01 April 2002
SNMP puts the brakes on driving with 'blind faith'
By Ellen Fussell
Networking protocol breathes life into Jaguar's 3-D robots
Jaguar is one manufacturer taking advantage of a seasoned networking protocol, but with newfound applications. The company is using simple network management protocol (SNMP), traditionally used in an office setting, in its industrial Ethernet network to run a three-dimensional robot configuration in its automobile production plant in Liverpool, England.
Simple network management protocol (SNMP) is a protocol designed to give remote management access to an Ethernet network device. The protocol started in the 1980s as a tool to allow network managers to monitor and control their rapidly growing TCP/IP Ethernet infrastructures, according to The Online Industrial Ethernet Book. Prior to this, a network administrator would physically attach himself to a network device to access configuration and troubleshooting information.
Although there were initially a number of remote management protocols, SNMP has become the de facto standard. Manageable network devices are actually quite similar to PLCs, in a fashion. An SNMP agent embedded on a microprocessor built into the network device monitors diagnostic and device configuration data. The agent has data stored in memory locations that can be accessed by polling the agent from a remote computer using SNMP.
Controlling processes and building efficiency is what SNMP is all about. While SNMP itself hasn't seen dramatic changes in its 15+ years as an office enterprise protocol, its relevance to the industrial user has become much more apparent. "Traditionally, people in the industry thought they could install their networking, and that's the end," Taylor said. "They hadn't yet realized they needed to monitor their systems. They thought with any luck they'd see changes in behavior before they became serious."
Other SNMP applications could take shape in refineries or factories that need to monitor their processes-the status of tanks, pressure, valves (open or closed), and levels in tanks.
Today, because so many different buses are relying on Ethernet as an infrastructure, the importance of having a healthy Ethernet infrastructure is becoming more critical. And as the realization builds that Ethernet can benefit industrial networks, SNMP's popularity increases. "Industry is getting squeezed to make better products in less time," Taylor said. "Since the goal is to improve processes, the more information manufacturers have available to them, the more efficient they can be."
"Before SNMP, most Ethernet networks just operated on blind faith," said Steve Woram, founder of Dallas-based Industrial Networking Solutions. "With SNMP, you can monitor and record the performance of the entire Ethernet infrastructure, so when a problem occurs, it will give you an alarm," he said. Common uses for SNMP are not just the hubs and switches but the uninterruptible power supplies (UPSs), PCs, printers, and routers. "You name it-it's all manageable," Woram said.
Woram likened the advantages of SNMP to driving a car with a dashboard as opposed to without one. "Both cars would drive, but the one with the dashboard would be easier to control because it would tell you how much gas you had or if the engine is getting too hot," he said. "In the car without the dashboard, you could still drive, but you wouldn't know you had a problem until there was a failure. SNMP is a dashboard on your network that allows you to monitor the performance of the network and react accordingly."
While proprietary buses have their own protocols-Foundation fieldbus, EtherNet/IP, and Profinet-Woram said the more Ethernet protocols out there, the more people will use an Ethernet infrastructure. And as the infrastructure grows, the need to manage it becomes more important, he said.
With an Ethernet switch, if cabling in the network is faulty, it might not make the system fail, but it might make it run poorly. "If the cable were damaged or handling a lot of interference, there would be corruption of the data," Woram said. The SNMP manageable switch will maintain status about how much of the traffic it sees is corrupted data. "If you didn't have SNMP, you would only see the symptom: slow overall performance," he said. "With SNMP, you would see, at a specific port, a large number of bad data packets. And you would know to investigate that port."
Monitoring UPSs in real time is another example of SNMP's benefits. "If there were a power failure-a UPS went from line power to battery power-the UPS would immediately notify you there was a power outage. It would tell you how many minutes you had in real time before the battery went out. It could tell you what type of failure you had," Woram said.
New applications for SNMP
In addition to burgeoning upon a new persona in industrial Ethernet, at Hirschmann, SNMP links information from the network to the SCADA software packages to control the network. "We use OPC to convert SNMP traps [alarms] and alerts into OPC tags, which can be read by the SCADA software," Taylor said.
Jaguar is using Hirschmann's new software, HiVision, for SNMP to link into its SCADA system. "They are monitoring their production line of robots, which are transferring information between themselves: where they are and where their next movement will be," Taylor said. "They'll get out of a certain space if they sense another robot is going to be there."
While SNMP is about monitoring and preventing downtime in your network, the flip side of that is how you can reduce the amount of time the network is down when it does break. Hirschmann's products give recovery times, Taylor said. A process called spanning tree configures a network to become redundant (the ability of the network to heal itself).
"If your network is up and you lose one of the parts being used for data transfer, it could take 30 seconds for the network to reconfigure itself," Taylor said. "In office environments that's OK. But in a manufacturing scenario, 30 seconds is an eternity. If you're drilling an engine block and you have to issue a command to stop, and the command arrives 30 seconds late, you could drill through the floor. You're looking to reduce the amount of time your network, having suffered a fault, takes to recover from that fault."
Spanning tree is something that Hirschmann does, Taylor said, but other players in the industry-Siemens, Rockwell, Mitsubishi, and Schneider-noticed its importance.
At Industrial Networking Solutions, the SNMP product is a tool that allows the human-machine interface (HMI) to interface to the control network and also act as a monitoring system to the Ethernet infrastructure, to monitor the health of the Ethernet network in real time. Woram said his company's SNMP protocol integrates network management data into the existing HMI instead of using a separate stand-alone network management package, allowing users to monitor their network as well as their processes with their HMI software.
Another emerging technology from Industrial Networking Solutions is Industrial SNMP Agent, which will allow any OLE for process control (OPC) server to become a network management agent, Woram said. An SNMP management software package would be able to see any device that communicates OPC. WBJ