When building Ethernet networks, various classes of switching equipment are used. Separately, it is worth highlighting unmanaged switches - simple devices that allow you to quickly and efficiently organize the operation of a small Ethernet network. This article provides a detailed overview of the EKI-2000 series of entry-level unmanaged industrial switches.
Introduction
Ethernet has long been an integral part of any industrial network. This standard, which came from the IT industry, allowed us to move to a qualitatively new level of network organization. Speeds have increased, reliability has increased, and it has become possible to centrally manage the network infrastructure. The creators of data transfer protocols were not long in coming either. Almost all major industrial protocols such as Modbus TCP, EtherNet/IP, IEC 60870-5-104, PROFINET, DNP3, etc. use an identical or approximate OSI model as a basis. Payload data is placed in a frame and transmitted over an Ethernet network. Almost every modern controller, smart sensor or operator panel is equipped with an Ethernet interface for the ability to connect to the network of the same name. This means that, in theory, an industrial network can use standard Ethernet devices that can be found in corporate, office, and even home networks. However, in practice, a large class of devices has long been formed, which is designed to work specifically with networks such as Industrial Ethernet. It includes network devices adapted to work specifically in an industrial environment, providing reliability, low latency levels, and also meeting various industrial standards that a particular industry requires. In this case, the main βcombatβ unit, as a rule, is an industrial Ethernet switch. This is due to the fact that the switch is a device that allows for reliable and, most importantly, fast interaction between the components and nodes of an industrial network.
The switch is the optimal solution for an industrial network
An industrial switch, or switch, is the main device that is used to build an industrial network. Why a switch? After all, there are other network devices, such as a hub (hub, hub) or a router (router, router). It's all about speed and functionality. The fastest device listed is the hub, some time ago this type of device was very popular due to its low price. In fact, a hub is a multiport repeater, it works at the physical level according to the OSI network model and relays the received data to all connected ports.
On the one hand, such a scheme allows for minimal delays in the network, but on the other hand, the load on the network increases, since the broadcast with such an implementation turns out to be broadcast. This often led to a sharp drop in network performance. The router, in turn, is a device that operates at the network level according to the OSI model and has a very rich functionality that allows you to build traffic routes. Such functionality requires higher device performance, as the information packet is parsed starting from the 3rd level header of the OSI model and higher. As a result, delays become longer, since the implementation on routers is mostly software-based, the price is naturally higher, and such functionality is in demand at the network core level.
As a result, it is switches that are most widely used in industrial Ethernet networks, with different levels and functionality. A switch is more intelligent than a hub and faster than a router because it operates at the link layer according to the OSI model. Traffic is clearly distributed and sent immediately to the destination, which eliminates unnecessary load on network equipment, allowing other segments not to process data that is not intended for them. This is achieved by analyzing the source and destination MAC addresses contained in each transmitted data frame. Such switching allows to achieve minimal delays in traffic distribution, while maintaining an acceptable price level.
In its memory, the switch contains a table (CAM-table), which indicates the correspondence between the MAC address of the host and the physical port of the switch, which just reduces the load on the network, since the switch knows exactly which port to forward the data packet to. However, it should be borne in mind that when the switch is turned on or rebooted, it works in learning mode, since the lookup table is empty. In this mode, the data that comes to the switch is sent to all other ports, and the switch analyzes and enters the sender's MAC address into the table. Over time, the traffic is localized as the switch builds a full mapping table of MAC addresses for all ports.
Now many manufacturers of network equipment for industrial networks offer exactly switches as devices for ensuring interaction between network nodes. The portfolio contains switches of various functionality, as a rule, there are unmanaged, managed and L3 level switches. And if L3 switches are used as an alternative to routers at the network core level and only highly specialized issues are associated with their choice, then the choice between a managed and unmanaged switch comes down to the correct definition of the tasks that a network device should solve. Next, let's look at the basic differences between managed and unmanaged switches.
Managed and unmanaged switches
Managed and unmanaged switches are actually two different devices that operate at the L2 layer of the OSI model. An unmanaged switch is designed to automatically evenly distribute the speed and transmitted traffic among all network members. This is the optimal solution for networks with a small number of terminal devices, the advantages include:
- ensuring high throughput of the Ethernet network;
- short response time;
- Ease of Management;
- availability of additional functionality for data flow control.
A managed switch has a higher cost, is used for large networks, and has the ability to fully control the transmitted traffic, speed, and also has additional management capabilities. In fact, this is the optimal solution for network sections where additional functionality is needed for segmentation, redundancy, information protection, etc. Unlike an unmanaged switch, a managed switch must be configured by specifying a number of additional and mandatory settings.
Unmanaged switches are Plug and Play devices that do not require complex configuration and in-depth knowledge. They allow you to quickly organize the exchange between equipment in an Ethernet network without additional settings. These switches allow Ethernet devices (such as PLCs and HMIs) to communicate with each other, providing a connection to the network and passing information to the destination from the sender. They come with a fixed configuration and do not allow any changes to the settings, so there is no need to prioritize frames and do additional configuration.
Unmanaged switches are primarily used to connect peripherals to network spurs or in a small stand-alone network with few components. In industrial environments, it is necessary to use switches adapted to specific needs.
