计算机网络概论

Size: px

Start display at page:

Download "计算机网络概论"

脂智
7 years ago
Views:

1 TCP/IP

2 1. 2. IP 3. TCP/IP 4. IPv6

3 1 TCP/IP Application Presentation Session Transport 3 Network 2 1 Data Data link link Physical

4 2 IP IPv4

5 2.1 IPv4

6 2.1 IPv4

7 2.1 IPv4

8 2.1 IPv4-

9 2.1 IPv4-

10 2.1 IPv4-

11 2.1 IPv4-

12 2.1 IPv4- IETF A B C Internet Internet

13 2.1 IPv4- Internet IP a1.b1.c1.d1 a2.b2.c2.d2 an.bn.cn.dn NAT a3.b3.c3.d3 x1.x2.x3.x4 x1.x2.x3.x4 x1.x2.x3.x4

14 2.1 IPv4-48bits Ipconfig /all

17 2.2 IPv4 Network Mask Def. A B C

18 2.2 Sub-Network Mask Hostid Netid N 1+ M 0=32 IP =

19 2.2 Sub-Network Mask

20 xxxxxxx xxxxxxxxx xxxxxxx

22 A B C ip ip

23 3 TCP/IP : ICMP IGMP ARP RARP : UDP TCP : SMTP/POP HTTP DNS FTP

26 3.1 ARP/RARP ICMP IGMP

27 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Version (4 bits): tells that this is IP Version 4 (IPv4)

28 IPv4 header structure Version Version Time-to-live Time-to-live IHL IHL Type Type of of Service Service Identification Identification Protocol Protocol Options Options Total Total length length of of IP IP datagram datagram Flags Flags Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Header length (4 bits) is needed since Options + Padding can vary in length. Options Security (packet classification), Strict source routing (the whole routing list), Loose source routing (the mandatory routing list), Record route (record the IP address of each hop), Timestamp (record the IP address and timestamp of each hop).

29 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram ToS = Type of Service (8 bits) is used for QoS management purposes. The first 3 bits of TOS indicate priorities, 0 being low (normal packet) and 7 being high (network control packet); the next 3 bits indicate service types, being delay, throughput, and reliability; the last 2 bits are reserved. Source could use service type bits to indicate the routing metrics to be used.

30 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Datagram length (16 bits): since this field is 16 bits long, the IP datagram can contain up to 2 16 = bytes (in theory). Most routers, however, cannot handle such large datagrams.

31 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification All fragments contain the same number Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Has value zero Destination Position of Destination IP IP address address in last fragment in Padding fragment original datagram Padding Payload Payload of of IP IP datagram datagram IP fragmentation: a large IP datagram may be fragmented (in any router along the path) and will be reassembled at the destination. Flags: 1st bit reserved; 2nd bit DF, 0 fragment yes, 1 fragment no; 3rd bit MF, 0 last fragment, 1 more fragment. SEU 31

32 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Time-to-live (8 bits): this number is decreased by one in each router along the path. If number zero is reached in a router, IP datagram is discarded and router sends an ICMP message (TTL expired) to the source of the datagram.

33 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Starts here... Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Payload Payload of of IP IP datagram datagram Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Protocol field (8 bits): describes which higher layer protocol is used (TCP, UDP, SCTP...). The header of this upper protocol is located at the beginning of the IP datagram payload. e.g. 6 TCP, 17 UDP, 1 ICMP, 89 OSPF, etc. SEU 33

34 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Header checksum (16 bits): used for error control (if used, routers along the path have to recalculate the checksum). This kind of error control is not used in IPv6 (since the same error control function is offered by TCP - and even UDP). SEU 34

35 IPv4 header structure Version Version IHL IHL Time-to-live Time-to-live Identification Identification Type Type of of Service Service Protocol Protocol Options Options Flags Flags Total Total length length of of IP IP datagram datagram Fragment Fragment offset offset Header Header checksum checksum (for (for error error control) control) Source Source IP IP address address Destination Destination IP IP address address Padding Padding Payload Payload of of IP IP datagram datagram Source and destination IP address (32 bits each): note that these addresses are not changed in routers along the route. SEU 35

36 IP

37 (ARP/RARP)

