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Tech Note #37:  Introduction to the TOAD
1998 Bionic Buffalo Corporation; All Rights Reserved.
                  12 June 1998
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Traffic Control and Caching
To control the amount of traffic on the network, broadcast advertisements and requests are sent
at intervals. The intervals are chosen based on the application, since some environments change
more or less frequently than others. Intervals are defined by the node making the transmission,
but can be altered by another node using commands in the protocol.
For example, a node may advertise at 3-second intervals by default, but this might be changed
to 10-second intervals at the request of a management routine on another node.
Each node may cache information received, so the node can respond immediately to a request.
Using the cache, the node does not need to wait until an advertisement or response is received.
The designer of a node may optimize use of the cache, by limiting the types of information
cached, the duration of caching, or other parameters.
Every advertisement, request, or other parameter is given a lifetime. The advertisement,
request, or other parameter expires after the specified lifetime, or when superseded by a
different value.
The limited lifetime also applies to commands to change modes. If a node is commanded to
enter Passive Mode, the command will be effective only for a specified period of time. After the
Passive-Mode command has expired, the node will return to the default Request Mode.
Commands must therefore be renewed periodically. This prevents the network from “locking
up” if a management node fails or if some portion of the network is lost.
Service Negotiation
The TOAD protocol serves only to advertise the existence of, or the requirement for, objects. It
does not participate in negotiations for service. Once an object is located, it is up to the client to
petition the service object for action.
To facilitate the negotiations among clients and servers, TOAD does permit advertising object
properties. Properties are named, typed values, which are dynamically associated with specific
objects. An object defines the existence and values of its own properties, using the handle
returned by the object registration call.
Properties are named using simple character strings.
TOAD supports two kinds of properties: certain standard properties defined by TOAD itself,
and any other properties defined by the object.
The standard TOAD properties include class, identifier, availability, usage, version,
performance, and manufacturer.