1. Questions raised
With the development of computer technology, microelectronic technology and communication technology, a variety of networking technologies have emerged, and a variety of network architectures coexist. Although in recent years, the mature open networking technology represented by TP / IP and ETHERNET has shown its unique advantages in scientific research, information processing, etc., but a single network connection method faces the current application of more networking The required high bandwidth rate, high maintainability, and high reliability are still inadequate, especially in terms of network failure protection and network control management.
Therefore, the use of traditional serial communication networking technology, in conjunction with the existing C / S open networking model, low-cost expansion to build a safe and efficient double-layer network platform, has become an attempt to solve the above problems.
2. The basic model of the two-layer network
The so-called double-layer network actually separates "network control information" from "network data information", and forms a double-layer communication channel between control information flow and data information flow between each computer node. Among them, the data flow transmission depends on the currently popular high-speed network architecture with TCP / IP and ETHERNET as representative technologies, and the control information flow mainly depends on the flexible serial networking technology.
Of course, this two-layer network mode is still different from the computer internal data bus and control bus separation mode. The two-layer network is not classified transmission in the absolute sense for the data transmitted between the networks, but the classification transmission in the non-failure state, that is, when a single network connection fails, or a layer of network system is facing the threat of paralysis, the two-layer network The safe operation mechanism of the system will use the remaining network links for backup work and mixed transmission of data to ensure the continuity of network applications.
It should be particularly pointed out that the double-layer network is a double-layer network in the sense of "parallel", and is not a simple connection between an Ethernet device and a serial device. Among them, control information and data information are not absolutely divided. Control information refers more to signals used to manage and control equipment. More control information to ensure communication is still mixed with network data for transmission.
The two-layer network platform has the following characteristics:
· Realize the separation of information flow · Local redundancy of the network · Belong to the physical safety network · A variety of networking technologies coexist
Of course, each layer in the two-layer network platform uses the same networking technology for redundant configuration in the full sense, and its benefits will be reflected in ease of use, but its construction cost and system are widely compatible It will lose some advantages, so it is not the main recommended model for the two-layer network architecture.
On the other hand, instead of using control information and data information offloading technology, only using traditional mature communication protocols, combined with the physical structure of the double-layer network, in view of the existing network needs, it has a wider application prospect in many fields. However, this application method does not deeply explore the transmission advantages of the double-layer network architecture, especially under the normal operation of the network, which is far from the highest efficiency of the network operation.
3. Use the serial port technology to construct the theoretical basis of the control plane
The use of serial communication networking technology to construct the control layer is an important technical feature of the application of the double-layer network platform and a guarantee for the double-layer network platform to demonstrate its application advantages.
1) Serial networking technology is increasingly mature
From RS-232 to RS-422, and then to RS-485, serial communication standards are constantly advancing, with short communication distances and low rates, which no longer become a defect affecting serial communication applications. On the contrary, serial networking technology has solved the problem of multi-point and two-way transmission, and has become an extremely economical communication technology with considerable noise suppression, transmission rate, transmission distance and wide common range.
Because RS-485 serial bus has long distance, high transmission rate and strong anti-interference ability, it is very reliable and stable in the control system.
According to the requirements of the system working environment and system reliability, the transmission parameters can be flexibly adjusted, especially by adjusting the transmission baud rate, a balance can be found between the transmission distance and the transmission rate to achieve higher application requirements.
2) Low cost and high compatibility expansion
The serial port networking technology is used to build the control plane of the double-layer network platform. It does not require large-scale transformation of the existing computer to achieve immediate networking, while immediate networking for other serial devices is easier. Even if there are multiple serial interfaces on the same network, the conversion between them is also very convenient. Especially for those real-time systems, network upgrades can be achieved without interrupting operation.
3) Support for existing serial networking equipment
It is very convenient and fast to build a double-layer network platform using serial port technology, because there are already many mature serial port networking devices to provide support for it. More mature products include embedded serial network access equipment, serial power switch management service equipment, serial network server, network sharer and router equipment. In other words, it is quite mature for serial port networking hardware devices.
