Designing to maximize network monitoring features
Given the success of the DOCSIS 1.0 specification, aggressive global deployment of these new networks is well underway. Forecasts suggest as many as 5.3 million cable modems will be deployed internationally by 2003 [1], ushering in a new age of high-speed residential Internet access.
However, fortune found in the success of rapid network growth brings with it significant engineering and operational challenges. Large-scale residential Internet Service Providers (ISPs) have often found themselves overwhelmed by the popularity of the access they offer. Oversubscribed resources invite opportunity for poor system performance and network faults. This results in decreased customer satisfaction and a decline in service popularity.
In order to maximize performance and availability, operators of these large-scale systems rely on facilities designed to monitor various resources critical for service availability. These monitors constantly survey the network measuring parameters that provide an interface for operators to detect, isolate, diagnose and remedy problems. With these monitors in place, an operator can proactively maximize service availability, reduce truck rolls and ultimately heighten subscriber satisfaction.
The cable industry faces significant challenges in the area of proactive network management to support the deployment of reliable large-scale DOCSIS (Data-Over-Cable Service Interface Specification) systems. It has been suggested that network reliability and performance are among the most important open technical issues facing the industry today [2]. Clearly, sophisticated systems must be in place to furnish the Service Level Agreements (SLAs) and QoS expectations of users subscribing to these ever-expanding data-over-cable networks.
DOCSIS network monitoring consists of mechanisms indicating the overall "health" of the system as a sum of its elements-both the cable modem termination system (CMTS) and cable modems (CMs). This article explores the standard management features included as part of the current DOCSIS 1.0 design that support an approach to network monitoring.
DOCSIS OSSI and the IETF
Before beginning an exploration of DOCSIS network monitoring, it is useful to understand the work done by standards bodies responsible for developing this technology. The two groups supporting the evolution of DOCSIS network management related standards are the DOCSIS effort (centered at CableLabs [17]) and the Internet Engineering Task Force (IETF).
The DOCSIS OSSI (Operations Support System Interface) [3] is a subset of the overall DOCSIS standard that addresses many areas of network element management, including fault and performance monitoring. By specifying minimum requirements for management functionality in both the CM and CMTS, a consistent interface for remote control and observation of all devices in large-scale, vendor-heterogeneous DOCSIS networks can be realized. This notion of management interoperability using an open standard will enable cable operators and vendors to build monitoring infrastructures based on the assumption that all devices in a multi-vendor DOCSIS network will respond in an operationally consistent manner.
The Internet Engineering Task Force (IETF) also plays a large role in DOCSIS network management both through the development of the SNMP (Simple Network Management Protocol) and within a working group dedicated to the evolution of IP over Cable Data Networks (IPCDN [4]). …
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