A. Fill in the blanks1.Scientists and engineers devised ways to build networks that connected multiple computersacross large geographic distances, which is called Wide Area Networks(W ANs) or long-haul networks.2.ARPANET is the Internet's origins.3.Web pages are written in a computer language, which is hypertext markuplanguage(HTML)4.HTTP uses what numeric value, in decimal, of the destination port field of the TCP header?805.POP3 protocol we use to receive Email 。

6.An firewall can be used to protect a private network from outside attack.7.Today there are encryption systems that use two keys, one for encryption and one fordecryption. The key used for decryption is called a public key because it must be kept secret.The key used for encryption is called a private key because it can be distributed to anyone.8.The standard protocol for remote login is known as telnet .9.The HTML tag <br> instructs a browser to begin a new line.10.By 1982, a prototype Internet was in place and the ip technology had been tested.11.Every computer attached to the Internet must be assigned a unique numerical address calledits tcp/ip12.DSL is one of the main technologies used to provide high-speed datacommunication services over a local loop13.HTTP uses what numeric value, in decimal, of the destination port field of the TCP header?8014.STMP protocol we use to send email 。

15.The concept of embedding selectable items in text is called hypertext .B. Explain AbbreviationsPOP3:Post Office Protocol 3 URL: Uniform / Universal Resource Locator WANs:Wide Area Networks LANs:local area networks C/S:Client/Server B/S: Browser/Server ISP:Internet Service Provider P2P:Peer-to-Peer BBS:Bulletin Board System VPN:Virtual Private Network TCP:Transmission Control Protocol UDP:User Datagram Protocol HTTP:hypertext transport protocol FTP:File Transfer Protocol WWW:World Wide Web SMTP:Simple Mail Transfer Protocol DNS:Domain Name System HTML:Hypertext Markup Language IP:Internet Protocol ADSL:Asymmetric Digital Subscriber LineC. Short answer1.Assumed that your email address is jack@ and one of your friends’ ismary@.STEP1: Jack writes and edits his email.STEP2: Clients send the email to the local NUIST Mail Server through SMTP.STEP3: Mail servers use SMTP protocol to transport the mails between Mails Host on the Internet .STEP4: Jack’s mail arrives at the destination Mail server, and will be stored in the mail box of the receiver.STEP 5: Mary will receive her email through POP3 protocol.2.Please write the correct router table of R1 in the below figure. (Note: The packetcan arrive any subnet by router)3.Please give the means of every line in the below figure.Get : Request to read a Web pageHost : The server’s DNS nameUser-agent : Information about the browser and its platformServer : Information about the serverContent-type : The page’s MIME typeContent-length : The page’s length in bytes4.If two computers share an IP address, how do we know which computer is thedestination of a given datagram?Solution: Instead of connecting a computer directly to a DSL or cable modem, insert an additional device that is designed to connect multiple computers without requiring any additional IP addresses.5.What’s OSI reference model？What’s TCP/IP reference model? Please usefigure to explain your answer.6.Since all outgoing datagrams have the same return address, how can a NAT boxknow which computer should receive a response datagram that arrives from the Internet?Answer: A NAT box keeps a record of what each computer is doing.When a datagram arrives from the Internet, the NAT box consults its records to determine which computer should receive the datagram.The NAT box replaces the ‘‘to’’address of an incoming datagram with the local address of the correct destination computer.7.Please explain these header keywords ( Received, Date, From, To, Subject ) in theFrom: The sender of the messageTo: The recipient of the messageDate: The time the message was sentSubject: The subject of the messageReceived: Line added by each transfer agent along the route8.What is URL？(Please explain simply.)An identifier used to specify a particular page of web information is called a Uniform Resource Locator (URL).URL consists of 3 parts:the protocol (http), the DNS name of the host (), Port (80) and the file name (index.html)D. Web programming1. Please write the HTML in the below figure.<HTML><HEAD><TITLE>NUIST</TITLE></HEAD><BODY><TABLE BORDER =1><TR><TD>NO</TD><TD>name</TD><TD>class</TD><TD>module</TD><TD>score</TD></TR><TR><TD>20020101</TD><TD>tom</TD><TD>one</TD><TD>computer networks</TD><TD>90</TD></TR><TR><TD>20020102</TD><TD>jack</TD><TD>two</TD><TD>computer networks</TD><TD>85</TD></TR><TR><TD>20020103</TD><TD>joe</TD><TD>three</TD><TD>computer networks</TD><TD>80</TD></TR><TR>2. Please write the HTML in the below figure. Picture name: computer.JPG;Link: /jsj Text: nuist;Link: <HTML><HEAD><TITLE>Inet</TITLE></HEAD><BODY><A HREF="/jsj"><IMG SRC="computer.jpg"></A><BR><OL><LI> cars<LI> trucks<LI> buses</OL><BR><A HREF="">nuist</A></BODY></HTML>。