LXI, or LAN eXtensions for Instrumentation, standardizes and extends the LAN interface in high-performance test system designs. Using standard Ethernet technology, LXI allows designers to quickly and easily connect to instruments wherever they may be—in the lab, in the plant, or around the world.
LXI systems offer the size and integration advantages of modular instruments without the constraints and cost of card-cage architectures. For example, LXI modules often have no front panel or display. To set up the instrument and read results, a host PC communicates with the instrument via an Ethernet connection. LXI modules also feature self-contained power supplies to improve reliability, lower costs, and enable widely distributed system architectures.
As a test engineer, you probably are well aware of the advantages of using an LXI-based test system and excited about its possibilities. Your company’s information technology (IT) department may not share your enthusiasm. Because these people are responsible for all of the equipment that connects to your company’s network, getting them involved in your project planning early can get you off to a great start.
Your IT department is the guru of routers and cabling but will know little about oscilloscopes or switching systems with an LXI interface. Even so, they can help ensure that LAN instrument connectivity goes smoothly. With a little advance planning, some training, and a cooperative attitude, you can help ensure that your IT department will feel comfortable with your plans.
What Does IT Do?
A modern IT department in a larger business may consist of a manager and a number of technicians. It is the IT manager’s job to handle purchasing and support and ensure the IT equipment works as intended. Part of the job also may include planning for the introduction of equipment.
The IT manager’s job covers a wide range of responsibilities. Essential business systems such as email and accounting all may be handled through this department. Other responsibilities include routine maintenance, disaster recovery, and network security. To ensure that the network runs smoothly and securely, he must make sure that any new hardware connected to the network does not disrupt it. This includes LXI instruments.
What Can Happen?
What can happen if you don’t get the IT department involved early in the design process? Well, at one company, the network was configured to automatically assign IP addresses when new hardware was added to the network. The network, however, was set up to block HTTP information to devices not specifically approved by the IT department.
So when the test engineer connected his LXI instrument to the net, he could not open the instrument’s web page. He was delayed until he could contact the IT department, explain the situation, and get them to add his instrument to the list of allowable devices.
Adding LXI Devices to the Network
To avoid these kinds of conflicts when connecting LXI instruments to your company’s network, you really need to get your IT department involved early. Because you can’t expect the IT department to be test equipment experts, chances are they are not familiar with the capabilities and requirements of LXI. Approaching the IT department early and providing them with basic information about LXI will allow them to plan ahead and make sure your deployment goes smoothly.
One of the first things they will want to know is how many test instruments you plan to connect to the corporate LAN. At this point, you should consider whether the instruments even need be connected to the LAN. If you do not need access to an instrument from the corporate LAN, just isolate it with a router. It will be available to a test lab or production cell network and not on the corporate network. The IT staff doesn’t manage these devices so won’t perceive this device to be a threat to the network.
For instruments that require broader access, providing information about the types and the number of test instruments is necessary so the IT department can plan IP address allocations and supply switches to isolate the local (instrument) traffic from network traffic. IP addresses are to a network what your street address is to the post office. Just as the street address tells the post office where to deliver your mail, an IP address tells the network where to deliver messages over the network.
Every device connected to a network requires its own IP address for messages to be routed correctly. Even if your equipment is isolated from the wider LAN to a cell or lab, IP addresses still are required.
IP addresses may be assigned dynamically or statically. If the network assigns IP addresses dynamically, then your test instrument may have a different IP address every time it is turned on or rebooted. If your network uses static IP addresses, your instrument will have the same IP address all the time. In either case, you will want to determine the IT team’s policy and then configure your instrument accordingly.
Keeping Things Secure
Network security is a key responsibility of the IT department. The data that flows across a network has commercial value, so it must be secured from unauthorized access.
A network connected to the Internet is exposed to a wide variety of threats. Outsiders can hack into the network from the outside to access this sensitive data, but equally damaging threats can come from within the network. Every device, including a test instrument, is a potential security threat. Because of this, the IT department provides firewalls to block most threats and carefully controls the deployment of equipment to minimize these threats. It also may require specific virus protection software for any MSWindows or Linux-based instruments. Your IT department can be your best ally to ensure you are protected from any virus or malware infection.
