【正文】 行一系列功能的軟件 , IP軟件決定如何創(chuàng)建數(shù)據(jù)報及如何使數(shù)據(jù)報通過一個網(wǎng)絡(luò) ? IP software has 3 important information area IP軟件的三個重要信息域 – IP address: a unique 32bits address IP地址域 一個獨一無二的 32位地址 – Sub work mask: a 32bits information bits group, indicate which part of the IP address is work ID and which part is host Id 子網(wǎng)掩碼域 – Default gateway: an optional 32bits address, indicate a router. All packets send to other work will go to this router if no specific route for that work 缺省網(wǎng)關(guān)域 ? When sending data, IP get data from transport layer and send to work access layer 在發(fā)送數(shù)據(jù)時 , IP從傳輸層得到數(shù)據(jù) , 處理后送往網(wǎng)絡(luò)訪問層 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Version IHL[0] Service Type[1] Packet length (Include header and data)[2] ID FFlag[3] Fragmentation Offset TimeToLive Protocol[4] Header Checksum Source IP address Destination IP address Optional Fields (0 to many bytes) [1] bit02: priority bit3:Delay bit4:Throughput bit5:Reliability bit67:Reserved [2] Maximum size is 65535, default is 576 (512bytes data+ 64bytes header) [3] bit0:Reserved, must be 0 bit1(DF):0=allow 1disallow bit2(MF):0=last 1=more [4] 1:ICMP 2:IGMP 3:GGP 4:IP 5:ST 6:TCP 8:EGP 17:UDP 80:CLNP 88:IGRP 89:OSPF IP Data payload (Many bytes) Padding [0] scope 515, number of DWORD(32bits) notes:Byte(8bits) WORD(16bits) DWORD(32bits) IP Header IP的首標(biāo) IP Address IP地址 ? IP address consists of four dot separated numbers IP地址由四個被圓點隔開的數(shù)字組成 ? IP address just like house address IP地址好比住宅的地址 – Network ID like street name 網(wǎng)絡(luò)名好比街道名 – Host ID like house number 主機名好比門牌號 ? Each puter (node) should have a unique IP address 每臺計算機 (節(jié)點 )都應(yīng)有獨一無二的 IP地址 Binary Decimal 27 26 128 25 24 23 22 21 20 64 32 16 8 4 2 1 Hexadecimal 80 40 20 10 8 4 2 1 Binary Hexadecimal Decimal 0001 1 1 0010 2 2 0011 3 3 0100 4 4 0101 5 5 0110 6 6 0111 7 7 Binary Hexadecimal Decimal 1001 9 9 1010 10 A 1011 11 B 1100 12 C 1101 13 D 1110 14 E 1111 15 F 0000 0 0 1000 8 8 Binary Hexadecimal Decimal 8bits 0255 00FF 16bits 065,535 00FFFF 24bits 016,777,215 00FFFFFF 32bits 04,294,967,295 00FFFFFFFF 10bits 01023(1K) 20bits 01,048,575(1M) 03FF 0FFFFF Use Octet Address (1) 使用 8位組地址 (1) 10000000 128 Bin Dec 11000000 192 11100000 224 11110000 240 11111000 248 11111100 252 11111110 254 01111111 127 Bin Dec 00111111 63 00011111 31 00001111 15 00000111 7 00000011 3 00000001 1 80 Hex C0 E0 F0 F8 FC FE 7F Hex 3F 1F 0F 07 03 01 Bin Dec 11000000 192 01000100 68 00000011 3 10000101 133 Hex C0 44 03 85 Binary Hexadecimal 1 0 80 0 1 1 0 1 0 0 0 10 8 0 2 0 Decimal 128 0 0 16 8 0 2 0 10011010 154 9A Use Octet Address (2) 使用 8位組地址 (2) Address Class 地址分類 ? Theoretically 32bits IP address can support 4 billion nodes 理論上 32位的 IP地址能支持超過 40億個節(jié)點 ? IP Address have 5 classes 目前將 IP地址分為了 5類 ? Class A have 8 bits work ID A類地址有 8位表示網(wǎng)絡(luò)名 ? Class B have 16 bits work ID B類地址有 16位表示網(wǎng)絡(luò)名 ? Class C have 24 bits work ID C類地址有 24位表示網(wǎng)絡(luò)名 ? Class D is for multicast D類地址用于多點廣播 ? Class E is reserved for test work E類地址保留作測試用 00000000 00000001 0xxxxxxx 01111110 01111111 Network ID 0 1 2125 126 127 Decimal Local work First usable class A work Usable Class A works Last usable class A work Loopback or Local host Meaning Format 0xxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx Netmask 11111111 00000000 00000000 00000000 Network ID 0xxxxxxx 00000000 00000000 00000000 Host ID 00000000 xxxxxxxx xxxxxxxx xxxxxxxx Class A Address A類地址 10000000 00000000 10000000 00000001 10xxxxxx xxxxxxxx 10111111 11111110 10111111 11111111 Network ID Decimal Local work First usable class B work Usable Class B works Last usable class B work Broadcast Meaning Format 10xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx Netmask 11111111 11111111 00000000 00000000 Network ID 10xxxxxx xxxxxxxx 00000000 00000000 Host ID 00000000 00000000 xxxxxxxx xxxxxxxx Class B Address B類地址 11000000 00000000 00000000 11000000 00000000 00000001 110xxxxx xxxxxxxx xxxxxxxx 11011111 11111111 11111110 11011111 11111111 11111111 Network ID Decimal Local work First usable class B work Usable Class B works Last usable class B work Broadcast Decimal Format 110xxxxx xxxxxxxx xxxxxxxx xxxxxxxx Netmask 11111111 11111111 11111111 00000000 Network ID 110xxxxx xxxxxxxx xxxxxxxx 00000000 Host ID 00000000 00000000 00000000 xxxxxxxx Class C Address C類地址 Class D Format 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx Class E Format 11110xxx xxxxxxxx xxxxxxxx xxxxxxxx Description Multicast Group Address Description Reserved for test work, not exist Scope Scope Class D and Class E Address D類和 E類地址 Benefit of Sub 劃分子網(wǎng)的好處 ? Reduce collision 減少沖突 ? Support different work technology 支持不同的網(wǎng)絡(luò)技術(shù) ? Overe the limitation of work technology 克服網(wǎng)絡(luò)技術(shù)的極限 ? Improve security level 提高安全級別 ? Reduce broadcast impact 減少廣播的影響 ? Support Wide Area Network 支持廣域網(wǎng) Rules of Sub 劃分子網(wǎng)的規(guī)則 ? Rules 規(guī)則 – Sub mask begin after default class A/B/C mask 子網(wǎng)掩碼從標(biāo)準(zhǔn)的 A/B/C類地址掩碼之后開始 – Sub mask should have successive 1 子網(wǎng)掩碼必須是連續(xù)的 1 – Sub ID should not be all 0 or all 1 子網(wǎng)名不可全是 0或全是 1 – Host ID should not be all 0 or all 1 主機名不可全是 0或全是 1 ? Result 結(jié)果 – Class A IP have 21 kinds of sub mask A類地址有 21種子網(wǎng)掩碼 – Class B IP have 13 kinds of sub mask B類地址有 13種子網(wǎng)掩碼 – Class C IP have 5 kinds of sub mask C類地址有 5種子網(wǎng)掩碼 200 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 0 1 0 0 0 1 0 1 0 1 1 0 1 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 37 17 90 255 255 255 0 200 1