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Ethernet Encapsulation

EDW100 Media Converter

What is Ethernet Encapsulation?

Like any great piece of new technology it's important to understand what it is before one can determine how to use it, but before we dig into what Ethernet Encapsulation is let's start with a possible real world scenario.

You arrive at work one day, and are informed that the IT department wants to gather data from each machine on the plant floor. The IT guys, unfamilar with the industrial side of the facility think this will be easy since they dictated that Ethernet cabling be strung through out the plant. Unfortunately all of your existing PLCs only have serial connections.  

In the not too distant past, you would have had to contemplate running new wiring to each PLC, assuming the distances weren't too far. Another option would have been to use costly radio modems. Still, you knew there had to be a better way using the plants existing Ethernet wiring.

That's where media converters (terminal servers) from Westermo come into play. A media converter, such as the EDW100 is essentially a virtual serial port. More importantly, a virtual serial port that can sit on your existing Ethernet network.

The task of connecting all of your controllers just took a big step back into the realm of possibility. You will be able to place a media converter next to each machine gathering operational data directly from the serial ports of the controller, and bring that data back to the IT guys via their Ethernet cabling. Problem solved.

Now that you have an idea of what type of problems can be solved by using a media converter, we can explain what Ethernet Encapsulation is and how Kepware has added this technology to make your job easier. If you are already familiar with media converters, you may also know that many of them supply accompanying software that allows the media converter to appear like a serial port to your operating system. This software can make using a media converter very easy and wouldn't have required Kepware to make any changes to our software, except for one thing - timing.

Many of the devices in the industrial market have very complicated protocols. A protocol is a specification that determines how we talk to the device. In many cases there are also some very tight timing requirements that must be met in order to successfully communicate with the device. Taking these things into consideration, the software that often accompanies media converter devices has not been optimized to work with the requirements of the plant floor environment. This is usually seen as frequent communications errors, continuous breaks in the communications, and long delays while the supplied software reconnects to the media converter. All of these problems can make your use of a media converter less than ideal.

Ethernet Encapsulation:

Ethernet Encapsulation is the enhanced ability of KEPServerEX serial drivers to communicate directly with media converters. As described in the previous section, we could have used the software supplied with the media converter, but this would not have yielded the most optimal result in terms of performance or reliability. With this in mind, Kepware has incorporated the functions needed to directly connect to a serial device connected to an Ethernet based media converter.

If you are familiar with Kepware's serial drivers, you already know you can select a serial port number from 1 to 100 when configuring a channel. For drivers that support Ethernet Encapsulation you will now find that you also have the option of selecting "Ethernet Encapsulation" mode. The following dialog demonstrates how this selection is presented:

Configuring the channel for Ethernet Encapsulation mode is only half of the story. As with any Ethernet based connection you must also specify an IP address, a port number, and the Ethernet communications format to be used. This is done when you add a new device to your channel.

When a new device is added to the channel, the Ethernet Encapsulation settings will allow you to select an Ethernet IP address, an Ethernet Port number, and the Ethernet protocol to be used. The device dialog for Ethernet Encapsulation appears as follows:

This dialog appears on the properties of each device you add to a channel in Ethernet Encapsulated mode. Since this dialog appears for each device, you can have hundreds of serial devices connected to your Ethernet network.

Important Note: When you select Ethernet Encapsulation mode you will notice that the serial port settings such as baud rate, data bits, and parity become greyed out. This occurs because these settings will not be used in Ethernet Encapsulation mode. The media converter must, however, have its serial port properly configured to match the requirements of the serial device you plan to attach to the media converter.

Visit our OPC Download Page to determine if the driver you need supports this feature. Manuals are provided for each OPC Suite. If you have further questions regarding how Ethernet Encapsulation works or how you can use it to solve your next tough communications task, please contact us. If it sounds like Ethernet Encapsulation is your ticket to beating your next connectivity challenge, download our free demo version of KEPServerEX and give it a try.

About the EDW100:

The EDW100 is an industrial Ethernet to serial interface adapter designed for harsh environments. It allows serial devices to interface through a new or existing Ethernet network. The unit can support either RS-232, RS-485 or RS-422 based protocols running at up to 115.2 kbit/s. Ethernet connection is via a standard RJ-45 port with MDI/MDI-X.

Serial/IP® and Telnet Options EDW100 are bundled with Serial/IP® avertual Com port director software. The Serial/IP® use portions of the “Telnet Environment Option” (RFC1572) to verify that it is con-nected to an EDW100.The EDW100 has partial support for the “Telnet Com Port Control Option” (RFC2217). This makes it possible to remotely (on the fly) change serial port parameters. Currently supported parameters are baud rate, parity, number of data bits and number of stop bits.As default the Telnet Options are disabled. If the Serial/IP® software is to be used, the Telnet options must med enabled in the web tool. This parameter can be found on the serial page.

