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Architecture of Computing Systems (Lecture Notes in Computer ...

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Effect <strong>of</strong> the Degree <strong>of</strong> Neighborhood on Resource Discovery 179<br />

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Fig. 2. Neighborhood on the <strong>in</strong>frastructural spectrum. (a) Completely decentralized<br />

degree=4. (b) Completely decentralized degree=6.<br />

<strong>of</strong>fers to the matchmaker. The matchmaker f<strong>in</strong>ds matches for resource requests<br />

from received resource <strong>of</strong>fers and <strong>in</strong>forms the matched consumer/producer nodes.<br />

As all participat<strong>in</strong>g consumer/producer nodes can send their request/<strong>of</strong>fer message<br />

to the matchmaker only, therefore the neighborhood <strong>of</strong> a consumer/<br />

producer node is n (n be<strong>in</strong>g the total number <strong>of</strong> the nodes <strong>in</strong> the ad hoc grid).<br />

This is represented <strong>in</strong> Figure-1a, where there is only one matchmaker.<br />

In the multiple adaptive matchmakers approach, an <strong>in</strong>termediate centralized<br />

approach us<strong>in</strong>g multiple adaptive matchmakers, each consumer/producer<br />

node is under the responsibility <strong>of</strong> one matchmaker at any given po<strong>in</strong>t <strong>in</strong> time. The<br />

matchmaker is demoted or promoted accord<strong>in</strong>g to the workload <strong>of</strong> the<br />

matchmaker(s) <strong>in</strong> the ad hoc grid. Then number <strong>of</strong> matchmaker(s) and the responsible<br />

matchmaker <strong>of</strong> a consumer/producer node may also change by the promotion/demotion<br />

<strong>of</strong> the matchmaker(s) [12]. As each consumer/producer node is<br />

under the responsibility <strong>of</strong> only one matchmaker at any given po<strong>in</strong>t <strong>in</strong> time, therefore<br />

the neighborhood <strong>of</strong> a consumer/producer nodes is n/m (n be<strong>in</strong>g the total number<br />

<strong>of</strong> the participat<strong>in</strong>g nodes and m be<strong>in</strong>g the number <strong>of</strong> matchmakers). This is<br />

represented <strong>in</strong> Figure 1b, where multiple matchmakers are represented with different<br />

colors and the consumer/producer nodes <strong>in</strong> each zone are represented by<br />

the color <strong>of</strong> their responsible matchmaker.<br />

In the completely decentralized (P2P) approach, where every node is<br />

its own matchmaker, each node looks for the appropriate resources from all the<br />

nodes <strong>in</strong> its degree <strong>of</strong> neighborhood. The ad hoc grid is implemented on top <strong>of</strong><br />

Pastry [15], a structured P2P overlay network. The degree <strong>of</strong> neighborhood <strong>of</strong><br />

a node is implemented and varied with the help <strong>of</strong> Pastry node’s leaf set [15] <strong>in</strong><br />

our ad hoc grid, which is expla<strong>in</strong>ed below.<br />

We consider a Pastry node with nodeID x for expla<strong>in</strong><strong>in</strong>g the degree <strong>of</strong> neighborhood<br />

<strong>in</strong> the ad hoc grid. Each node <strong>in</strong> Pastry is assigned a 128 bits unique<br />

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