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[7] developed a cooperative model of CP (” Content Provider ”) and ISP, which
aimed at co-optimization by sharing control between the ISP and the CP. This
study analyzed the optimality of this model by using the game theory and com-
pared this model with the traditional model by means of simulations. The simu-
lation results showed the advantages of the sharing model under circumstances
with different congestion levels, and pointed that under some conditions, if the
complete network information is shared without any co-optimization control, the
co-benefits of the CP and the ISP may be lower than before the sharing of the
complete network information.
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Fig. 1. The interactive between iTracker and P2P
2 Improved Cooperative Model and Theoretical Analysis
2.1 P4P
In the P4P model, each ISP maintains an iTracker for its network, and the
iTracker has multiple interfaces for ISPs to communicate with P2P applications
with respect to the following: (a) static network policy, (b) P-distance mirroring
network policy and status, and (c) network capacity. The main interfaces are
shown in Figure 1, where the P-distance interface is the core of P4P. Through
the P-distance, an ISP can communicate to the P2P applications the current cost
of its intradomain and inter-domain links. The P-distance reflects a network's
preference and status with respect to the application's cost. The main algorithm
of P-distance is the min-max link utilization with a distributed algorithm as
follows:
b e +
k
t ij I e ( i,j ) /c e ,
min
∀k : t k ∈T k
max
e∈E
(1)
i
j
where b e is the background trac (i.e. trac that P4P can't control), c e is the
capacity of link e , I e ( i,j ) is the indicator link e on the route from PID
i to
j ,and T k denotes the set of all feasible trac solutions on the basis of the
demand and the property of the P2P applications session k . t k =( t ij ), where t ij
denotes the trac from PID
PID
j in the P2P session k .
The above mentioned PID (opaque ID) is a virtual network point. There are
many types of PIDs, one of which is an aggregation point, i.e. a PID represents
i to PID
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