Exercises IP AddressIP地址，网络地址Internet Protocol 网际协议decimal format 十进制格式 binary form 二元型octet 八位位组node 节点infancy 初期cumbersome 笨重的，累赘的，难处理的 Dom

2、ain Name System(DNS)域名系统Word Word PreparationPreparationEvery machine on the Internet has a unique identifying number,called an IP Address.The IP stands for Internet Protocol,which is the language that computers use to communicate over the Internet.A protocol is the pre-defined way that someone who

3、wants to use a service talks with that service.The someone could be a person,but more often it is a computer program like a Web browser.A typical IP address looks like this:216.27.61.137(read as:two-one-six-dot-two-seven-dot.Or two hundred and sixteen dot twenty seven dot.)Text协议是使用者与服务通信时要用的预定语言To

4、make it easier for us humans to remember,IP addresses are normally expressed in decimal format as a dotted decimal number like the one above.But computers communicate in binary form.Look at the same IP address in binary:11011000.00011011.00111101.10001001(read as:one-one-zero-one-one-zero-zero-zero-

5、dot.)The four numbers in an IP address are called octets,because they each have eight positions when viewed in binary form.Text为了便于记忆，IP地址通常表示成上述十进制格式，称为点号十进制数If you add all the positions together,you get 32,which is why IP addresses are considered 32-bit numbers.Since each of the eight positions ca

6、n have two different states(1 or zero),the total number of possible combinations per octet is 28(read as twos power of eight)or 256.So each octet can contain any value between zero and 255.Combine the four octets and you get 232(read as twos power of thirty two)or a possible 4,294,967,296 unique val

7、ues!Out of the almost 4.3 billion possible combinations,certain values are restricted from use as typical IP addresses.For example,the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.Text在这43亿种组合中，有些值只限于作为特定IP地址The octets serve a purpose

8、other than simply separating the numbers.They are used to create classes of IP addresses that can be assigned to a particular business,government or other entity based on size and need.The octets are split into two sections:Net and Host.The Net section always contains the first octet.It is used to i

9、dentify the network that a computer belongs to.Host(sometimes referred to as Node)identifies the actual computer on the network.The Host section always contains the last octet.There are five IP classes plus certain special addresses.TextWhen the Internet was in its infancy,it consisted of a small nu

10、mber of computers hooked together with modems and telephone lines.You could only make connections by providing the IP address of the computer you wanted to establish a link with.For example,a typical IP address might be 216.27.22.162.This was fine when there were only a few hosts out there,but it be

11、came unwieldy as more and more systems came online.Text在Internet初期，只有少量计算机通过调制解调器和电话线连接起来The first solution to the problem was a simple text file maintained by the Network Information Center that mapped names to IP addresses.Soon this text file became so large it was too cumbersome to manage.In 1983

12、,the University of Wisconsin created the Domain Name System(DNS),which maps text names to IP addresses automatically.TextIPA set of formal rules describing how to transmit data,especially across a network.Low level protocols define the electrical and physical standards to be observed,bit-and byte-or

13、dering and the transmission and error detection and correction of the bit stream.High level protocols deal with the data formatting,including the syntax of messages,the terminal to computer dialogue,character sets,sequencing of messages etc.Many protocols are defined by RFCs or by OSI.The network la

14、yer for the TCP/IP protocol suite widely used on Ethernet networks,defined in STD 5,RFC 791.IP is a connectionless,best-effort packet switching protocol.It provides packet routing,fragmentation and re-assembly through the data link layer.IPv4 is the version in widespread use and IPv6 is just beginni

15、ng to come into use in 2000.Key TermsProtocolClassEight bits.This term is used in networking,in preference to byte,because some systems use the term byte for things that are not 8 bits long.One of three types of Internet addresses distinguished by their most significant bits.HostA computer connected

16、 to a network.The term node includes devices such as routers and printers which would not normally be called hosts.Key TermsOctetQuestionsp What is IP address?p Please describe two forms of IP address.p How many classes of IP address are there?p How to map text name into IP address?ExerciseTranslate

17、 the following sentences into Chinesep Every machine on the Internet has a unique identifying number,called an IP Address.The IP stands for Internet Protocol,which is the language that computers use to communicate over the Internet.p The someone could be a person,but more often it is a computer prog

18、ram like a Web browser.p The four numbers in an IP address are called octets,because they each have eight positions when viewed in binary form.If you add all the positions together,you get 32,which is why IP addresses are considered 32-bit numbers.ExerciseSimple writingp Please describe how to map text name into IP address.Exercise THANK YOU！