38 ARP/RARP

39 ARP

40 ARP 1 IP 0800

41 ARP

42 example broadcast unicast

43 ARP

47 ARP -cache

48 C:\Documents and Settings\Administrator>PING Pinging with 32 bytes of data: Reply from : bytes=32 time<1ms TTL=128 Reply from : bytes=32 time<1ms TTL=128 Reply from : bytes=32 time<1ms TTL=128 Reply from : bytes=32 time<1ms TTL=128 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms C:\Documents and Settings\Administrator>ARP -D C:\Documents and Settings\Administrator>ARP -A No ARP Entries Found C:\Documents and Settings\Administrator>ARP -S C:\Documents and Settings\Administrator>APR -A 'APR' C:\Documents and Settings\Administrator>ARP -A Interface: x10005 Internet Address Physical Address Type static C:\Documents and Settings\Administrator>PING

49 sniffer

50 Arp A: ip AA:AA:AA:AA:AA:AA B: ip BB:BB:BB:BB:BB:BB C: ip CC:CC:CC:CC:CC:CC

51 Arp C 2. ip ip , MAC BB:BB:BB:BB:BB:BB A A arp 4. arp C ip-->mac ip mac telnet

52 ARP ip mac ip+mac mac-->ip

53 ARP Proxy

54 RARP

55 RARP

56 RARP

57 ARP LAN IP

58 3.1.2 ICMP

59 ICMP

60 ICMP

61 ICMP

62 ICMP

63 ICMP

64 ICMP ICMP ip 8 ICMP

65 ICMP A R1 R2 R3 B ICMP

66 ICMP

67 ICMP

68 ICMP

69 ICMP ID SN

70 ICMP ping

71 TRACEROUTE LINUX TRACERT WINDOWS sniffer

72 3.1.3 IGMP Multicast Internet Group Management Protocol RFC1112

73 IGMP

74 1 0 2

75 NTP.

76 e ~ e.7f.ff.ff ID 32

78 3.2 TCP UDP

79 3.2

80 3.2.1 TCP

81 TCP I P I P TCP TCP

82 Tcp TCP IP IP

83 Tcp

84 TCP Connect and discon

85 TCP Connect and discon syn syn ISN+1 ISN

86 TCP Connect Reliability

87 TCP Connect and discon

88 TCP Connect and discon

89 TCP Connect and discon

90 TCP Connect and discon TCP

91 TCP How to Get RTT

92 TCP Max-Send-Segment MSS=Min MTU SMSS RMSS Sniffer

93 3.2.2 UDP

94 TCP/UDP

95 TCP/UDP

96 TCP/UDP

97 UDP

98 3.3 http DNS FTP

99 3.3.1 Mail

100 3.3.1 Mail Protocol SMTP Postel J B.Simple Mail Transfer Protocol. RFC821[EB/OL]. rfc/ rfc0821.txt POP Myers J. Post Office Protocol - Version 3.RFC1939[EB/OL]. l939.txt

101 3.3.1 Mail Theory SMTP POP Foxmail Outlook SENDMAIL QMAIL

102 3.3.1 Mail Format rfc822 Rfc 822

103 3.3.1 Mail Format-MIME RFC1341 (RFC2231 RFC2646 ) MIME Multipurpose Internet Mail Extensions

