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Example: High-Speed Data Services over HFC

To illustrate the management approach, an example of high-speed data services over a HFC network is illustrated in Exhibit 4. The data service is very similar to a standard network service found in many corporations, where PCs have access to each other and a main server complex.

In this example, the real difference is in the network medium and the signal conversion system (which converts Ethernet traffic into RF packets). Instead of 10-BaseT, FDDI or a T1 line, the distribution network is HFC.

In the traditional data network, there would be routers, bridges, and hubs to segment the traffic over the network. These devices have some monitoring capability to indicate the traffic going through them and the number of packets that were resent.

These devices also are part of the management system and have their own management application that can control the type and amount of traffic flowing through them. Typically, this is through the use of MIB and SNMP. Thus, when a problem occurs with a device, it can be used to troubleshoot the data network problems.

HFC Equipment

In the HFC environment, the network uses fiber transmitters, fiber nodes, RF amplifiers and taps to distribute the signals to the subscribers and set-top boxes, or cable modems, to return the signals to the head end.


Exhibit 4.  HFC Network with High Speed Data Service.

No similar management strategy currently exists for the HFC environment. Most HFC equipment currently does not have monitoring capability built in.

Status Monitoring Systems

Many of the HFC devices support an external transponder, or telemetry equipment, that is managed by a status monitoring system. The communication between the status monitoring system and the transponders is through a proprietary protocol. The communication path is through the HFC network to the transponders and through the return path, or telephone line, for the return communication.

The status monitoring system plays an important role in establishing similar capabilities for the HFC network. In the example shown in Exhibit 4, transponders could be placed in the fiber node, trunk or bridge amplifiers, and line extenders. With these transponders, the status monitoring system would be able to indicate the status of those devices in near real time.


Exhibit 5.  Status Monitoring System Represented in Network Management System.

The types of parameters the transponders can measure include AGC levels for the amplifiers, RF levels of various carriers, temperature inside the amplifier or node housing, and laser power level. These parameters allow the monitoring system to predict the current health of the HFC network.

Some specialized monitoring modules, called end-of-line monitors, can perform more detailed measurements on the RF carriers. These parameters are tuned more for analog video (i.e., carrier/noise ratio, depth of modulation, carrier level variation over time) than they are for digital services, but still can be used as a diagnostic tool when problems in digital services occur.

Exhibit 5 shows an example of bringing the status monitoring information into a standard network management system, such as HPOV platform. This example shows a fiber node and the associated RF devices to service a 500-home area. Color is used to indicate the status of the managed objects — red for critical, yellow for major or minor, green for normal, and blue for unmanaged.

Note that although the status monitoring system typically has a proprietary protocol to communicate with the transponders (shown as managed objects in Exhibit 5), they can still be represented in a standard management environment, either through proxy agents or through a mediation device (discussed in more detail later).


Exhibit 6.  Fault Management Platform.

Standard Management Capabilities

Most of the components used for the high-speed data service currently support standard management capabilities. The server complex and ATM switches typically have SNMP capabilities. Home PCs can support some sort of a SNMP agent, allowing them to also be managed as part of the service.

The signal conversion systems and cable modems are relatively new and may not support SNMP capability for the first revisions. Thus, the high-speed digital service could be managed similar to a corporate application, with management products like Hewlett-Packard’s Network Node Manager or Operations Center.


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