Assigning an ASN.1 file to a Message

An ASN.1 schema file may be assigned (associated) with a BER or DER ASN.1 message by using this command. ASN.1 files are assigned to PER messages when they are created or opened because they are required to understand the content of the message. Assigning an ASN.1 schema file will provide symbolic element names and type information for the content items within the message. It will also enable the editing of fields within the message.

1. Click the ASN.1 option from the main menu toolbar.

2. Select the Assign ASN.1 option to open a find dialog.

Alternately, the Assign ASN.1 toolbar icon can be used:

3. The file navigation dialog box will be displayed allowing the selection of an ASN.1 file.

Note: These files must contain ASN.1 definitions only. Multiple ASN.1 files may be selected if the message being described requires multiple schemas (for example, if a given ASN.1 file imports definitions from another file). It is also possible to select only the main schema file containing the PDU type definition as long as all dependent import files are present in the same directory. If import files exist in different directories, then the Assign All Items Wizard command must be used.

4. ASN1VE will attempt to compile the selected ASN.1 files. If the ASN.1 files have syntax errors, then the following dialog window will be displayed:

Pressing the OK button will dismiss the window. Details on the specific errors are output to the error log window in the lower right area of the display:

The user must then correct the syntax errors in the ASN.1 file and then the operation may be retried.

5. After successful compilation of the ASN.1 file(s):

If a single matching PDU type is found in the schema that matches the current message being displayed, then ASN1VE will decode the message using the matched PDU type and the view will be switched to element view completing this operation.

6. If multiple matching PDU types are found, then ASN1VE will prompt the user to select a PDU type using the Select PDU type dialog:

Display Possible PDU Types and Display All Types radio boxes will be displayed with the list of module names in the selected ASN.1 specifications. Each module will contain a list of type names in that module.

The Display Possible PDU Types button selection will show only those types that are most likely to be used for a new message. This is defined to be all types in the module that are not referenced by any other types and which match the initial tag on the message. If no types meet this criteria, then no types will be displayed in this list.

The Display All Types selection will display all of the types for each module.

7. If the user select a type and presses OK, ASN1VE will try to decode the message with the user-selected PDU type and the view will be switched to element view if decoding is successful. The user may also press the Cancel button at this point to cancel the operation.

NOTE: If the ASN.1 files are of the older 1990 version (X.208), then the "Assign ASN.1 Wizard" command must be used instead of this command.