Editing Transaction Language 1 (section)

===TL1 Surveillance and Maintenance Messages===

TL1 also has application messages for NE and transport surveillance functions. The messages and functions cover a wide variety of NE types, user needs, and supplier innovations.

Telcordia 
[http://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-833& GR-833, TL1 Surveillance and Maintenance Messages] contains the generic functions and messages that pertain to the following generic types of NEs:

* Digital Loop Carrier (DLC)
** Central Office Terminal (COT)
** Integrated Digital Loop Carrier (IDLC)
** Remote Digital Terminal (RDT).
* Digital Terminal and Cross-Connect Equipment
** Automated Digital Terminal System (ADTS)
** Digital Cross-Connect System (DCS)
** Hybrid Add/Drop Multiplexer/Digital Cross-Connect System (ADM/DCS)
** Optical Add/Drop Multiplexer (OADM)
** Reconfigurable Optical Add/Drop Multiplexer (ROADM)
** Low Bit-Rate Voice (LBRV) Terminal.
* Digital Multiplexing and Line Terminating Equipment
** Multiplexer (MUX)
** Add/Drop Multiplexer (ADM)
** Line Terminating Equipment (LTE)
** Repeater (REP)
** Automatic Protection Switching (APS) Equipment.
* Digital Switching Systems
** Circuit Switching (CS) System
** Packet Switching (PS) System (including Access Concentrators).
* ISDN Switching Systems
* SONET Transport Systems
* FITL Transport Systems
** Passive Optical Network (PON).
* Metro Ethernet Systems
* Common Channel Signaling (CCS) Systems
** Signal Transfer Point (STP)
** Service Control Point (SCP)
** Service Switching Point (SSP).
* Supervisory Systems (SSs)
* Environment Monitors (EMs)
* Timing Signal Generator (TSG)

An NE address consists of two types of parameters, routing and access. The maintenance functions can be grouped into the following six categories:

* Alarm Surveillance (AS) − Messages of events or conditions (e.g., carrier group alarms, threshold violations).
* Performance Monitoring (PM) − Generated performance data (e.g., number of errored seconds, number of slips).
* Failure Identification (FI) − Mechanisms within the NE to detect and isolate equipment and facility troubles.
* Recovery and Control (RC) − Maintenance purposes. This includes Maintenance State Control, Loopbacks, External Device Control, Initialization, Emergency Reconfiguration, and Process Inhibit and Termination.
* Maintenance Measurement (MM) − to be used for overall assessment of the NE maintenance process.
* Memory Backup (MB) − To/from non-volatile memory within the NE.

GR-833 provides detailed descriptions of commands and responses in the TL1 format.