Incentives - Peer-to-Peer Computing: Applications, Architecture, Protocols, and Challenges - page 120

FIGURE 5.21: Number of subscribed stripes versus the type of a client
(n = 10).

5.3.4.2 Two Neighboring Clients

JTUSJQFT
GSPNTFSWFS

J T K T

G T G T

JTUSJQFT

JTUSJQFT

x y x y

KTUSJQFT

(a) (b)

FIGURE 5.22: A scenario with two neighboring clients. (a) Master-slave.
(b) Peer-to-peer.

First, let us consider a simple scenario with two neighboring clients:{x, y}.
There are two cases: (1) x and y form a master-slave relationship, as shown
in Figure 5.22(a); (2) x and y form a peer-to-peer relationship, as shown in
Figure 5.22(b).
Without loss of generality, let us assume that x is the master while y is
the slave. As depicted in Figure 5.22(a), x subscribes to i stripes from the
server and sends them to y through the peer interface. In this case, x is an
enthusiastic client, serving y at the expense of its own energy resources. This
requires that the type of master x should satisfy: α x ≥α M (i), where α M (i)
is given by:

E RX
s

(i) + E T X
p

(i)

α M (i) = (5.51)

E RX
s

On the other hand, client y may decide to “free-ride” because its residual
energy is low. This requires that the type of slave y should satisfy: α y ≥α S (i),