The process of managing the cable plant

Network management in premises networks started as an expensive add-on to high-end systems, but it has now permeated almost every aspect of the network. It provides at least two primary benefits: the ability to view the status of the entire network, including local and remote elements, from one location as well as access to the information necessary to deal with problems and challenges proactively.

Simple Network Management Protocol (SNMP) is the basis of the most common management approach in premises networks. It has been standardized by the Internet Engineering Steering Group of the Internet Engineering Task Force for network-management applications. An SNMP-managed network consists of several managed items, including media converters, hubs, switches, routers, and servers, which contain hardware and software called SNMP agents. These agents are connected to a common management station that runs management software such as Hewlett-Packard's Open View or another vendor-specific application. The stations gather the information from managed items and display it either graphically or in text format. They also provide a means to configure and control items that are SNMP-compatible.

Network management requires information to be passed from the SNMP agent to the management station and vice versa. Because each managed item is unique, there needs to be a standard way to define it so that any SNMP management system can "talk" to it. This task is accomplished by using a Management Information Base (MIB), which defines status and control items available in a particular piece of equipment and does it in a very structured method. As an example, an MIB might define a media converter as having a status item called "FiberLink" or "CopperLink." With these links, any SNMP software would know that this status information is available and would understand how to obtain it from the media converter.

The exchange of managed information can happen in one of two ways, in-band and out-of-band. Most managed items support both types of connections. The in-band method can be done using SNMP (as described above), telnet, or recently with HTTP (Web-browser-based management). Out-of-band management typically uses an RS-232 port and a dumb-terminal type of interface.

Typically, the SNMP agent only responds to queries from the management system, which is similar to the old parent's adage for children, "Speak only when spoken to." But to allow the system to provide proactive management capabilities, the SNMP agent needs a way to send time-sensitive information without being asked. This capability is accomplished with what SNMP calls "traps." Traps, when received by the management system, can trigger a number of actions such as paging the administrator when there is a problem.

While SNMP management has been used in high-end local-area-network (LAN) equipment for several years, the physical plant has been largely neglected, primarily due to cost issues. Until recently, it was expensive to install equipment that would manage the cable plant. As managers began to deploy fiber, they often used media converters to connect their new plant to legacy copper equipment. These devices were typically not managed and further complicated the issue of managing the physical plant.

Now several manufacturers of media-conversion products offer managed conversion solutions. These are typically in the form of a chassis that can manage 16 or more media converters, allowing the converters to be placed in critical locations within the network.

Networks today are vital to the operation of a company, with the number one objective to keep network downtime to a minimum. Managing the network often requires that all network devices have an SNMP agent to monitor all connections in the cable plant. If all connections are monitored, you can identify a failure at the management station, rather than by visiting wiring closets that could be miles away.

In managed media-conversion systems, port status is the primary piece of information gathered. Simply put: Is the link up or down? This information is available upon request (as when looking at a graphical representation of the product) or as a trap. Traps are sent to the management system as soon as the SNMP agent detects that the link is down. When the link is restored, another trap can be sent notifying the administrator that the problem has been solved.

Some systems monitor environmental data in the wiring closet as well. Information such as temperature and voltage levels are monitored and compared against defined values. If a defined threshold is exceeded, a trap can be sent to the management system.

Additionally, SNMP agents often contain elements that can be controlled. For example, managers could send a command to a port to enable or disable it. Other port parameters such as speed of operation, auto-negotiation, and security controls are often implemented in devices such as fiber hubs and switches.

So how does all of this help the network manager to run the network better? Imagine a network manager working in the telecommunications closet inadvertently rips out a patch cord going to a managed media converter. The media converter senses that the link has been lost and sends a trap to the network-management system. Now, even though the problem could not be prevented, the network manager is able to fix the problem before anyone realizes that the network is down. Without management, the first indication of a problem is when someone calls the help desk complaining about not being able to log onto the server.

Another significant advantage of having SNMP-managed equipment in the fiber cable plant is the ability to monitor and configure ports remotely. Most managed devices support a telnet connection that allows the user to monitor all of the managed data from any computer connected to the Internet. This connection is password-protected for security reasons. By using this telnet connection, the network manager could diagnose network problems from any location. Once the problem is determined, the manager could guide someone on-site through the appropriate steps to fix the problem.

All of these features combine to result in less downtime for the network and better productivity for the company. From a physical-plant aspect, most of these services are available when fiber is deployed, using media-conversion technology to either connect legacy copper equipment or provide a cost-effective solution in a mixed-media infrastructure.

Steve Stange is senior product manager for Minneapolis-based Transition and chair of the Fiber Optics LAN Section of the Telecommunications Industry Association. He can be reached via e-mail at [email protected].