Figure 1. Diagram of IT Department Responsibilities
One way to minimize the security risk to a corporate network is to set up an isolated subnet for your test system as shown in Figure 1. In this configuration, only the system controller connects to the corporate network.
Most of today’s LXI test systems use this type of network configuration. It not only makes the corporate network more secure, but also puts less load on the network.
Another responsibility of your IT department is network resource allocation. Many people think that setting up a network is simply a job of connecting the LAN ports on their computers to a hub or switch and turning everything on. If your network consists of a few PCs and a workgroup server, this is perfectly acceptable. Larger networks, however, may include hundreds of computers, and simply connecting them altogether with no regard to network topology could create severe problems.
Different types of network connections have different capacities or bandwidths, and an IT manager must have an idea of how information will flow through a network so that he or she can design the network topology. With this knowledge, the IT manager will use higher bandwidth connections such as fiber-optic cable for where they are needed while slower connections will be used for devices such as printers.
Additionally, an IT manager can deploy routers and switches to segregate network traffic to prevent information from one part of a network from being sent to all others. Using routers and switches in this way not only improves network speed, but also network security by preventing access to a part of the network when that access is not required. In most cases, your test instruments will be put on a switch to isolate the test traffic from the rest of the corporate network traffic (Figure 2).
Figure 2. Test System Run as a Subnet to Lessen Threat to Network
For example, an IT manager may configure a router to prevent email from being sent via any other means than the corporate email server. By restricting network traffic to those services which are authorized, more bandwidth is made available to the applications the IT manager actually does want to run, and access is disabled to those which could cause harm.
So, how does LXI affect network design and operation? When you connect LXI test instruments to your company’s network—especially when connecting your device to the corporate network and not just a plant network—you will need to inform your IT manager of the type and volume of data you expect to transfer. Doing so will help ensure that capacity is available and that you will be able to access this data from the appropriate parts of the corporate network.
For example, your quality control department may have to access data from production test stations and then archive the data. The test data obviously is being generated on the manufacturing floor, but analysis and archiving may be taking place on computers connected to the corporate network.
The server on which the data is being archived may be physically distant from the test location. If this is the case, test data may be delayed when it is transmitted from the test cell to the test data server. If the network was not designed properly, these delays could cause production to run more slowly than necessary, resulting in lost production and lost revenue.
The number of services that an LXI instrument provides also is important when connecting one to a network so that the network can provide adequate bandwidth and security.
LXI instruments typically offer very few services. These include a web server used to configure the device and a VXI-11 service for discovery, but this does not mean that an LXI device will provide only these services.
A sophisticated test instrument like a spectrum analyzer will likely provide other services, such as a data transfer service, an instrument control service, and a remote administration service. Other services designed to ease instrument control and datalogging, such as Simple Object Access Protocol (SOAP) and Simple Network Management Protocol (SNMP), also may be available.
The manufacturer determines which services the LXI instrument offers. Some of these services may be controlled via the LXI device’s web interface, giving you the ability to switch off unwanted functionality and reduce the bandwidth requirements of the instrument.
This being the case, you should consider which services are essential before connecting an LXI instrument to the network. For example, SNMP sometimes is used by IT departments for remote administration. They may have to take into account that an LXI instrument has an SNMP service when configuring that part of the network.
Network management is not a simple task. Working with your IT department early on—before connecting that instrument to the network—can help ensure a successful project. Your IT department has the knowledge and experience to help your LXI system deployment go smoothly.
About the Author
Simon Appleby is a member of the Technical Committee for the LXI Consortium and the strategic engineering manager at Pickering Interfaces. He has worked for 12 years in research and development, responsible primarily for the implementation of new technologies. Previously, Mr. Appleby worked as a consultant at positions in both the defense and civilian sectors.
About LXI and the LXI Consortium
The LXI Standard creates new capabilities that optimize test throughput, overall system performance, and cost efficiency in a way that allows engineers to build powerful, web-enabled test systems in less time. The LXI Consortium, a not-for-profit corporation composed of leading test and measurement companies, manages the standard. The group’s goals are to develop, support, and promote the LXI Standard. LXI’s flexible packaging, high-speed I/O, and standardized use of LAN connectivity address a broad range of commercial, industrial, aerospace, and military applications.
Additional information about LXI-compliant products as well as licensing, specifications, and consortium membership is available at www.lxistandard.org.