Tech Note #37: Introduction to the TOAD
1998 Bionic Buffalo Corporation; All Rights Reserved.
12 June 1998
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Properties may be advertised with the objects, and specific property values or ranges may be
associated with requests. The use of properties in advertising and requests may considerably
reduce network traffic by eliminating unqualified responses.
A primary goal of the TOAD design was to reduce the level of message traffic. To this end,
messages are divided into segments, each of which may deal with different objects or classes. At
the beginning of the message is a simple header, which identifies the source and destination
Each message segment begins with the identifiers, classes, and properties about which that
segment is concerned. These qualifiers restrict the applicability of the rest of the segment.
Optionally, an initial segment can exist without such qualifiers. In such cases, the rest of the
initial segment applies to all objects and classes for the destination node or nodes.
Following the restriction (if any), is a verb identifying a function. There are four categories of
function: advertising, search, status, and control.
Advertising functions are used to announce the availability of objects. The segment prefix
describes which objects are being advertised, and tells their classes and properties.
Search functions are used to find objects. The object identifiers, properties, and classes of
the objects being sought are described by the segment prefix.
Status functions are used to ask or report on the status of the node itself, or on the objects it
Control functions are used to change the mode of operation of the destination node with
respect to the objects identified by the segment prefix.
There are no functions for binding objects to clients, for negotiations among clients and servers,
or for other operations expected to occur after the existence of a potential server object is known
to a would-be client. Those operations are done in ways that are specific to the objects
After the function verb, the segment may contain one or more tagged fields which contain
additional information about the request, the node, or the referenced objects or classes. The
most important of these are:
A lifetime is specified for all advertising, search, and control functions. After this lifetime,
the request or availability described by the segment will expire. Indefinite operation
requires periodic renewal of requests.