Conceptual understanding-Broadcast domains and conflict domains, broadcast storms, OSI

Conflict domains: Only one device can send information within the same time. Switches can narrow the scope of a conflict domain, and each port that is exchanged is a conflict domain. Broadcast domain: If a site emits a broadcast signal, all devices that receive this signal are called a broadcast domain. Broadcast storm: When broadcast data flooding the network can not be processed, and occupy a large amount of network bandwidth, so that normal business can not run, or even completely paralyzed, this happened "broadcast storm." OSI7 layer protocol: Is the interface between the actual application program. The layer is a converter that provides encoding and conversion capabilities. Tasks such as data compression, decompression, encryption, and decryption are all related to the presentation layer. Responsible for establishing, managing, and terminating sessions between presentation layer entities, as well as controlling conversations between devices or nodes. Fragment the data and reorganize it into a data stream. Manages device addressing, tracks the location of the device in the network, and determines the optimal data transfer path. Provides physical transmission of data and handles error notification, network topology, and traffic control. There are two functions: send and receive bits.

The application, presentation, and session tiers belong to the upper layer and are responsible for communication between the user interface and the application. The Transport layer provides segmentation, sequencing, and virtual circuits. The network layer provides the logical network addressing and the function of routing in the Internetwork. The data link layer provides the ability to encapsulate data into frames and place them on a network medium. The physical layer is responsible for encoding the received 0  and 1  into digital signals for transmission in the network segment. The process of two-host communication, from the sender (hereinafter referred to as a) to the receiver (hereinafter referred to as B), belongs to the->1 layer (the physical layer) from the 7 layer (the application layer) encapsulated, then transferred to the remote, and then from the 1 layer (physical layer)->7 layer (application layer) to unpack the process. 1,   When a opened QQ this software, quite to reach the application layer, because the software will be based on your operation to mobilize the bottom of the machine hardware work. 2,   When a to QQ this software Chat window input information, issued, QQ will save this information in the local chat record file Msgex.db (generally saved in the QQ directory with your QQ number for the folder). encoding/saving some kind of information in some format, which can be understood as the presentation layer. 3,   When a open chat window with B, enter information, press the "Input" button, the user's operation is over, the rest is the machine's own operation. Before the actual transmission QQ will first establish a and B session connection, only to really start transmitting information/data (you can understand the borrowing transfer file understanding: You send the file to each other, to wait for the other party to press receive, only calculate the session, and then start the transmission. This is the conversation layer. 4. After the   session is established, a message will be chopped, such as a send "did you eat dinner?" The transport layer will chop this sentence into "You" "Eat" "" Rice "" no "" have "6 data segments, tag number used by the port number, and then ready to send out. 5,   connected to a layer, the information has not been sent out, at this time in the network layer to do routing, it can be understood that, from a home, can be "Unicom", "Telecom" "mobile" 3 network one to B home. The network layer is responsible for routing (based on the methodology of link quality, bandwidth, overhead, etc.) based on the route protocol. Suppose the last choice of 2, may be a-> unicom->b send "You" "Eat" "" "3 Data segments,a-> Telecom->b send" Rice "" no "" have "3 data segments. Select the road, this layer to mark the IP header, Baotou main content is the source IP address, the destination IP address, the use of what protocol. Where the source, destination IP equivalent to the time you send a letter to send and receive the address and postal code, mark the departure of the sender and receiver. The agreement corresponds to the exact language in which the letter was written. (Only guarantee 2 end use the same language, can ensure communication up, otherwise you write to aunt in English, how can aunt understand? ) 6,   then to the data link layer, the data link layer is mainly responsible for the same subnet within theCommunication. For example, a, B is connected to the same two-layer switch, it belongs to the same subnet, then the data frame of the communication room is not required through the network layer (that is, the three-layer switch or router), directly in the two-layer switch on the past. This layer is the MAC address of the frame head, for the above communication process, is the data frame hit a machine Mac with a Gateway Mac. The work on this floor is complete. 7,   The last layer, after the above chop, after the end of each layer labeled 6 data frames, the physical layer will they translate 6 paragraphs 0, 1 of the bit stream, and then through the fiber, copper cable transmission. 8,   When the bitstream is transmitted to the far end, then the machine of B follows the 1~7 of the above steps in the opposite direction (that is, the physical layer to the application layer). is to read the label in layers, transfer it to the corresponding object labeled by the tag, remove the label, and then read the previous layer of labels until the last B's application can read the data entered by a toward the application.

Conceptual understanding-Broadcast domains and conflict domains, broadcast storms, OSI