Network Basics----Five protocols

• Summary of Knowledge points
  
  
• Serverresponseclient specific transfer data process for Web page requests
  

  1. The data to be transmitted is the HTML page of the Web server.
  2. Apply protocol HTTP header before adding to HTML data. Message header information includes: The HTTP version number used by the server, and the status code that indicates that it includes information sent to the network client.
  The 3.HTTP Application layer protocol sends HTML-formatted Web page data to the transport layer.
  The TCP Transport layer is used to manage sessions between the network server and the client. Before the 4.IP information is added to the TCP information. IP specifies the appropriate source and destination IP addresses. This information constitutes an IP message. 5. After the Ethernet protocol is added to both ends of the IP message. The data link frame is formed. The above frames are sent to a recent router on the path to the network client.
  The router removes the Ethernet information and observes the IP packets. Determine the best path to insert the message into a new frame. and sent to the target path next to a neighboring router. Each router is removed and the new data link layer information is added before forwarding.
  6. Data is transmitted over the Internet, including media and intermediary equipment. The 7.client receives a data link frame that includes data. Handles each layer of protocol headers, and then removes the protocol headers in the reverse order of accession. First, the Ethernet information is processed and removed. The IP protocol information is followed. The next TCP message, and finally the HTTP message.
  8. Afterwards. Pass the Web page information to the client Web browser software.

• Special handling of data transmission (encapsulation and parsing)
  

  Encapsulation encapsulation refers to the process of adding Additional Protocol header information to the data prior to transmission.
  In the vast majority of data communication processes, the source data will be encapsulated in a number of protocols before transmission.
  When a message is sent over the network. The protocol stack on the host operates from top to bottom.
  In the case of network server, the HTTP Application layer protocol sends HTML-formatted Web page data to the transport layer, and the application layer data is divided into TCP segments. Each TCP segment is labeled. Called the header, which indicates to which process the receiver should receive this message. The same time also includes information that allows the recipient to reorganize the data according to the original format.
  The transport layer sends the Web page HTML data to the network layer and runs the IP layer protocol.
  The entire TCP segment is encapsulated as an IP packet, which is the IP header tag. The IP header includes the source and destination IP addresses, as well as the information necessary to send the message to the destination address.
  After that, the IP packets are sent to the access layer, encapsulated with a frame header and a frame tail. Each frame header includes a source and destination physical address.
  The physical address uniquely specifies a device on the local network. The end of the frame includes error correction information. Finally, the server NIC transmits the bit encoding to the media.
  

  Unpacking the receiving host in the opposite way is called unpacking. The solution encapsulation is that the receiving device removes a layer or multilayer protocol process head. Data moves up in the protocol stack until the end of the application layer together with the unpack

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Network Basics----Five protocols