104 3.3.1 MIME

105 3.3.1 MIME base64

106 3.3.1 MIME base64

107 3.3.1 MIME Quoted-printable

108 3.3.1 MIME Quoted-printable

109 3.3.1 Mail Format

110 3.3.1 Mail Format

111 3.3.1 SMTP Connect 25 Connection establishment

112 Message transfer

113 Connection termination

114 3.3.1 Pop-post office protocol

115 pop3

116 3.3.1 SPAM

117 SPAM

118 SPAM

119 SPAM

120 SPAM Black Menu White Menu rule

121 SPAM

122 SPAM

123 SPAM

124

125 HTTP Hypertext Transfer Protocol

126 HTTP Paradigm

127 HTTP Message types

128 HTTP Request Message

129 HTTP Request Line

130 HTTP GET Method HEAD POST PUT DELETE

131 HTTP GET

132 HTTP POST

133 HTTP HEAD

134 HTTP URL

135 HTTP Response message

136 HTTP Status line

137 HTTP STATUS CODE

138 HTTP

139 GET

140 HTTP HEAD

141 HTTP POST

142 Web ( Web1.0

143 Web

144 WWW world wide web

145 WWW world wide web

146 Hypertext

147 Brower structure

148 Web

149 html xml xhtml

150 html xml xhtml

151 Web phishing

152 Web phishing

153 APWG SPONSORS

154 APWG Global Research Partners:

155 S1:

156 S2 Visible link: cmd=_login-run Actual link to: Phish site IP:

157 Web phishing handling Html image

158 Web phishing handling

159 Web phishing handling

160 3.3.3 DNS

161 DNS g e t h o s t b y n a m e g e t h o s t b y a d d r

162 DNS

163 DNS

164 DNS

165 DNS

166

167

168 DNS

169 DNS 0-std query ip 1-recursive 0-iterative 1-inverse query 2-server query query states 0-query 1-response Authoritative answer

170 DNS types

171 Format of Query & Answer

172 What protocol-udp/tcp Client (resolver) Client (resolver) Udp/tcp Udp/tcp Port:53 Main server tcp additional server

173 Name length Domain name Name=label.label label. Length of label <=63 octet Length of name <=255 octet

174 DNS domain name structure

175 DNS Query Process Iterative in which the server refers the client to another server and lets the client pursue the query. Recursive in which the first server pursues the query for the client at another server. Both approaches have advantages and disadvantages, but the iterative approach is preferred for the datagram style of access. The domain system requires implementation of the iterative approach, but allows the recursive approach as an option.

176 Instance of iterative query

177 Instance of recursive query User MIT DNS edu DNS root cn DNS Edu.cn DNS Seu.edu.cn DNS MIT DNS edu DNS root cn DNS ibm edu.cn DNS seu.edu.cn DNS User com root edu cn User MIT com seu edu pku www ftp gov ptt tsinghua

178 3.3.4 Ftp rfc0959

179 Ftp user-ftp process A set of functions including a protocol interpreter, a data transfer process and a user interface which together perform the function of file transfer in cooperation with one or more server-ftp processes. The user interface allows a local language to be used in the command-reply dialogue with the user server-ftp process A process or set of processes which perform the function of file transfer in cooperation with a user-ftp process and, possibly, another server. The functions consist of a protocol interpreter (PI) and a data transfer process (DTP)

180 Ftp PI The protocol interpreter. server-dtp The data transfer process, in its normal "active" state, establishes the data connection with the "listening" data port. user-dtp The data transfer process "listens" on the data port for a connection from a server-ftp process.

181 Ftp FTP model

182 Ftp Two connections control connection The communication path between the USER-PI and SERVER-PI for the exchange of commands and replies. This connection follows the Telnet Protocol. data connection A full duplex connection over which data is transferred, in a specified mode and type. The data transferred may be a part o a file, an entire file or a number of files. The path may be between a server-dtp and a user-dtp, or between two server-dtps. Normally the client active the control connection the server active the data connection

183 Ftp PORT ADDRESS Both the user and the server DTPs have a default data port. The user-process default data port is the same as the control connection port,the server-process default data port is the port adjacent to the control connection port (i.e., 21-1=20). the user can set new data port.

184 Ftp

185 ftp

186 ftp

187 ftp 3-4byte

188 ftp restart marker marker get put restart 130 CuteFTP Log FTP Netants FTP SIZE.job

189 4 IPV6

190 IPV6

191 IPV6

192 ipv6

193 IPV6

194 IPV6

195 Windows xp Linux ipv6 install

196 IPV6 Tunnel Ipv4(1)-v6(1) Ipv4(2)-v6(2) Ipv4(3)-v6(3) Ipv4(4)-v6(4) Ipv4(n)-v6(n) How to realize? Ipv4(1)-v6(1) Ipv4(2)-v6(2) Ipv4(3)-v6(3) Ipv4(4)-v6(4) Ipv4(n)-v6(n)

197 IPV6 Add & Protocol transformation

198

199

200 END of TCP/IP

財金資訊-80期.indd

財金資訊-80期.indd IPv6 / LINE YouTube TCP/IP TCP (Transmission Control Protocol) IP (Internet Protocol) (node) (address) IPv4 168.95.1.1 IPv4 1981 RFC 791 --IP IPv4 32 2 32 42 IP (Internet Service Provider ISP) IP IP IPv4