Access Identifier (AID) is one of the staging parameter blocks of TL1 input messages. The parameters of AID uniquely identify an entity in the NE on which the command takes effect. For example an AID might identify a slot, or a chassis, or the cross connect level, or the NE itself.

AID modeling is the process of naming the entities of the NE with uniquely identifiable terminologies so that the NE is easy to manage. AID modeling gains importance as the NEIR document requires complete description about AIDs. The NEIR document submission is part of the OSMINE certification process.

Classification of Access Identifiers

The access identifiers are of two types. One is the physical identifier and the other is functional identifier. The main difference between these two types lies in the way of identifying the entity. A physical AID identifies the entity by its location in the NE. A functional AID identifies the entity by its usage in the NE.

How to model the Access Identifiers

There are no hard and fast rules on modeling the access identifiers. Still it is better to model the identifiers with some the best practices as shown below.

• Equipment AID
• Facility AID
• Cross-connect AID
• Identifier Key

Equipment AID - Modeling the Equipment Unit as the Access Identifier

You can model the equipment unit as the AID. Equipment AID enables the NE to identify the particular equipment unit to which a message pertains. An equipment unit can be as large as the entire NE or as small as a single element. 

The equipment AID can be either functional or physical. 

• For modeling a functional equipment AID the best way is to make the equipment unit's name, as specified  by  the  supplier, as the access identifier. Examples of  equipment AIDs modeled on the above mentioned basis are 


CC1 - For the Common Control unit number  1 
PWRA - For Power unit  A. 
 

• For modeling a physical equipment AID the location of the equipment unit is necessary. In case of a switch the arrangement of equipment units are hierarchical. This hierarchical arrangement can be used to model the physical equipment APD as shown below


<frame>-<shelf>-<slot>    - This is an example for physical equipment AID.

A facility AID may be based on the rates of the transmission hierarchy supported by the NE, a physical location, or some other system. 

For facility AIDs based on the transmission rate hierarchy, the highest transmission rate takes the first level. It is followed by the other levels till the level of the specific facility/circuit specified by the value of modifier.  It is necessary to spicy the transmission rate hierarchy for accessing a facility/circuit in a particular supplier's NE. All OSSs that interface with the NE use this transmission rate hierarchy. 

Example :
In a hierarchy-based facility/circuit AID for an NE that terminates  DS3-level facilities and allows for the access of the DS1 facilities and DS0-level circuits. A single DS0  in such an NE could be addressed with a compound AID value as follows: 
<ds3>-<ds1>-<ds0> 

Example : 
4-2111  -  Where 4 indicates the 4th DS3 facility, 21 indicates the 21st DS1 facility on this DS3 facility, and 11 indicates the 11th DS0 within this  DS1 facility. 

CrossConnect AID - Modeling the cross connecting of two channels as the Access Identifier

Cross connecting two channels calls for two access parameters - one representing the FROM channel and the other the TO channel. The AID values for this case are of the form: 

[FROM=]<channel no.>,   [TO=]<channel no.> 

where, <FROM> -  Indicates an identifier at one end of cross connection and <TO> -  Indicates an identifier at other end of cross connection. 

Example : 
STS-3-2 , STS-4-3
In the above example cross connecting takes place between STS-3-2 and STS-4-3. Here STS indicates that the signal is a Synchronous Transfer Signal STS, the number 3 indicates VT group (virtual tributaries group)  and 2 indicates VT.

IdentifierKey AID - Modeling the Identifier Key as the Access Identifier

In some cases, you use AID as a key to identify a particular or a set of objects from the object group. For example, operators specify ON (order number of the delayed activation message stored in the NE) as the AID, for retrieving or deleting a pending delayed activation message.  

The key can be simple , list and range. 
Simple Key : 
The AID  for simple key is as follows, 
<order number>  - Indicates the order  number of  the pending delayed activation message. 
RTRV-DA::4:1::;  -   Retrieves delay activation message  with order number 4. 

List Keys : 
To retrieve the list  of pending delayed activation messages from NE, specify the keys as shown below 
<on1> & <on2> &<on3>&<on4>    - Indicates the order  number of  the pending delayed activation messages to be retrieved.. 
RTRV-DA::4&7&8:1::; - Retrieves delay activation messages of order number 4&7&8