Application Modes:

  • User Datagram Protocol (UDP): UDP provides a connectionless datagram service. This means that the arrival of data-gram’s or data packets is not controlled and the reliability of the communication is the responsibility of the application layer protocol. In this way UDP is a simpler method of communication than TCP. As data is sent and received without any established connection the data transfer is more efficient and often faster. UDP is therefore used in applications that require efficient use of the bandwidth and also have a higher level protocol to handle lost data.
  • Transmission Control Protocol (TCP): TCP is a connection-oriented delivery service. Connection oriented means that a con-nection must be established before hosts can exchange data. An acknowledgement is used to verify that the data was received by the other host. For data segments sent, the receiving host must return an acknowledgement (ACK). If an ACK is not received, the data is retransmitted. Flow-control between the hosts is managed by TCP. For larger amounts of data that have to be split between packets TCP provides a method for reli-ably reassembling the data in the correct order. Because of the requirement to establish a connection and acknowledge transmissions, TCP takes longer time to transmit data than UDP and uses more bandwidth.
  • TCP Server mode: This mode makes it possible to accept incoming TCP connections attempts to the EDW-100 from an TCP client e.g. a EDW100 in TCP client mode. Other examples of TCP clients: Telnet client establishing a raw TCP connection, COM-port redirector software running on a Windows PC.
  • TCP Client mode: This mode makes it possible to establish a TCP connection to a remote TCP server e.g. a EDW-100 in TCP Server mode.DSR signal rising or a powering up the unit will trigger the EDW100 to make an connection attempt to the specified server depending on configuration.
  • UDP mode: UDP is a connection less protocol sending datagram’s i.e. there are less overhead traffic compared to TCP and no acknowledgement packets will be sent between the peer’s during communication.Using UDP will enable the EDW-100 to send and listen to broadcast- and multicast messages
  • ModBus Gateway: Modbus is a communication protocol developed by Modicon systems. The EDW-100 Modbus gateway is used for interconnecting a TCP/IP Modbus network and a serial line Modbus network (either RTU or ASCII). It permits Modbus clients (masters) on either of the TCP/IP or the serial network to connect to Servers (slaves) on the other network. In a standard Modbus network, there is one master and up to 247 Slaves, each with a unique slave address from 1 to 247. The master can also write information to the slaves. The official Modbus specification can be found at Server modeAllows up to 16 Modbus clients (masters) on a TCP/IP network to connect to servers (slaves) on the serial network.

Note: Ethernet Encapsulation mode has been designed and tested using the Digi IA Series by Kepware. The features developed will also work with other media converter devices that support operational characteristics similar to the products listed above. If your media converter supports a raw TCP mode it should work with this feature.

If KepserverEX were only about communications drivers your application objective of connectivity would be accomplished. However, KepserverEX isn't only about drivers, but also deals with other aspects, such as device management. KepserverEX offers an SNMP suite whereby incorporating MIB tags from your Ethernet hardware (Westermo) enables you to monitor your devices through your Ethernet network. Functionality reserved for your IT department is now available to manufacturing:

  • Import MIB files from manageable devices and easily map network device MIB addresses to SNMP tag names.
  • Network Analyst gathers raw SNMP data from network devices and continually performs calculations to generate data that can be used, such as bandwidth utilization and network error rate statistics.
  • Save time by using the Auto-Discovery tool to search your Ethernet network for managed network devices.
  • The SNMP OPC Server provides convenient "Specialty tags" to help users know more than the current value of a single polled OID. The tags include: History tags, Events tags, Table Offsets, and ScanFloor tags.
  • Historical values are generated by the SNMP OPC Server (not the remote Agent/device) when an OID has valid historical modifiers appended to it.
  • The Ping Device Driver is provided for monitoring your network devices via the ICMP protocol (Ping). The Ping driver was designed specifically for use with 32 bit OPC Server products. The Ping driver provides the ability to monitor the Status of a network device, and the time that it takes for the ICMP message to reach its destination and return a response, the RoundTripTime.
  • MIB Support for managed switches and Ping for unmanaged switches.

Further enhancements to your application are available through KepserverEX plug-ins.

Do you have a data base for which you are needing to send information? KepserverEX is your solution for that as well.

Need redundancy? Kepware is your solution for that as well:

This is but one industry example. Challenge ESI to come up with a solution for the industry you work in. A solution is possible, that will garner synergies in any industry.

Note: Foundation of Ethernet Encapsulation information provided by Kepware.


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