wireshark Packet Analysis data Encapsulation
Data encapsulation ( data encapsulation PDU osi seven-layer reference model, Each layer is primarily responsible for communicating with peers on other machines. The procedure is in the Protocol Data unit ( PDU ), where each layer of PDU wireshark packet analysis of the actual combat details Tsinghua University Press
to help users understand the data encapsulation process more clearly, an example is given below to illustrate the process. Suppose a corporate LAN uses Ethernet, and when An employee downloads a file from an FTP server on a local area network, the file is transferred from the FTP server to the employee host 1.17 shown in this article selected from wireshark data Packet Analysis of the actual combat in Tsinghua University Press .
Figure 1.17 TCP/IP transmission of data in the
in the figure 1.17 in which FTP The server acts as the sending side of the data, and the employee hosts as the receiving end of the data. The following sections describe the data sending and receiving processes respectively.
1. data transmission processing process Data Encapsulation Protocol Data unit Package Wireshark packet Analysis
( 1 The application layer gives the data to the transport layer, and the transport layer adds TCP the control information (called TCP header), this data unit is called a segment ( Segment ), the process of adding control information is called encapsulation. Then, give the segment to the network layer.
( 2 ) the network layer receives segments, plus ip head, this data unit is called a package ( packet ). The package is then handed over to the data link layer.
( 3 ) The Data link layer receives the packet and adds MAC head and tail, this data unit is called FRAME ( Frame ). Then, give the frame to the physical layer.
( 4 The physical layer converts the received data into a bit stream and then transmits it in the network cable.
2. data receive processing process Data Encapsulation Protocol Data unit Package Wireshark packet Analysis
( 1 The physical layer receives the bit stream and passes the data to the data link layer after processing.
( 2 The Data link layer transforms the received data into a data frame and then removes MAC head and tail, this process of removing control information is called unpacking, and then the package is delivered to the network layer.
( 3 ) The network layer receives the packet and then drops IP head and then hand the segment to the transport layer.
( 4 ) The transport layer receives the segment and then drops TCP head, and then hand over the data to the application layer.
From the above transmission process, the following points can be summed up. As shown below:
( 1 the method of data processing by the sender is from the high-level to the bottom-level, and encapsulates each layer.
( 2 the method of data processing by the receiver is from the bottom to the upper layer, and then encapsulates it by layers.
( 3 each layer of the receiver takes away only the data that is meaningful to that layer, or each layer can only process data from the same layer of the sender, and then pass the rest to the previous layer, which is the concept of peer -to-layer communication This article is selected from Wireshark Data Packet Analysis of the actual practice Tsinghua University Press Data Encapsulation Protocol Data Unit Package Wireshark packet Analysis .
Wireshark Packet Analysis Data encapsulation