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Transaction Language 1 (TL1) is a widely used, "legacy", 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. It is defined in GR-831 by Bellcore (now Telcordia Technologies).

Contents 1 History 2 Language overview 2.1 TL1 Messages 2.2 TL1 message structure 2.2.1 TL1 input message 2.2.2 TL1 output message 2.2.3 TL1 acknowledgment message 2.2.4 TL1 autonomous message 3 External Links

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:

1. Input message - This is the command sent by the user or the OSS.
2. Output/Response message - This is reply sent by the NE in response to an input message.
3. 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.
4. Autonomous message - These are asynchronous messages (usually events or alarms) sent by the NE.

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.

Example:

ENT-USER-SECU:MyNE:sridev:101::password;

Structure:

TL1 input message
Command code			Staging block				Payload block
Verb	modifier1	modifier2	TID	AID	CTAG	General block	Data block
ENT	USER	SECU	MyNE	sridev	101		password

Example:

MyNE 04-08-14 09:12:04

M 101 COMPLD

"UID=sridev:CID=CRAFT,UAP=1:"

;

Structure:

TL1 output message
Response Header			Response Id			Response block	Terminators
SID	Date	Time	M	CTAG	Completion code
MyNE	04-08-14	09:12:04	M	101	COMPLD	"UID=sridev:CID=CRAFT,UAP=1:"	;

Example:

OK 101

>

Structure:

TL1 acknowledgment message
Acknowledgment code	CTAG	Terminator
OK	101	>

Example:

MyNE 04-08-14 09:12:04

A 1 REPT EVT SESSION

"root:NO,"

;

Structure:

TL1 autonomous message
Auto Header			Auto Id			Auto block	Terminators
SID	Date	Time	Alarm code	ATAG	Verb
MyNE	04-08-14	09:12:04	A	101	REPT EVT SESSION

• Beginner's guide to TL1