NTCIP is a suite of protocols that allow ITS field devices from multiple manufacturers to be controlled from a single Central system. One element of NTCIP that allows manufacturers and specifying agencies to clearly and precisely communicate the features that are supported by a field device is a Management Information Base, or MIB. A MIB is a text file that lists the objects and their supported ranges. It includes the functionality supported by the objects and is written so that it can be read by a Central system. Each NTCIP standard has a MIB that includes the mandatory and optional objects that are included in a particular standard. However, there are instances where a custom MIB is warranted.
Why create a custom MIB?
When a manufacturer has developed a new type of device or added a unique feature, one that is not standard, they often create a custom MIB. A custom MIB will accurately address the object and form the structure that supports the device’s feature. Many times, these MIBs include functionality that sets a device apart from the competition, or is a newly developed feature that is not able to be managed with a standard MIB.
Conversely, if an organization wanted to purchase a device that must include a particular non-standard feature, a custom MIB would allow them to clearly specify the functional requirements. By supplying a custom object to manufacturers, the company can communicate the exact unique functionality needed, rather than allow each manufacturer to create their own custom MIB.
A custom MIB can be written to increase the functionality provided by an existing standard MIB. In this case, the standard objects are not modified; the new custom MIB is written with objects that include the existing functionality as well as the expanded functionality. A custom MIB can also be created without reference to an existing NTCIP standard. This is typically the case when a device is not currently covered by NTCIP.
Formatting a MIB
MIBs are formatted in ASN.1 notation, which is a standard notation that describes the rules and structures of the MIB. The MIB provides information about the individual objects themselves and the object’s location within ISO Global Naming Tree. As an example, the standard dmsSignHeight object from the MIB for NTCIP 1203 – DMS is shown below.
dmsSignHeight OBJECT-TYPE
SYNTAX INTEGER (0—65535)
ACCESS read-only
STATUS mandatory
DESCRIPTION “Indicates the sign height in millimeters including the border (dmsVerticalBorder).
<Unit>millimeter
<Object Identifier> 1.3.6.1.4.1.1206.4.2.3.1.3”
::= {dmsSignCfg 3}
This object allows the Central system to query a sign to determine its physical height. The SYNTAX field, along with the DESCRIPTION field, indicates that the heights available for selection range from 0 to 65.535 meters. The ACCESS field shows that the Central system can only retrieve this object; if this were an object that the Central system could change, the ACCESS field would be set to “read-write”.The last line of the example shows the object’s location within the ISO Global Naming Tree. All of the objects in NTCIP are organized in a hierarchical fashion similar to a tree, where the ISO node is the root of the tree, to which nodes are attached like branches on a tree. Each object is then positioned like a leaf on the tree. In the example, dmsSignHeight is the third leaf (the “3” at the end of the Object Identifier) of node dmsSignCfg (the “1” just before the “3”).Custom objects are organized on the ISO Global Naming Tree under the creating organization’s assigned identification number. For example, the National Electrical Manufacturer’s Association (NEMA) identifier is 1206, and the Delcan Technologies identifier is 26, so the node under which Delcan Technologies custom objects are found is 1.3.6.1.4.1.1206.26.
Creating a Custom MIB
From a timing perspective, a custom MIB can be developed in a few days, or a few weeks, depending upon the scope of the added features. The number and size of features is the primary driver of that determination, as a larger, more complex project would require substantially more work and coding than a smaller project.If you have a project that would benefit from the creation of custom objects, Delcan Technologies can offer a superior level of expertise in this area. Delcan Technologies, a Parsons Company, is a world leader in design and implementation of ITS solutions. We partner with our clients as consultants, developers, and contractors to support them at all levels of a project. For more information on how we can help, contact us here.
