A network address planning table
| source address |
Destination address |
Remark |
| 172.24.56.170 |
183.232.231.172 |
Cmd |
| 172.24.56.170 |
120.233.76.210 |
Cmd |
two. Configure the source address
Open the computer "Control Panel", click "Network and Sharing Center", click "Ethernet", click "Properties", select "Internet Protocol Version 4", click "Properties" proceed as follows. Connectivity Test: open a Web page, can be connected to the network.
three. The application layer analysis
Open cmd window, of ping through Baidu, cool web, results as shown below:
four. Transport Layer
- TCP three-way handshake / establish a connection:
(1) The first handshake
Source address ( 172.24.56.170 ) At 296 during times TCP sent a connection request to the address Baidu segment, which bit synchronization header of the SYN =. 1 .
(2) The second handshake
Baidu of TCP after receiving a connection request segment, the ACK =. 1 , at the same time sends a connection request to the source address, so that the SYN =. 1 .
(3) third handshake
Confirmation given source address to the destination address, so that ACK = 1, then the connection is established.
- TCP handshake / release connection
(1) First wave: the client sends a TCP , and then stops sending data, actively closed TCP connection. FIN and ACK set 1 , as shown below No. Seq = 753 , the acknowledgment number Ack = 1
(2) Second wave: server receives FIN after a back the ACK, acknowledgment received sequence number plus 1 i.e. the Ack = 155 , Seq = 1.
(3) Third Wave: server closes the connection with the client sends a FIN and the ACK , number Seq =. 1 , the Ack = 169.
(4) Fourth wave: the client receives the server sends the FIN , the back ACK acknowledgment to confirm the received sequence number plus 1 i.e. the Ack = 1.
- UDP protocol
UDP efficient but unreliable ; UDP no correction function, packets are lost during transmission is not responsible for the retransmission ; UDP can not control the flow rate ; UDP is typically used less total packet communication, instant messaging, broadcast communication .
UDP header . 8 bytes, can be selected from blue to clearly see FIG portion; indicated by the figure can be seen, the source port number 60594 , a destination port number 535 , UDP header and a data length 310 , UDP checksum and is 0x 8B10 .
Fives. Network layer analysis ( IP packets, ARP protocol, ICMP protocol)
1.IP packet analysis:
IP packets first paragraph: 4 indicates the version, header length of 20bytes , 0x00 is differentiated service, total length 40 .
IP packets second paragraph: 0xf557 bits logo, Flags as a symbol. Transfer sheet is 0 , which is the initial identification ip sheet transfer.
2.ARP protocol analysis
six. A data link layer ( the MAC address analysis)
MAC as an address within a frame interface to identify the LAN to which the other physical interface to which is connected from . Thus , with multiple network interfaces with a host or router having a plurality of link layer addresses associated , as they having a plurality of IP addresses the same . Note that , the link layer does not switch MAC address .
MAC address is also known as LAN address , the physical address .
MAC address length is . 6 bytes ,, a total of 2 ^ 48 possible MAC address .
2. The Ethernet MAC frame format
( . 1 ) the IEEE 's 802.3 standard
(2) DIX Ethernet V2 standard, Ethernet V2 standard
Seven. to sum up
This time the job has given me a lot of harvest, been through a lot, so I can not forget. Finally, no matter how many points can get a job, no matter what the end result will eventually be the result, I think the job is worth, which is entirely on my own, counseling students to view the data, and then hands-on.
Personal experience to learn tcp content of the message, made me realize what is practice makes perfect, in this task, I think the card is the longest IP address configuration, computer configuration has been bad, then good job and no network, and finally with the help of students, to solve this problem, during the network layer and link-layer packet capture, according to the standard to crawl. Through this capture operation, so I IP have a more in-depth understanding of the communication courses, textbooks but not necessarily comprehensive, practical operation of only yourself, only better learning results . I also understand the importance of unity is strength, teamwork, but also made me aware of their own deficiencies, but also ignited my desire for knowledge. The second is about the analysis of the message, this reference book and found no error control example of the right, to deepen understanding of the experiment, and so on.