How many data exchange strategies or methods are there? What are they?

It is worth mentioning the NAT technology in the firewall, and the address translation can hide the IP address of the intranet, which many people regard as a kind of security protection, thinking that no route is secure enough. Address translation is actually a kind of first-class server technology, and not allowing business access to pass through directly is a step forward in security, but at present, the bypass NAT technology at the application layer is very common, and hiding the address is only relative. At present, many attack technologies are aimed at firewalls, especially firewalls have no control over the application layer, which facilitates the entry of Trojans, and the Trojans entering the intranet see the intranet address and directly report to the attackers on the extranet.

1. The three modes of data exchange are: line switching, message switching, and packet switching.

2. The first type: line switching (circuit switching). After the line is established and before the line is released, even if there is no data to be transmitted between the stations, the entire line is still not allowed to be shared by other stations; Once the line is established, all the resources (including line resources) of both sides of the communication are used for this communication, except for a small amount of transmission delay, there is no other delay in the circle, and it has good real-time; Simple line switching equipment; Transparent transmission of user data.

The second type is message exchange. Non-exclusive line, the data of multiple users can be shared by storing and queuing a line; improve the utilization rate of the line; Support multi-point transmission (one packet is transmitted to multiple Yuzhou users, and the "address field" is added to the message celebration and warning, and the intermediate node is copied according to the address field); The intermediate node can convert the data format to facilitate the receiving site's collection; Error detection function is added to avoid unnecessary transmission of erroneous data.

3. The third type: packet switching. It has the advantages of both circuit switching and message switching; After each group is identified, the technology of dynamic multiplexing is adopted on a physical line to transmit multiple data groups at the same time. Packet switching has higher circuit utilization, smaller transmission delay than packet switching, and better interactivity.

Ways of data exchange and advantages and disadvantages:

Storage mode:

1) Advantages: It ensures the error-free transmission of data frames.

2) Disadvantages: The transmission delay is increased, and the transmission delay increases with the length of the data frame.

Quick Mode:

1) Advantages: Low latency of data transmission.

2) Disadvantages: Unable to check and correct the data frame.

Free Segmentation Mode:

The performance of this mode is somewhere between Storage mode and Express mode. In the free fragmentation mode, when the switch receives a data frame, it performs an operation once it detects that the data frame is not a conflicting fragment. Collision fragmentation is the fragmentation of a data frame that has been damaged by a network collision and is characterized by a length of less than 64 bytes.

Collision fragments are not valid data frames and should be discarded. Therefore, the switch's free segmentation mode is actually the first time that the data frame has been received exceeds 64 bytes.

There are them available online.

I can't remember for a while.

1. Line exchange.

The so-called line exchange is the establishment of a dedicated communication line between two stations through the nodes in the network. As shown in Figure 1, this kind of line switching system has an actual physical connection between two stations, and this connection is a connection sequence between nodes. A point-to-point line must be established between the transmission of any data.

If site 1 sends a request to node 2 and requests a connection to site 2, then site 1 to node 1 is a dedicated line. A dedicated channel is assigned on the switch to connect to the communication from node 2 to site 2. So far, a physical communication channel has been established from site 1 through node 2 to site 2.

This allows the voice to be transmitted from Site 1 to Site 2, and generally this connection is full-duplex and can transmit voice (data) in both directions.

Second, the message is handed over to the hail sensitive ruler for replacement.

If a station wants to send a message (a logical unit of information) to site 2, it appends the address (encoding, called the address code) of site 2 to the message to be sent. The packet is then sent from node to node over the network, and the entire message is received in its entirety at each node (e.g., it needs to pass through multiple nodes to be sent to site 2) and the message is staged before being sent to the next node. In a switching network, each node is an electronic or electromechanical switching device, and each node is usually a general-purpose small computer.

It has sufficient storage capacity to cache incoming messages. The delay time of a packet at each node is equal to the time required to receive all bits of the packet, plus the waiting time and the queuing delay time required to retransmit to the next section.

Packet exchange has the following advantages:

1. The line efficiency is high because many packets can share a node-to-node channel in time-sharing mode.

2. There is no need to use the transmitter and receiver at the same time to transmit data, and the network can temporarily store the message before the receiver is available.

4. The message exchange system can send a message to multiple destinations.

5. It can establish the priority of messages.

6. The message exchange network can be converted in speed and quality, because each station can be connected to other points with its unique data transmission rate, so two stations with different transmission rates can also be connected, and the format of the transmitted data can also be converted. Source height.

3. Packet switching.

Packet-switched mode has the advantages of both packet switching and line switching. It is very similar in form to message exchange. The main difference is that the length of the transmitted data unit should be limited in the packet switching network, generally the number of bits of the message data that can be transmitted in the message switching system can be very long, while in the packet switching, the maximum length of the transmitted message is limited, such as beyond a certain length, the message must be divided into fewer units, and then sent in turn, we usually call these fewer data units packets.

This is where message switching differs from packet switching.

Message switching, circuit switching, packet switching.

The data switching technologies are mainly circuit switching, packet switching, and ATM (asynchronous transmission). Circuit switching is a direct communication method that establishes a dedicated communication channel between a pair of stations through switching nodes. Packet switching does not require a physical path to be established beforehand.

As long as the front line is free, it is sent in groups. After receiving the packets, the intermediate node can do so without waiting for all packets to be received. ATM is a transmission mode that combines the advantages of circuit switching and packet switching.

This technology is suitable for high-bandwidth and multi-** transmission, and can be used to transmit voice, data, graphics, and TV signals at high speeds.

A communication subnet is a network formed by the interconnection of several network nodes and links according to a certain topology. These switching nodes in the middle are sometimes referred to as switching devices. These switching devices do not process the data that flows through them, but simply transfer the data from one switching device to another until the data reaches its destination.

A subnet is a path that provides a complete transmission path for all data entering the subnet, and the technology that implements this data path is called "data exchange technology".