??www ?? www.sina.com.cn

1
?????????

• ????

2
2.1 ????????

• ??www ?? www.sina.com.cn
• ??email?? mail.163.com
• ??ftp?? ftp.tsinghua.edu.cn

3

• ???????????.????????
• ???????ftp????????ftp.tsinghua.edu.cn

4

• 2.1.1 ??????????
• ????(Domain Name)?????????????????????,??????????
  ?????

???????????
5
?????
Sina . Com . cn
?????? ????,? ?????? ?????
? ? ?
?????
?????
??
??
??
6

• ?????????
• Com ????
• Edu ????
• Gov ????
• Mil ????
• Net ????????
• Org ?????
• Int ????
• Country Code ??

7

• ?????????
• (1)????????
• 1,26?????
• 2,10??????
• 3,(???????)
• (2)??????????
• 1,?????????????
• 2,????????????????(????CN???,???????????20??
  ??)

8

• ???????
• Icann????????????
• Cnnic??????????

9

• ????www.cnnic.net.cn
• ????????????????????????
• ??????????????,?????????

10
??????????????????????????????????????????

• ??(?????????????)
• A.???????????cnnic????
• B.???chinese china cn national??????,?????
  ????????
• C.????????????????,?????????
• D.???????????,??????????????????,??????????

11

• ?????
• ?????????????????????,???????????????????,???????
  ??????????????????????(CNNIC)??,???????
• (1)??????
• (2)IP????
• (3)???????
• (4)?????????
• (5)????????????
• (6)???????????

12

• ?????
• ??????????????????????????????
• ??1,??ICANN??,??????ICANN????http//www.icann.org
  
• 2,??CNNIC??,(??????????????????)
  ?http//www.cnnic.net.cn
• 3,????????,??????.CN????????

13
??

• ???????
• Icann????????????
• Cnnic??????????

14
?????,????????( )
D

• A ftp..net.cn
• B ftp..ac.cn
• C www..ac.cn
• D www..edu.cn

15
B
???.gov????( )

• A ????
• B ????
• C ????
• D ????

16
2.2 IP??????

• ??2002?7?,????????????????????,??????????????????
  ?????IP?????,????????
• ????????????????

17

• ??2 ????????IP???????????????????TCP/IP?????,???
  ???????cmd,ipconfig.

18

• IP?????
• ????????????????,??????????????????,?????????
  ?,????????IP??,??????????????????????????

19

• ??1?????????,????
• www.sohu.com
• 61.135.132.12
• ????????????

20
Ip?????
192 . 168 . 5 . 48
11000000 10101000 00000101 00110000
32?
4?8????????
21
Ip?????
0 8
16 24
32

• 0 ???? ????
• 0 ????
  ????
• 1 1 0 ????
  ????

A? B? C?
A?B?C????? ????D?E
????
Ip??
????
22
11000000 10101000 00000101 00110000
192 . 168 . 5 . 48
C?
23
IP????????
???????????????????? ???A?B?C ??IP??????????????
24

• A?,????????????????,?????????????
• B?,??????????,??????????
• C??????????,????????
• ?????????????,
• D??E?,D??????????????,E????????

25

• IP?????????????????4??????IP??,???????????????,??
  ?????????????????,??,????IP??????,??????,???????C?
  ??,A,B??????

26

• ??3,??CNNIC??http//www.cnnic.net.cn??IP?????????
  ?,??????IP??,????????

27
Ip???????

• cnnic

28
??Ip?????
0 8
16 24
32

• 0 ???? ????
• 0 ????
  ????
• 1 1 0 ????
  ????

A? B? C?
A? B? C?
0-126 128-191 192-
??61.88.129.70 145.69.78.36
211.90.88.129
29
???
????

• 1?????IP?????????? ( )
• IP???????????????
• ?????????,IP????????
• 202.112.139.140??B???
• A?IP???????????????

C
30

• 2??????,???IP??? ( )
• 126.96.2.6
• 190.256.38.8
• 203.113.7.15
• 203.226.1.68

B
31

• 3?IP??126.168.0.1?????IP??( )
• D?
• C?
• B?
• A?

