Cover Story

ATM and VLAN Management Will Require Strategy Shift

During the next five years, ATM, virtual LANs (VLANs) and managing bandwidth will become the primary management concerns. Each will present certain challenges for network managers, and we fear that the major network management system vendors may leave the support of each of these to third parties. Worse yet, hardware vendors might make it difficult for network management system vendors to support features like reconfiguring VLANs and managing ATM bandwidth.

What's Special About ATM? ATM's connection-oriented nature demands a different type of management. No longer is it a concern that one station will dominate a shared wire, because the wires aren't shared. We hope it will also be less likely that a switch going haywire will cause major network disruptions. Today, routers and hubs are the object of most management efforts, because they are likely points of critical failure. End stations are less of a concern--unless they are critical servers.

In an ATM network, managing the switches may not be any more important than managing the end stations. It is the end station that negotiates for bandwidth all the way through to the station at the other end. Therefore, the end station can report problems with bandwidth allocation to the network manager.

Managing the network will involve managing all the way back to the workstation. When the end station reports problems, it is time for the network manager to start troubleshooting. Most network management stations aren't oriented toward that sort of management.

VLANs--Just Where Is That Station? VLANs present a different problem. The normal method of discovery these days is to find the subnets that make up a network and then ping all possible addresses. This provides a physical view of the network since each subnet is associated with a single router port.

In the VLAN world, you'll end up with a logical view of the network since the idea of VLAN is that devices on the same logical LAN need not be physically near each other. As a network manager, the logical view will be useful, but the real benefit will be from a physical view. The only way to develop a physical view will be to query the switches throughout the network and determine which stations are physically connected to each of their ports.

Sounds like a good place for a standard!

Trunks that connect VLANs must be identified to the management station by the switch. To a contemporary management station, the trunk line will appear to be made up of many lines (the virtual circuits). On a network diagram, most switches would appear to be on most networks and connected to each switch on the network--a rather complex diagram. Ideally, we just want to click on a trunk line and find out which virtual circuits are taking bandwidth. There is no good way to do that and certainly no standard way.

Managing Bandwidth Part of the reason that we're going to the trouble of switching to ATM and setting up VLANs is to support applications that demand constant, reliable bandwidth. We've all seen the commercials that show huge control centers dedicated to managing the telco network. There's good reason for that: Voice traffic is sensitive to bandwidth availability.

It looks like our networks will be expected to support applications like videoconferencing and distance learning, among others. These require reliable bandwidth. We need to demand quality network management products that can help us support the applications that our users--our customers--are going to demand.

October 15, 1995