  Peer to peer systems are the networks consisting of a group of nodes possible
to be as wide as the Internet. These networks are required of evaluation
mechanisms and distributed control and configurations, so each peer will be
able to communicate with other peers. Resilience to faults, failures and
attacks, are the main requirements of most communication systems and networks
today. Thus, since P2P networks can be individually used as an infrastructure
and an alternative for many other communication networks, they have to be more
reliable, and resilient to the faults, failures and attacks compared to the
client and server approach. In this work, we present a detailed study on the
behavior of various P2P networks toward faults and failures, and focus on
fault-tolerance subject. We consider two different static failure scenarios:
a)a random strategy in which nodes or edges of the network will be removed with
an equal probability and without any knowledge of the networks infrastructure,
b)a targeted strategy that uses some information about the nodes, and in which
the nodes with the highest degree have the most priority to be attacked. By
static faults, we mean a situation where the nodes or components encounter some
faults before the network starts to work or through its operation, and will
remain faulty to the end of the work session. Our goal is to introduce various
measures to analyzing P2P networks evaluating their vulnerability rate. The
presented criteria can be used for evaluating the reliability and vulnerability
of P2P networks toward both random and targeted failures. There is no limit to
the number and types of failures, the presented measures are able to be used
for different types of failures and even a wide range of networks.
