Communications News

How MAN avoids LAN island problem

How MAN avoids LAN island problem – municipal area and local area networks

Kevin Tanzillo


Picture a traffic helicopter hovering overhead at rush hour. But instead of just reporting where bottlenecks develop, the people in the helicopter prevent them.

That pretty well describes the role of network analysts Craig Lillemoen and Fred Veck at McDonnell Douglas Helicopter Co. in Mesa, Ariz.

Their job is to make sure traffic keeps flowing through a metropolitan area network at the sprawling facility where the AH-64A Apache military attack helicopter is made, along with other choppers that are far less intimidating.

The Apache, used in last December’s invasion of Panama, is being produced under a contract running into 1993. The facility also makes lighter military helicopters and commercial models, including some with a new design that eliminates the tail rotor.

Located on the eastern edge of the Phoenix metropolitan area, the multi-building site is webbed with a MAN that is primarily 802.3 Ethernet. Syn-Optics Lattisnet is in each building. Fiber links networked buildings and reaches all the way into wiring closets. Twisted pair completes the trip to the desktop.

The wide-ranging network sprouted about four years ago.

“We started with one building and two Ethernets. They were repeated together, then bridged together, then we added a link between two buildings. It has exploded from there,” says Lillemoen.

“Anything out there that could be networked was added. It’s almost impossible to keep up with.”

The setup avoids independent networks in buildings. A previous emphasis on local area networks brought management and “political entity” problems. Now there is essentially one large network, tied by bridges and routers.

Router Interface

A Cisco Systems router interfaces to the McDonnell Douglas corporate network, while a Wellfleet router ties offsite centers, two of them across the street and the third in Culver City, Calif.

Veck maintains the Cisco router, Lillemoen the Wellfleets. Both have been highly reliable. Veck sees the Wellfleet as easier to upgrade, with floppy disks to Cisco’s PROM (programmable read-only memory) chips. Also, Wellfleet is menu-driven while Cisco has UNIX-type commands. But Veck says Cisco is usually first with additional features and functionality.

“the Cisco is our single point of interface to the corporation,” says Lillemoen. “Off the same segment of coax we connect a Wellfleet router. That takes the data from our remote facilities and puts it onto our campus.”

One of those facilities runs heavy CAD/CAM applications, with average files retrieved across the line of 900 kilobytes to a megabyte. The Wellfleet router handles any aggregate speed of a T1.

“I gave these guys 22 channels of a T1 and I have had no response time complaints,” says Lillemoen. “We also have 46 to 50 PCs over there that do interactive work back to our main campus across the same link. We have six terminal servers out there that run the LAT (local area transport) protocol that go back and forth interactively to all the VAXes on campus.”

The Culver City site doesn’t account for much traffic over the network, but will, once a new time management shop floor data collection system begins operation.

McDonnell Douglas Helicopter supervises the network with a SynOptic management system, along with several LAN analyzers and DEC’s terminal server manager and remote bridge management software.

The latter two run as batch programs verifying hourly that all bridges and terminal servers are working. If not, a VAXmail alert is sent.

There is a help desk at the on-site Network Data Center that takes all problem calls, for any system in the facility. Trouble reports are then distributed to data technician.

Hands-On Management

Lillemoen and Veck do some hands-on management, especially when a problem gets out of control, but generally act as high-level network coordinators and try to prevent problems.

“We build the network and say these are the interfaces you can use and this is what we need to have you attach,” says Lillemoen.

“There’s always going to be someone out on a LAN who gets an evaluation unit in, or changes their software parameters, or otherwise crashes the network.

“You can’t be proactive to that kind of event unless you are physically out there telling them don’t do this, don’t do that.

“But then you are controlling. We don’t want to control, we want to assist or advise. We recommend the stay within these standards. If they deviate and start affecting other people, we will disconnect them.”

Lillemoen figures he has enough fiber capacity between buildings to handle network growth for the next five years, even with upgrading to an FDDI ring or Sonet.

But inside the buildings is a different story.

“If you look at the individual Ethernets, you can run into bandwidth problems there,” he says.

“Inside buildings, I am going to have shortages of fiber. Especially if an FDDI, broadband ISDN, or Sonet standard becomes available to the desktop.”

COPYRIGHT 1990 Nelson Publishing

COPYRIGHT 2004 Gale Group