background image
Tech Note #37:  Introduction to the TOAD
1998 Bionic Buffalo Corporation; All Rights Reserved.
                  12 June 1998
4 of 13
The motivation behind TOAD was to allow the smallest devices to operate easily, both in small
and in large networks. A TOAD-compliant device will use simple broadcast mechanisms in
small networks, but will be subservient to a hierarchy when so instructed by a management
node. To reduce software complexity in small devices, many message formats are common to
the two behaviours: only the transmission mode (broadcast or unicast) is changed.
The changeability of the protocol from one node to another node is defined separately for the
different objects in a node. A node might use one mode for certain objects, and another mode
for other objects.
Modes of Operation
A TOAD node operates in one of seven modes. Each mode of operation is explained in the
A node may operate in one mode for some of the objects it contains or seeks, and in another
node for other objects.
Mode 0: Quiet Mode
In Quiet Mode, the node does not advertise or seek objects. It generates no network
traffic, and fails all internal requests for discovery. (It will, however, respond to certain
status requests.)
Quite Mode is entered as a result of explicit instruction, or due to some failures. The
use of intentional entry into Quiet Mode is for debug purposes, or to synchronize
updates of multiple objects which must have coherent versions.
Mode 1: Internal Mode
When in Internal Mode, the node allows internal requests to discover and advertise
objects, but keeps all information inside the node. No network traffic is generated
except for responses to certain status requests.
Internal Mode effectively allows local operation, taking the node off the network.
Mode 2: Passive Mode Mode
In Passive Mode, the node will use information acquired by listening on the network,
but will not actively seek information about specific objects. If the node learns, by
listening on the network, that a certain object exists, the node may attempt to use that
object. However, it will not send messages to look for an object of any particular class,
or for any specific object.