4. Operation failure protection of the double-layer network platform.
Failure protection is an important operation mechanism of the double-layer network platform, which mainly solves the problem of network operation failure protection. As we all know, in many application fields, the requirements for the smooth operation of network information are very high. For a single link network, once damaged, even if the backup system can be quickly started, it is impossible to achieve complete transparency in the full sense.
The two-layer network architecture solves this problem very well. Once the TCP / IP-based link is damaged, a network that is more than a serial interface can take over the task of transferring information. Similarly, a link based on TCP / IP can also be used as a backup link for control information transfer. Of course, when the network is operating in a fail-safe state, its transmission capacity will be significantly reduced. At this time, the damaged network can be maintained to use the network for normal operation as soon as possible.
5. There are many application problems
1) Separation and merging of information flow
To build a two-layer network platform, it is especially important to separate and merge data information and control information. In a normal network, the two types of data are separated, while in a non-normal network, the two types of data are combined. Therefore, it is necessary to do some expansive research on the communication protocol, and it is required to enable a specific protocol as a rule of communication guarantee in the failure state.
2) Monitoring settings
The normality of the monitoring network requires that the two layers in the network detect each other. For its implementation, there are two ways of software and hardware. Among them, software monitoring is mainly based on the port status, while hardware monitoring is mainly carried out by checking the data flow. As for the network switching, of course, it should be implemented according to the conclusion of monitoring.
6. Prospect of related technologies
Double-layer network is mainly a solution for some special requirements of network operation. Due to the redundancy of its network architecture, although the network operating costs have been increased to a certain extent, its improvement in network stability is obvious, so it has a very broad application prospect in many fields, especially in industrial automation field.
We mainly discussed the tentative scheme of establishing a double-layer network platform. The actual application of the double-layer network still needs to be improved by the communication protocol and related networking equipment, and the current multiple networking technologies and network architectures in practical applications are more of a network layer technology interconnection. The double-layer network problems discussed here are more based on information flow research, which will be more beneficial to improve network security. In particular, it should be pointed out that the deeper research on data flow and control flow will greatly promote the update and development of network topology.
With the development of computer technology, microelectronic technology and communication technology, a variety of networking technologies have emerged, and a variety of network architectures coexist. Although in recent years, the mature open networking technology represented by TP / IP and ETHERNET has shown its unique advantages in scientific research, information processing, etc., but a single network connection method faces the current application of more networking The required high bandwidth rate, high maintainability, and high reliability are still inadequate, especially in terms of network failure protection and network control management.
Therefore, the use of traditional serial communication networking technology, in conjunction with the existing C / S open networking model, low-cost expansion to build a safe and efficient double-layer network platform, has become an attempt to solve the above problems.
2. The basic model of the two-layer network
The so-called double-layer network actually separates "network control information" from "network data information", and forms a double-layer communication channel between control information flow and data information flow between each computer node. Among them, the data flow transmission depends on the currently popular high-speed network architecture with TCP / IP and ETHERNET as representative technologies, and the control information flow mainly depends on the flexible serial networking technology.
Of course, this two-layer network mode is still different from the computer internal data bus and control bus separation mode. The two-layer network is not classified transmission in the absolute sense for the data transmitted between the networks, but the classification transmission in the non-failure state, that is, when a single network connection fails, or a layer of network system is facing the threat of paralysis, the two-layer network The safe operation mechanism of the system will use the remaining network links for backup work and mixed transmission of data to ensure the continuity of network applications.
It should be particularly pointed out that the double-layer network is a double-layer network in the sense of "parallel", and is not a simple connection between an Ethernet device and a serial device. Among them, control information and data information are not absolutely divided. Control information refers more to signals used to manage and control equipment. More control information to ensure communication is still mixed with network data for transmission.
The two-layer network platform has the following characteristics:
· Realize the separation of information flow · Local redundancy of the network · Belong to the physical safety network · A variety of networking technologies coexist
Of course, each layer in the two-layer network platform uses the same networking technology for redundant configuration in the full sense, and its benefits will be reflected in ease of use, but its construction cost and system are widely compatible It will lose some advantages, so it is not the main recommended model for the two-layer network architecture.
