最近在寫tcp/ip的下位機，所以學了不少關于網絡和協議的東西。總體上來說，很復雜。不過還是有據可循的。
這是通過wireshark抓包得到的
這是一個簡單的ping命令，得到的數據。
Frame 207: 74 bytes on wire (592 bits), 74 bytes captured (592 bits) 線路上傳輸了74字節，實際接收74個字節
Arrival Time: Jan 1, 2000 08:09:10.326362000 中國標準時間 時間
Epoch Time: 946685350.326362000 seconds 包間隔時間
Time delta from previous captured frame: 0.087277000 seconds
Time delta from previous displayed frame: 0.087277000 seconds
Time since reference or first frame: 12.473428000 seconds
Frame Number: 207
Frame Length: 74 bytes (592 bits) 幀長度
Capture Length: 74 bytes (592 bits) 捕獲長度
Frame is marked: False
Frame is ignored: False
Protocols in frame: eth:ip:icmp:data 協議層級
Coloring Rule Name: ICMP 包含協議
Coloring Rule String: icmp || icmpv6
Ethernet II, Src: D-Link_60:3b:42 (f0:7d:68:60:3b:42), Dst: Tp-LinkT_4f:6f:f2 (94:0c:6d:4f:6f:f2)
源mac地址 目標mac地址
Destination: Tp-LinkT_4f:6f:f2 (94:0c:6d:4f:6f:f2)
Address: Tp-LinkT_4f:6f:f2 (94:0c:6d:4f:6f:f2)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
. ... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Type: IP (0x0800) ip類型
Internet Protocol, Src: 192.168.1.111 (192.168.1.111), Dst: 192.168.1.1 (192.168.1.1)
源ip地址 目標ip地址
Version: 4 版本號
Header length: 20 bytes 頭字節長度
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00) 差分服務字段
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 60 IP包長度
Identification: 0x31e7 (12775) 標志字段 不一樣，具體為什么不知道
Flags: 0x00 標記字段
Fragment offset: 0 分段偏移
Time to live: 64 生存期
Protocol: ICMP (1) 包內封裝協議
Header checksum: 0xc519 [correct] 頭校驗
Source: 192.168.1.111 (192.168.1.111) 源ip
Destination: 192.168.1.1 (192.168.1.1) 目標ip
Internet Control Message Protocol
Type: 8 (Echo (ping) request) 類型：請求
Code: 0 代碼：0
Checksum: 0x495c [correct] 校驗
Identifier: 0x0300 標識碼
Sequence number: 256 (0x0100) 序列碼，應該是ping一次加一次
Sequence number (LE): 1 (0x0001)
Data (32 bytes) 數據
Data: 6162636465666768696a6b6c6d6e6f707172737475767761...
Length: 32
源mac地址 目標mac地址 ip類型 版本與字節數
94 0c 6d 4f 6f f2 f0 7d 68 60 3b 42 08 00 45 00
Ip包長 標志段 標記 偏移 生存期 icmp包 頭檢驗 源ip
00 3c 31 e7 00 00 40 01 c5 19 c0 a8 01 6f
目標ip 類型 校驗 標識碼 序列碼 數據
c0 a8 01 01 08 00 49 5c 03 00 01 00 61 62 63 64 65 66
67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76
77 61 62 63 64 65 66 67 68 69