Lecture 22: Network Management #2

Object Identifiers

ASN.1 might be of only passing interest were it not for the OBJECT IDENTIFIER data type. An OBJECT IDENTIFIER is a simple ASN.1 data type with special properties.

An OBJECT IDENTIFIER is a data type denoting an authoritatively named object, regardless of the type of the object which it names. The (somewhat hubristic) notion here is that provides a naming scheme allowing us to specify names of things, in a global sense, such that everything that there is in the universe^[2] can have a globally-unique name.

It is written as a sequence of non-negative integer values which describe a traversal of a tree. The tree consists of a root connected to a number of labelled nodes via edges. Each label consists of a non-negative integer value and an optional brief textual description (or Object Descriptor associated with it). The most common format for writing down the value of an OBJECT IDENTIFIER is as a dotted sequence, thus:

1.0.8571.5.1

This identifies the object found by starting at the root, moving to the node with label 1, then moving to the node with label 0, and so on. The node found after traversing this list is the one being identified. Other formats for describing OBJECT IDENTIFIERS are also used, see later.

^[2] More correctly, we should probably say every kind of thing in the universe has a unique name, instead of "every thing".

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