On the other hand, instead of using control information and data information offloading technology, only using traditional mature communication protocols, combined with the physical structure of the double-layer network, in view of the existing network needs, it has a wider application prospect in many fields. However, this application method does not deeply explore the transmission advantages of the double-layer network architecture, especially under the normal operation of the network, which is far from the highest efficiency of the network operation.
3. Use the serial port technology to construct the theoretical basis of the control plane
The use of serial communication networking technology to construct the control layer is an important technical feature of the application of the double-layer network platform and a guarantee for the double-layer network platform to demonstrate its application advantages.
1) Serial networking technology is increasingly mature
From RS-232 to RS-422, and then to RS-485, serial communication standards are constantly advancing, with short communication distances and low rates, which no longer become a defect affecting serial communication applications. On the contrary, serial networking technology has solved the problem of multi-point and two-way transmission, and has become an extremely economical communication technology with considerable noise suppression, transmission rate, transmission distance and wide common range.
Because RS-485 serial bus has long distance, high transmission rate and strong anti-interference ability, it is very reliable and stable in the control system.
According to the requirements of the system working environment and system reliability, the transmission parameters can be flexibly adjusted, especially by adjusting the transmission baud rate, a balance can be found between the transmission distance and the transmission rate to achieve higher application requirements.
2) Low cost and high compatibility expansion
The serial port networking technology is used to build the control plane of the double-layer network platform. It does not require large-scale transformation of the existing computer to achieve immediate networking, while immediate networking for other serial devices is easier. Even if there are multiple serial interfaces on the same network, the conversion between them is also very convenient. Especially for those real-time systems, network upgrades can be achieved without interrupting operation.
3) Support for existing serial networking equipment
It is very convenient and fast to build a double-layer network platform using serial port technology, because there are already many mature serial port networking devices to provide support for it. More mature products include embedded serial network access equipment, serial power switch management service equipment, serial network server, network sharer and router equipment. In other words, it is quite mature for serial port networking hardware devices.
4. Operation failure protection of the double-layer network platform.
Failure protection is an important operation mechanism of the double-layer network platform, which mainly solves the problem of network operation failure protection. As we all know, in many application fields, the requirements for the smooth operation of network information are very high. For a single link network, once damaged, even if the backup system can be quickly started, it is impossible to achieve complete transparency in the full sense.
The two-layer network architecture solves this problem very well. Once the TCP / IP-based link is damaged, a network that is more than a serial interface can take over the task of transferring information. Similarly, a link based on TCP / IP can also be used as a backup link for control information transfer. Of course, when the network is operating in a fail-safe state, its transmission capacity will be significantly reduced. At this time, the damaged network can be maintained to use the network for normal operation as soon as possible.
5. There are many application problems
1) Separation and merging of information flow
To build a two-layer network platform, it is especially important to separate and merge data information and control information. In a normal network, the two types of data are separated, while in a non-normal network, the two types of data are combined. Therefore, it is necessary to do some expansive research on the communication protocol, and it is required to enable a specific protocol as a rule of communication guarantee in the failure state.
2) Monitoring settings
The normality of the monitoring network requires that the two layers in the network detect each other. For its implementation, there are two ways of software and hardware. Among them, software monitoring is mainly based on the port status, while hardware monitoring is mainly carried out by checking the data flow. As for the network switching, of course, it should be implemented according to the conclusion of monitoring.
6. Prospect of related technologies
Double-layer network is mainly a solution for some special requirements of network operation. Due to the redundancy of its network architecture, although the network operating costs have been increased to a certain extent, its improvement in network stability is obvious, so it has a very broad application prospect in many fields, especially in industrial automation field.
We mainly discussed the tentative scheme of establishing a double-layer network platform. The actual application of the double-layer network still needs to be improved by the communication protocol and related networking equipment, and the current multiple networking technologies and network architectures in practical applications are more of a network layer technology interconnection. The double-layer network problems discussed here are more based on information flow research, which will be more beneficial to improve network security. In particular, it should be pointed out that the deeper research on data flow and control flow will greatly promote the update and development of network topology.
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