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An introduction to Monitoring Fundamentals strictly from the perspective of telecom network alarm management.

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TL1 - The origin of today's widely used protocol

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In the early 70's, network operations began to increase and many companies started using Man-Machine Language (MML), a protocol readable by both humans and machines, to control equipment elements both locally and remotely. In 1984, Bellcore, an equipment manufacturer and research institute for the Regional Bell Operating Companies (RBOCs) and the de facto standards organization throughout the 80's, specified Transaction Language 1 (TL1) as the standard protocol.

Bellcore changed its specification in 1988 to Common Management Interface Protocol (CMIP), another ASCII-based human readable language. However, perhaps because of its perceived complexity, CMIP was never widely implemented and TL1 continues to be the dominant network management protocol.

After divestiture, many new companies began using a variety of protocols within their networks, but TL1 remains arguably the most widely used protocol in North America today.

TL1 is a highly structured management interface that uses a standard command line interface while providing for vendor extensions where appropriate. Messages for fault, configuration, performance, security and testing can all be accommodated by a TL1 interface.

The TL1 protocol is considered a legacy protocol because of its age but is still being used in a variety of new equipment. Mediation of TL1 is increasingly important with different protocols being used in contemporary telemetry monitoring networks.