D
32

• 4?IP???????????????,????????? ( )
• ???IP??????????
• ???????????IP??
• ??IP??????????
• ??????????IP??

B
33
2.3 ???????????

• ???????????,??????,?????????????,?????,???????
  ??????

34

• ????????
• (internet server provider,ISP)
• ??????
• ???????????
• ????
• ????

35
??????????

• ????????Modem????   ISDN ??????   ADSL???????? 
  
• ??????Cable Modem????    DDN??????    ?????? 
• ??????GPRS ????   ????
• ????????????

36

• ??????????

1?IP????? 2??????????? 3???DNS???
37
??IP?????

• ???????,?????????????????
• IP???????
• (1)????????????IP??,?????,????IP???
• (2)?????????IP???????????,?????IP??,????????

38
????????????

• ??(Gateway)?????????????????,??????????????,??????
  ??????????
• ???????,???????
• ?????
• ?????IP??,????????????????,??????????????IP??,????
  ??,????????

39

• ????? ????????
• ?????????
• (1)???????????????,??????????????,?????????????
  ???
• (2)??????????????
• (3)??????????????????????

40
????

• ?????NAT,?????
• ??????????????

41

• NAT
• Short for Network Address Translation, an
  Internet standard that enables a local-area
  network (LAN) to use one set of IP addresses for
  internal traffic and a second set of addresses
  for external traffic. A NAT box located where the
  LAN meets the Internet makes all necessary IP
  address translations.
• NAT serves three main purposes
• Provides a type of firewall by hiding internal IP
  addresses
• Enables a company to use more internal IP
  addresses. Since they're used internally only,
  there's no possibility of conflict with IP
  addresses used by other companies and
  organizations.
• Allows a company to combine multiple ISDN
  connections into a single Internet connection.
• NAT(??????),???????????????????????NAT????????
  Intranet?????????????????,???????????Internet(IPv4
  )???

42
????DNS???

• ???????IP????,????,???,?????????,???????IP?????,??
  ???????????????,????????????

43

• DNS?????????DNS(Domain Name System)???????????.
• ???????????????????????ip??.
• ??????????www.abc.com???????61.145.112.141

44
??????????????IP??

• DNS?????,??????????
• ??????????????www.cnnic.net.cn,?????????????,????
  ?????????????
• ??? ??????????????,?????????,???????,????????????
  ?????????
• ????????????????,??????????????????????,?????????
  ????????????????(????)???????????
• ?????????????????????????,?????????????????,?????
  ??,??????????????????
• ????????,??????????
• ?????????????????????,???????,?????????????

45
????

• ???????????
• ????????????

46
??
4
???A
?????
??www.abc.cn
1
ISP DNS ??? B
(root) DNS ??? C
2
4
??
????
(CNNIC .CN) DNS??? D
??
?
3
(abc.cn) DNS ???
47

• A?????1.1.1.1   B ISP DNS ???2.2.2.2   C (root)
  DNS ???8.8.8.8    D (CNNIC .CN) DNS??? 5.5.5.5 
   E (abc.cn) DNS ??? A ?DNS?????? B???(1)A
  ????www.abc.cn , ------ gt  A ???? B  ----gt(2) B
  ?????????www.abc.cn ???, -----gt(3) ???www.abc.cn
  ???,???????? A ???(1)A ????www.abc.cn ,
  ------ gt  A ???? B  ----gt(2) B
  ?????????www.abc.cn ???, -----gt(3) ?? www.abc.cn
  ???----gt(4)?B???C ".CN ?????" ------gt(4) C??B
  ??D ??? ---gt (5) B??????????".CN"?????D "abc.cn
  ????" ------gt(6) D??B "??E ????" -----gt B ???E
  "www.abc.cn ???????" ----gt(7) B ?????????A
  ????????

48
????

• ?? k12??
• www.k12.cn ?? ????????
• ?? www.edu.cn(???????????)