Despite its age, TL1 is found in a surprising number of networks. This is especially true if you have SONET optical network gear. You can find TL1 used for contact closure monitoring, event monitoring, SCADA, and remote site monitoring.
Sometimes, specific examples are the best way to start learning. These are very specific, but you can likely use similar TL1 implementations in your network:
Monitor AFC equipment via TL1 with T/Mon.
Report to Your Alcatel TSM-8000 with T/Mon Mediation.
What good is a protocol if you don't know the commands you can use? TL1 commands are basic elements of TL1 alarm monitoring. The list below is a reference for some of the most common TL1 commands used in network reliability management.
Because it's ASCII-based, TL1 can be effectively parsed with a text-analyzing master station like T/Mon. With the T/Mon ASCII Processor software module, this master station is about to break down TL1 into its component parts and incorporate it into any modern monitoring system (ex. SNMP, DNP3...).
The TL1 language consists of a set of messages. There are 4 kinds of messages:
Standard Command-line Interface:
TL1 provides an industry standard command line interface CLI. It is useful for managing network elements. It is also flexible enough to allow for vendor extensions where appropriate.
TL1 messages are in plain ASCII text, so staff and developers alike can always read them. As messages are easily readable, TL1 does not require sophisticated debuggers or protocol analyzers - what you see is what you get.
Unlike protocols such as SNMP, TL1 has a well-defined set of management services. These handle performance, fault, security and other areas of management. For instance, an operator has standard ways to do things. He or she can set up performance schedules and receive performance reports from any vendor's TL1-manageable NE.
Tracking of Alarms/Events:
TL1 easily tracks and handles events with a built-in identifier, or "alarm correlation tag" called an ATAG. This unique identifier TL1 is inserted in each autonomous alarm or event message sent from an NE. If an alarm message is "lost," the manager knows about it, as the ATAG of the next event is not in sequence.
Both SNMP and TL1 share the following benefits:
TL1 is a multi-vendor and multi-technology protocol with comprehensive management support. There's a very good chance that TL1 protocol plays a significant role in your network. A solid foundation of TL1 knowledge allows you to do your job more effectively.
TL1 is a set of ASCII-based instructions, or "messages". Because TL1 is text-based, a jumble of code won't intimidate you. This makes the learning curve for basic TL1 much shorter than with other protocols.
However, this doesn't mean that you won't need a basic introduction to TL1 basics. You must learn the basics first. Only then you can read, understand, and write TL1 commands. Fortunately, TL1 message formats are very well defined and documented. You can learn about the most frequently used commands in this guide.
The response message is a reply sent by the NE in response to an input message. The response comes upon the completion of the task requested by the TL1 input message. It states whether or not the requested task was completed successfully.
Autonomous messages, the most frequently used TL1 response type, are output messages sent by the NEs to report alarms. They can also report performance data, configuration changes, or condition changes.
TL1 commands request an action to be executed by the recipient of the message.
An acknowledgment message is a special reply sent by the NE in connection with a delayed command. This special response is issued after the receipt of the command and indicates the status of the request.
High Bandwidth Requirement:
One potentially significant TL1 challenge is the high bandwidth required for transmission of ASCII text. This becomes an issue if you are reporting over slower transports such as dialup or 1200 baud.
Strict Message Formats:
TL1 can also create issues for users because it is very structured. Any deviation in the command message will result in an error. Using an automated TL1 interface for day-to-day tasks will eliminate typing errors and increase your efficiency.
Unlike polled protocols, TL1 sends autonomous messages to your master. While this reduces network traffic, it also means that you do not automatically receive notification that a network element is down. What if you're not receiving autonomous alarms from a device? What will you know? Sadly, you won't know for sure whether the situation is normal or your TL1 device has failed. You must send a command to act as a "ping". If you receive a reply, you will know that your network element is online.
Products Related to TL1 Commands: