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2.0 TL1 – The Telecom Management
Protocol
TL1 is the widely used
telecom management protocol with the following advantages over other protocols.
Standard Command Line Interface:
Being ASCII, human operators can compose input message and directly interpret
responses and events. Unlike many other CLIs, TL1 is not free form, with
the syntax of one command differing from the next. As a result, element
managers use the same TL1 interface.
Man-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.
Delayed Activation: Delay Activation
is a function whereby an input message (request) can be stored in a Message
Pending buffer at the NE, for final execution later, either automatically
or by a subsequent message from the OS.
Autonomous Message Tracking: ATAG
(Autonomous Message Tag) in autonomous message allows an OS to determine
if it has failed to receive any spontaneous outputs by checking for omissions
in the sequence of messages received.
Acknowledgment: An acknowledgment
is a brief output message generated in response to an input command message.
As per the standards, an acknowledgment should be used if an output response
message to the command cannot be transmitted within 2 seconds of its receipt.
2.1 TL1 and SNMP: A comparison
The following table highlights some of the key differences between TL1 and SNMP (Simple Network Management Protocol), a popular protocol in the data centric domain
| S. No |
Functions & Features |
TL1 |
SNMP |
| 1. |
Operations :
Operations are the actions initiated by manager to manage
the managed objects. |
Input Messages. It may operate on some data or it may initiate
some action in NE. |
GET,SET ,GET-NEXT and GET-BULK
Here, all requests will operate on data. |
| 2. |
Notification :
A notification is one generated by the NE either on a periodic timed
basis or to report some unusual occurrence. |
Autonomous Message |
Trap |
| 3. |
Management Information Model :
Abstract representation of managed object. |
There is no such information model used in TL1. Here every thing
is action to be taken at NE. |
The Internet Structure of Management Information (SMI) defines
the rules for how management information is described and stored. Here ,
it is called as MIB (Management Information Model). |
| 4. |
Encoding:
Transforming the messages that are sent over communication channel. |
There is no encoding here. TL1 messages are in plain ASCII text. |
ASN.1 encoding is used here. |
| 5. |
Notification Tracking:
Provision in notification that allows an OSS to determine if it has failed to receive any spontaneous outputs by checking sequence numbers |
ATAG in autonomous message allows an OSS to determine if it has failed to receive a spontaneous output by checking sequence numbers. |
Inform can be used by agent for Confirmed Notification. After an Inform message is sent out, the agent will confirm receipt of the same with a response message. |
| 6. |
Acknowledgment:
An acknowledgment is a short reply from the NE indicating that an input
command message is being acted upon or has been immediately rejected. |
Yes |
No |
| 7. |
Delay Activation:
Delay Activation allows execution of a request at pre-determined time. |
Yes |
No |
| 8. |
Security :
Security is concerned with protecting managed resources from
unauthorized access. |
It can be implemented by using system and resource access control
mechanism. System access control needs persistent connection between OSS
and NE for authentication (System access control). |
SNMPv3 uses USM (User Security Model) and VACM (View based
Access Control Mechanism) security model. Here, authentication
is done per message.
So connection between OSS and NE may be persistent or not. |
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