Transaction Language 1 (TL1) is a widely used management protocol in
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
. It is a cross-vendor, cross-technology
man-machine language, and is widely used to manage optical (
SONET
Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diode ...
) and broadband access infrastructure in
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. TL1 is used in the input and output messages that pass between
Operations Support Systems
Operations support systems (OSS), operational support systems in British usage, or Operation System (OpS) in NTT, are computer systems used by telecommunications service providers to manage their networks (e.g., telephone networks). They support ...
(OSSs) and Network Elements (NEs). Operations domains such as surveillance, memory administration, and access and testing define and use TL1 messages to accomplish specific functions between the OS and the NE. TL1 is defined in
Telcordia Technologies
iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
(formerly
Bellcore
iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
) Generic Requirements documen
GR-831-CORE
History
TL1 was developed by
Bellcore
iconectiv is a supplier of network planning and network management services to telecommunications providers. Known as Bellcore after its establishment in the United States in 1983 as part of the break-up of the Bell System, the company's name ...
in 1984 as a standard man-machine language to manage
network element
In computer networks, a network element is a manageable logical entity uniting one or more physical devices. This allows distributed devices to be managed in a unified way using one management system.
According to the Telecommunications Act of 1 ...
s for the
Regional Bell Operating Companies
The Regional Bell Operating Companies (RBOC) are the result of '' United States v. AT&T'', the U.S. Department of Justice antitrust suit against the former American Telephone & Telegraph Company (later known as AT&T Corp.). On January 8, 198 ...
(RBOCs). It is based on Z.300 series man machine language standards. TL1 was designed as a standard protocol readable by machines as well as humans to replace the diverse
ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
based protocols used by different Network Element (NE) vendors. It is extensible to incorporate vendor specific commands.
Telcordia OSSs such as NMA (Network Monitoring and Analysis) used TL1 as the element management (
EMS) protocol. This drove network element vendors to implement TL1 in their devices.
Language overview
TL1 Messages
The TL1 language consists of a set of messages. There are 4 kinds of messages:
# ''Input message'' - This is the command sent by the user or the OSS.
# ''Output/Response message'' - This is reply sent by the NE(Network Element) in response to an input message.
# ''Acknowledgment message'' - This is an acknowledgment of the receipt of a TL1 input message and is sent if the response message will be delayed by more than 2 seconds.
# ''Autonomous message'' - These are asynchronous messages (usually events or alarms) sent by the NE.
TL1 message structure
TL1 messages follow a fixed structure, and all commands must conform to it. However, the commands themselves are extensible and new commands can be added by NE vendors.
These are some of the message components:
* Target identifier (TID) & Source identifier (SID) - TID/SID is a unique name assigned to each NE. TID is used to route the message to an NE, SID is used to identify the source of an autonomous message.
* Access identifier (AID) - AID identifies an entity within an NE.
* Correlation tag (CTAG) & Autonomous correlation tag (ATAG) - CTAG/ATAG are numbers used to correlate messages.
TL1 input message
Example:
Structure:
TL1 output message
Example:
Structure:
TL1 acknowledgment message
Example:
Structure:
TL1 autonomous message
Example:
Structure:
{, border=1 cellspacing=0
, -
, colspan=8 align=center , TL1 autonomous message
, -
, colspan=3 align=center , Auto Header
, colspan=3 align=center , Auto Id
, colspan=1 align=center , Auto block
, colspan=1 align=center , Terminators
, -
, SID, , Date, , Time
, Alarm code, , ATAG, , Verb
,
,
, -
, ''MyNE'', , ''04-08-14'', , ''09:12:04''
, ''A'', , ''101'', , ''REPT EVT SESSION''
,
,
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
GR-833, TL1 Surveillance and Maintenance Messagescontains 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.
External links
TL1 Toolkit, an Open Source Perl module for TL1Telcordia GR-831-CORE - OTGR Section 12.1: Operations Application Messages - Language for Operations Application Messages
Network management