Industrial switches are designed for various industry applications such as electric power, oil and gas, rail and infrastructure, etc. They are specifically designed to operate in extended temperature, vibration and shock environments and contribute to the creation of a cost-effective and reliable secure network.
Advantech Series Switches
Industrial switches Advantech series are entry-level devices and are designed to quickly organize the interaction of devices by creating an Ethernet network. Currently in series more than 25 devices are included, the table below shows the order number interpretation.
At the same time, the switches can be equipped with both RJ-45 ports and optical ports for data transmission over single-mode and multi-mode fiber, the maximum speed can reach 1 Gbps.
Switch Series Functionality
The functionality of unmanaged switches is usually not something extraordinary. However, let's figure out what functions are still in service with Advantech series switches. .
Automatic MDI/MDI-X connection type detection
This feature allows you to connect any type of Ethernet device to the switches without thinking about the type of cable: straight or crossover.
Typically, a "straight through" cable is used to connect the NIC to the L2 network equipment (hub or switch). To connect two identical network devices to each other or, for example, a network adapter to a router, it is prescribed to use a crossover cable. The presence of the MDI / MDI-X function allows you to use any type of cable in conjunction with the switch.
Automatic Network Type Detection (Auto-Negotiation)
This function, following MDI/MDI-X, belongs to Plug and Play and allows you to automatically detect the type of network and the transmission speed provided by the Ethernet standard. In practice, this is especially important, since equipment with different speed characteristics, from 10 Mbps to 1 Gbps, can be used in the existing network. Auto-Negotiation makes life easier for network users. The device itself will βnegotiateβ about the speed with the boundary βEthernet neighborβ.
Broadcast Storm Protection
Broadcast storm protection is also a very useful feature for switches. A broadcast storm is usually caused by "loops" in the local network or by the misbehavior of one of the network participants. In such cases, the network will be filled with a large number of useless frames, which will affect its speed.
The broadcast storm protection feature on the switch automatically filters out broadcast frames. And when broadcast traffic exceeds a certain threshold, the network is still operational, as the switch automatically reserves bandwidth for the transmission of normal frames.
Broadcast Storm Protection Feature on Unmanaged Switches enabled by default. Detailed information about the threshold values ββfor each model must be specified on the official website of the manufacturer.
P-fail relay
Let's start with the fact that most models of the series designed for the input supply voltage range of 12β¦48 VDC. The input is duplicated and has protection against polarity reversal, as well as against overcurrent by means of a self-resetting fuse. There is a voltage comparator at the input, and when voltage is applied to both inputs, the comparator automatically selects a higher value and makes this input the main one. If the voltage fails at one of the inputs or if its level drops below 12 V, the switch automatically switches to the second channel and closes the P-Fail relay. This function allows you to monitor the state of the power supply network of switches and promptly signal abnormal operation.
LED indication
This function allows you to provide an assessment of the status of the switch when it is visually inspected. Each communication port of the series switch has two LEDs for displaying the transfer rate, connection status and possible collision status. There are also LEDs that duplicate P-Fail relays, which simultaneously work when one of the power circuits breaks.
PoE (Power-over-Ethernet)
On a number of unmanaged switches of the series the Power-over-Ethernet function is implemented. It allows you to provide power to remote devices according to the IEEE 802.3af and IEEE 802.3at (PoE +) standard, where a category 5e or higher twisted-pair transmission line is used as the power line. It is recommended to use a nominal value of 53 ... 57 V DC as a power supply for these switches in order to eliminate the voltage drop on the line.
Built-in EMI/ESD protection
Switch Series have a built-in filtering system for protection against electromagnetic interference and static voltage. On the power line, the switch can provide operability with short-term impulse noise with an amplitude of up to 3000 V DC, as well as with electrostatic discharges on RJ-45 ports up to 4000 V.
Constructive
Absolutely all switches of the series have a rugged metal housing with IP30 degree of protection. Structurally series can be made in two versions, this is either a DIN-rail mounting or a 19β rack mounting. All necessary mounting hardware is included. Also, switches that are designed for mounting on a DIN rail can be mounted on a panel, the mount is supplied.
Conclusion
Industrial unmanaged switches are devices adapted to work specifically in an industrial environment. They provide reliable and fast interaction between Ethernet nodes, and do not require additional settings and configuration. At the moment, an unmanaged switch is a simple budget network device that can solve a fairly large number of basic tasks related to organizing exchange over an Ethernet network. No configuration is required, just take the switch out of the box and connect all the necessary connectors.
Advantech Unmanaged Switch Series , belonging to the described class of devices, supports a wide range of important and necessary functions, such as automatic detection of the MDI / MDI-X connection type, automatic network type detection (Auto-Negotiation), broadcast storm protection, PoE, protection against electromagnetic interference and electrostatic discharges, etc. Together, these features make it possible to use to solve basic tasks of organizing interaction between network and end nodes.
Application example
One of Advantech's clients is . In order to enhance data communication capabilities while reducing the associated costs, CNPC chose Advantech's oilfield monitoring and control solution. The data is transmitted via the cellular network from the field to the control center. Routers were installed with switches in cabinets next to the pump rooms, providing network connectivity for field equipment such as cameras, PLCs, RTUs, and other devices.
Literature
1.
2.
3.
The author is an employee of the company
Source: habr.com