1、應用層應用層表示層表示層會話層會話層傳輸層傳輸層物理層物理層數據鏈路層數據鏈路層網絡層網絡層7654321OSI/RM應用層應用層傳輸層傳輸層網絡接口層網絡接口層網際層網際層TCP/IPEthernet, 802.3, 等等TCP/IP支持支持所有標準的物所有標準的物理層和數據鏈理層和數據鏈路層協議路層協議DNS是TCP/IP的應用層協議之一。它利用了UDP傳輸層協議，端口為53。HTTPFTPSMTPTFTPDNSTelnetSNMP2123255369161TCP UDP應用層應用層傳輸層傳輸層TCP和和UDP都用都用端口端口(port)號號來識別應用層實體，根來識別應用層實體，根據據IP

2、地址和端口號就可以唯一地確定目的主機中某地址和端口號就可以唯一地確定目的主機中某個特定進程。個特定進程。port80域名空間分為若干層次：根域（頂級域）和次級域comabcxyzabcxy因特網 頂級域名服務器本地域名服務器 授權域名服務器 “樹根” 頂級域名服務器y本地域名服務器 授權域名服務器 本地域名服務器 授權域名服務器 的 IP 地址是什么？ Telnet Server Username:Password: InternetTelnet中國西安理工大學美國加州大學U N I V E R S I T YU N I V E R S I T Yl 不是指機器，不是指機器，是服

3、務器進程。是服務器進程。由于 PC 機的功能越來越強，用戶已較少使用TELNET了l 不是指機器，不是指機器，是服務器進程。是服務器進程。TCP連接連接TCP連接連接TCP連接連接TCP連接連接l 發信人運發信人運行用戶代理行用戶代理編輯郵件。編輯郵件。發件人的郵件服務器收件人的郵件服務器l 發送端郵件服務發送端郵件服務器收到郵件后，將器收到郵件后，將郵件放入郵件緩存郵件放入郵件緩存隊列，等待發送。隊列，等待發送。l 發送端郵件服務器中的發送端郵件服務器中的SMTP客戶進程發現郵件客戶進程發現郵件隊列中有待發送的郵件，隊列中有待發送的郵件，就與接收端郵件服務器建就與接收端郵件服務器建立立TCP

4、連接。連接。l 發送端的發送端的SMTP客戶進客戶進程使用程使用SMTP協議把郵件協議把郵件隊列中的郵件發送給接收隊列中的郵件發送給接收端的端的SMTP服務進程。服務進程。l 發送完后，關閉發送完后，關閉TCP連連接。接。l 接收端郵件服務接收端郵件服務器將收到的郵件放器將收到的郵件放入收件人的郵箱中。入收件人的郵箱中。l 收件人收信時，運行收件人收信時，運行用戶代理，用戶代理使用戶代理，用戶代理使用用POP3協議將用戶郵協議將用戶郵箱中的郵件下載到本地箱中的郵件下載到本地計算機。計算機。l 用戶代理利用用戶代理利用SMTP協議將郵協議將郵件傳送給發件人件傳送給發件人的郵件服務器。的郵件服務器

5、。TCP連接連接SMTP握手握手郵郵件件傳傳送送斷開斷開連接連接/連接到email服務器的25端口/發件人郵箱地址/收件人郵箱地址/郵件內容/郵件內容結束非 ASCII 碼7 位 ASCII 碼MIMESMTPMIMESMTP7 位 ASCII 碼7 位 ASCII 碼非 ASCII 碼用戶用戶Software、 ProgramDocumentsVideo，Audioftp Username: anonymousPassword: 匿名登錄FTPAnonymous FTP STCP數據傳送數據傳送控制控制FTP客戶端客戶端TCP數據傳送數據傳送控制控制FTP服務器端服務器端X21因特網因特網2

6、0Y由客戶端發起由服務器端發起3次握手01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp g

7、et rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.01 用戶要用 FTP 和遠地主機(網絡信息中心 NI

8、C 上的主機)建立連接。 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc

9、1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.02 本地 FTP 發出的連接成功信息。 01 ftp nic.d

10、02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PO

11、RT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.03 從遠地服務器返回的信息，220 表示“服務就緒”。 01 ftp 02 connecte

12、d to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command succes

13、sful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.04 本地 FTP 提示用戶鍵入名字。用戶鍵入的名字表示“匿名”。用戶只需鍵入 anonymous 即可。 01 ftp 02

14、connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT comman

15、d successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.05 數字 331 表示“用戶名正確”，需要口令。 01 ftp 02 connected to nic.ddn

16、.mil03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150

17、ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.06 本地 FTP 提示用戶鍵入口令。用戶這時可鍵入guest 作為匿名的口令，也可以鍵入自己的電子郵件地址，即耶魯大學數學系名為 xyz 的主機上的 abc。 01 ftp

18、 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11

19、200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.07 數字 230 表示用戶已經注冊完畢。 01 ftp 02 connected

20、 to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command success

21、ful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.“ftp”是 FTP 的提示信息。用戶鍵入的是將目錄改變為包含 RFC 文件的目錄。 01 ftp 02 connected to

22、 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful

23、.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.09 字符 CWD 是 FTP 的標準命令，代表 Change Working Directory。 01 ftp 02 connect

24、ed to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command succe

25、ssful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.10 用戶要求將名為 rfc1261.txt 的文件復制到本地主機上，并改名為 nicinfo。 01 ftp 02 conn

26、ected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command su

27、ccessful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.11 字符 PORT 是 FTP 的標準命令，表示要建立數據連接。200 表示“命令正確”。 01 ftp 02 con

28、nected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command s

29、uccessful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.12 數字 150 表示“文件狀態正確， 即將建立數據連接”。 01 ftp 02 connected to nic.

30、03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 1

31、50 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.13 數字 226 是“釋放數據連接”。現在一個新的本地文件已產生。 01 ftp 02 connected to 03 2

32、20 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII da

33、ta connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.14 用戶鍵入退出命令。 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: 07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261