Product Details

Ethernet Encapsulation - Bringing Legacy Serial Networks to the 21st Century

 
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 real world scenario that you will be facing soon or may have already faced in your facility.

You arrive at the plant one day, check the work order and find that management is implementing something called "eManufacturing" and now the IT department has orders to gather data from each machine on the plant floor, and they want it quick. The IT guys 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 terminal servers like the DR1 from Lantronix come to your rescue. A terminal server is essentially a virtual serial port. More importantly a virtual serial port that can sit on your existing Ethernet network.



After learning of terminal server devices like the DR1, you begin to breath a little easier. The task of connecting all of your controllers just took a big step back into the realm of reality. You will be able to place a terminal server 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 and you're a hero (until tomorrow).

Now that you have an idea of what type of problems can be solved by using a terminal server device we can explain what Ethernet Encapsulation is and how this technology will your job easier. If you are already familiar with terminal servers like the DR1 you may also know that many of them supply accompanying software that allows the terminal server to appear like a serial port to your operating system. This software can make using a terminal server very easy and wouldn't have required any changes to the driver software, except for one VERY IMPORTANT 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. Think of it like languages - you may use a phone to talk (i.e. an RS-232 connection) but both parties need to speak the same language (aka "protocol") to have a conversation. In many cases there are 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 terminal server 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 terminal server. All of these problems can make your use of a terminal server less than ideal.

Ethernet Encapsulation

Ethernet Encapsulation is the enhanced ability of the TOP Server serial drivers to communicate directly with terminal servers like the Lantronix DR1. As described in the previous section, we could have used the software supplied with the terminal server, but this would not have yielded the most optimal result in terms of performance or reliability. With this in mind the TOP Server serial drivers incorporated the functions needed to directly connect to a serial device connected to an Ethernet based terminal server.

If you are familiar with our serial drivers you already know we let you select a serial port number from 1 to 16 when configuring a channel. For drivers that support Ethernet Encapsulation you will now find that in addition to the com port selection of 1 to 16 you will 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 terminal server you are using must however have its serial port properly configured to match the requirements of the serial device you plan to attach to the terminal server.

Note: Ethernet Encapsulation mode has been designed and tested using Lantronix DR1 CoBox products. The features developed will also work with other terminal server devices that support operational characteristics similar to the CoBox products. We currently can best support you when using Lantronix devices.