Transaction Language 1 (TL1) is a widely used management protocol in telecommunications. It is a cross-vendor, cross-technology man-machine language, and is widely used to manage optical (SONET) and broadband access infrastructure in North America. TL1 is used in the input and output messages that pass between Operations Support Systems (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 (formerly Bellcore) Generic Requirements document GR-831-CORE.
TL1 was developed by Bellcore in 1984 as a standard man-machine language to manage network elements for the Regional Bell Operating Companies (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 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.
The TL1 language consists of a set of messages. There are 4 kinds of messages:
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:
|TL1 input message|
|Command code||Staging block||Payload block|
|Verb||modifier1||modifier2||TID||AID||CTAG||General block||Data block|
|MyNE 04-08-14 09:12:04|
|M 101 COMPLD|
|TL1 output message|
|Response Header||Response Id||Response block||Terminators|
|TL1 acknowledgment message|
|MyNE 04-08-14 09:12:04|
|A 101 REPT EVT SESSION|
|TL1 autonomous message|
|Auto Header||Auto Id||Auto block||Terminators|
|MyNE||04-08-14||09:12:04||A||101||REPT EVT SESSION|
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 Messages contains the generic functions and messages that pertain to the following generic types of NEs:
An NE address consists of two types of parameters, routing and access. The maintenance functions can be grouped into the following six categories:
GR-833 provides detailed descriptions of commands and responses in the TL1 format.