1) What is TL1? Transaction Language 1 (TL1) is an ASCII or man-machine management protocol defined by Bellcore. It is used to manage most of the optical, broadband, and access equipment in North America.
2) Does TL1 support multi-vendor management? A protocol is like a truck. It transports information from one point to another. The information conveyed is a matter of choice. Unless the information being exchanged is understood by both systems, no protocol can deliver interoperability. You can use TL1 for the exchange of agreed-upon information as easily as other management protocols like CMIP or SNMP. With OSMINE, Bellcore has a well established process for ensuring that network elements with TL1 support interoperate with its TL1 managers/OSSs like NMA and OPS/INE. No such open process exists for any other management protocol.
3) Why use TL1 ? TL1 is a highly structured management interface that offers many advantages over alternate approaches - simplicity and ease of implementation and use are highest among these.
- Standard Command-line Interface - TL1 provides an industry standard command line interface for managing network elements. It is also flexible enough to allow for vendor extensions where appropriate.
- Human-to-machine Language - TL1 messages are in plain ASCII text, so operators 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.
- Machine-to-machine Language - A TL1 message dialogue can easily provide a communications stream equivalent to a binary encoded stream. Unlike the binary encoded stream however, humans are also able to read the messages. This provides a unique fall back that no other protocol provides - the human operator.
- Small Footprint - Unlike alternative approaches, TL1 has a small footprint that allows it to co-reside with other management protocols and makes it easy to embed on both new and existing network equipment.
- Services - Unlike SNMP for instance, TL1 has a well-defined set of management services for performance, fault, security, and other areas of management. For instance, an operator has standard ways to set up performance schedules and receive performance reports from any vendor's TL1-manageable NE.
4) What services are built into a TL1 interface? There are standard TL1 messages for Fault, Configuration, Performance, Security and Testing. Off-the-shelf OSSs like Bellcore's OPS/INE and NMA leverage these services to manage NEs of many technologies and from different vendors. Management based on services is more powerful than the simplistic "get-set" mechanisms supported in SNMP.
5) Is TL1 suitable for managing today's sophisticated equipment ? There are three basic requirements for a telecom management interface. With the pace of technology improvements, you must be able to develop new interfaces quickly. In addition, as new features are added to an existing element, you must be able to upgrade the management interface easily. Finally, the deployed interface must be able to keep up with the performance and usability requirements of the management systems and network elements that it connects. Because TL1 interfaces are string-based and human-readable, they can be rapidly developed and easily updated. No special decoders are needed for debugging, and new messages can be added with minimal effort. This contrasts with the complex environments required to develop and maintain other protocol interfaces, for which development cycles of 9 to 12 months regularly fall behind hardware enhancements. Finally, TL1 is scalable, as shown by its ability to work with scalable management systems such as Bellcore's Network Monitoring and Analysis system.
6) Is TL1 still being deployed today? Yes, and more widely than ever before. New technologies such as WDM and xDSL are being managed with TL1 for the same reasons that made it popular for their predecessors. Powerful TL1 OSSs like OPS/INE and NMA exist, it can used directly in craft interfaces, and it has a set of well-defined, powerful services lacking in alternatives like SNMP.
7) How does it compare to SNMP?
- TL1 is human-readable - SNMP uses has a binary encoded format called ASN.1. As a result it cannot be used as a craft interface. We humans can't read binary streams very well. TL1 by contrast is ASCII so what you see is what you get.
- TL1 provides standard services - SNMP lacks services like common management procedures for setting up performance or condition reporting schedules. SNMP makes agents dumb and managers overblown. TL1 has standard message sets/services for all management procedures from performance to security, testing to fault.
- TL1 offers alarm/event tracking - TL1 inserts an ATAG, a unique, sequentially increasing identifier in every event message sent from agent to manager. As a result, if a message is lost in transit the manager will know - the ATAG of the next event will not be in order. Unless so defined by a vendor, SNMP has no such message tracking. Did you lose an alarm/trap? How do you know?
8) Does TL1 follow the "Manager-Agent paradigm"? The "Manager-Agent paradigm" is an approach to equipment management. An "Agent" is an application which runs on the equipment and allows a management application or "Manager" running on a PC or workstation to control that equipment. Agents receive and perform commands sent by the manager and send unsolicited messages or events to the Manager based on the state of the equipment, for example, if there is a problem of some sort. TL1 (like SNMP) follows this paradigm. TL1 managers receive autonomous alarm messages when problems arise on a piece of TL1 managed equipment from a TL1 agent on that equipment. That agent processes TL1 commands received from a TL1 manager, allowing it to control a piece of equipment.
9) What is OSMINE? NE Vendors marketing their products to Service Providers must factor Telcordia's network integration process, known as OSMINE (Operations Systems Modification of Intelligent Network Elements) into their development plans. OSMINE is the process by which network equipment is certified to be compatible and interoperable with Telcordia Operations Support Systems (OSSs). Telcordia claims to have created 80% of the OSSs used by the RBOCs, and many Service Providers mandate that their equipment be OSMINE certified. For more information regarding the OSMINE process, visit www.telcordia.com.
10) Where can I get the TL1 Specification Documents? Bellcore was the original author of the TL1 specification. All TL1 standard documents are available directly from Bellcore, which recently changed its name to Telcordia Technologies. You can find more information about obtaining these documents on the Telcordia web site telecom-info.telcordia.com