Self-Configuration and Administration of Wireless Grids - Cloud, Grid and High Performance Computing: Emerging Applications - page 265

GRID OPERATION status of the emergency workers, to efficiently

distribute critical data they may possess, and to
better coordinate the activities. Node Management

Node Entry or Exit Node Discovery

Mobile nodes register <address, name> tuple with
the Root Station (RS) as they enter the network
under the RS coverage. Node sends an enter_node
message. If the node cannot directly establish con-
nection with the RS, it uses multiple hops to pass
on the registration information. This can happen in
a setup where the wired node (RS) is out of opera-
tion or when reach and wireless signals are weak
in strength. When the RS receives the request, it
sends enter_node response to the node and adds
the information related to the node. The response
includes the information about RS and AO. For
example, in an emergency situation, appropriate
personnel such as police or fire workers may ar-
rive or leave the site. A local cluster can be formed
to handle both voice and data communications.
Entry and exist messages can help to maintain the

A chain-of-responsibility pattern (Gamma et. al.,
1995) is used for node discovery. A node N o sends
a discover_node request to RS o seeking connec-
tion to a different node N a . The request contains
the name of the requested node. RS o looks up its
AO o information to locate the node and sends
a discover_node response to node N o with the
address information of N a . If node N a does not
exist in the AO o then RS o sends the discover_node
request to the BS o . This request includes the RS o

Figure 4. Message format

Table 2. Message header fields

Header Field Description

Message Id The unique message id for the message

Opcode The operation code for the message.

Send/Response Flag. A flag indicating whether the message is a send request or response to a
send request

S/R flag

Table 3. Opcode values

Opcode Values Brief Description

Enter_node Informs members of the entry of the node

Leave_node Informs member of the exit of the node

Enter_RS Informs members of the entry of the RS

Leave_RS Informs member of the exit of the RS

Enter_BS Informs members of the entry of the BS

Leave_BS Informs member of the exit of the BS

Discover_node Used to discover node

Hello Used to verify if the members exist