This document discusses web and social computing and peer-to-peer networks. It provides an overview of peer-to-peer network types including unstructured and structured networks. It also describes PeerSim, a peer-to-peer network simulator. The document outlines implementing maximum and minimum functions in PeerSim and analyzing the results. New methods were designed, run, and graphs of the outputs were generated to study how the maximum and minimum values changed over simulations.

1. Web and Social Computing
Speakers: Chandan ,Clement Robert and Kalthoom

2.  Objectives
 Peer to Peer Networks
 PeerSim
 Max and Min function Implementation and Results
 Conclusion
 Question & Answers

3. 1. Describe PeerSim functionality
2. Describe the different modes of PeerSim .
3. Design new methods ( Maximum and Minimum ).
4. Explain the out put results .

4.  A peer-to-peer network, P2P, is considered to be a
type of network architecture composed of
contributors that make their resources available to
other contributors on the same network without the
need for a server to oversee the transfer of
information.

5.  A peer-to-peer network’s architecture is generally formed dynamically by an ad-
hoc type of addition of nodes, meaning the loss of a certain node does not have a
significant impact on the rest of the network.
 This aspect of peer-to-peer networks gives the system the ability to easily scale to
any size that may be needed for a certain application.

6.  There are generally two major
types, Structured and
Unstructured. These two types of
networks also contain even more
specific underlying types of
networks.

7.  To be considered an unstructured
peer-to-peer network, the network
must not use any algorithm for
organization or optimization of
the network.
 For unstructured peer-to-peer
networks there are three different
models which include Pure peer-
to-peer networks, Hybrid peer-to-
peer networks, and Centralized
peer-to-peer networks.

8.  In a pure peer-to-peer network, or sometimes called a purely decentralized
network, all nodes are of equal ability meaning that there are no nodes that have
any special infrastructure function that could affect the network.
 A great example of a popular purely decentralized peer-to-peer network is the
Gnutella network. The main purpose of the Gnutella network is for that of a file
sharing system.

9.  Infrastructural nodes are
allowed to exist and are
often a type of central
directory server.
 All clients connected to the
network must connect to
one of these servers.
 Users connection
information and List of files
are saved in the central
server.

10.  Added Supernodes.
 These Supernodes are nodes
that are dynamically assigned
the task of servicing a small
subpart of the peer network by
indexing and caching files
contained therein.
 A popular example of this
centralized peer-to-peer
network is the file sharing
network Kazaa.

11.  Structured peer-to-peer networks generally hold the traits of using some type of
algorithm for organization or optimization of the network.
 Structured peer-to-peer networks use some type of global protocol to ensure that
any node in the network can proficiently route a search to some peer that has a
desired file.
 By far the most popular type of structured peer-to-peer network is the distributed
hash table or DHT.

12. • N nodes in the network
• Consistent hashing is used to assign keys and
values to nodes and resources
- SHA-1 hash of node’s IP address produces
160-bit ID
- SHA-1 hash of file produces 160-bit key, k
• Resource with key K is stored at node with ID=k
- If node with ID=k doesn’t exist then resource
is stored in the node with next highest available ID
• If node n joins the network
- Reassign keys from successor(n)
• If node n leaves the network
- Reassign keys to successor(n)

14.  Supplier vs Consumer Concept.
 Unlike Client/Server networks peers in P2P don’t rely one single source for
acquiring their necessities. Multiple Participants are involved.
 P2P is relatively cheaper to setup and simpler than client server networks.
 P2P can operate on a basic PC operating system whereas Client/ Server networks
require special OS.

15.  One of the major advantages to a peer-to-peer network is that each time a new
node is connected to the network the total capacity of the system increases.
 This point differs from the client-server model standpoint since the addition of
new nodes to a network that connects to a set of number of servers could possibly
slow data transfers for all of the connected users.
 Another advantage in regards to a pure peer-to-peer network is that there is no
single point of failure in the network.
 When compared to the client-server model on this point if the server fails the
network is brought down since the server is unable to relay information to the
connected nodes.

16.  One of the weaknesses of peer-to-peer networks is that of security. Generally
speaking peer-to-peer networks are more susceptible to security problems.
 Another disadvantage of peer-to-peer networks is the high bandwidth usage
required. This high bandwidth usage has lead to Internet Service Providers
starting to throttle, or limit, peer-to-peer traffic

17.  Simulating Peer-to-Peer (P2P) overlay networks is a common problem for
researchers and developers:
 need to be scalable .
 are highly dynamic .
 PeerSim :is one of the most known among researchers.

18.  A Peer-to-Peer simulator
 Is to use a modular approach, as the preferred way of coding with it is to re-use
existing modules:
 construct and initialize the underlying network modules.
 handle the different protocols modules.
 control and modify the network modules.
 The engines consist of components which may be 'plugged in' .

19.  Two different modes:
 Cycle-based :based on a very simple time scheduling algorithm and is very efficient and
scalable.
 Event-based :scheduled through events .

20.  protocols: used to define the behavior of the different peers.
 nodes: represent the peer themselves in the P2P network.
 controls: control the simulation by perform the global initialization and analysis:
 Initializer
 Dynamic
 Observers
 Linkable :interface used to access and manage node’s properties
 Add neighbor
 Get neighbor
 Node’s degree

21.  Every simulation is
configured with the help
of a configuration file :a
simple ASCII file

22. Simulator
• Main() Method
CDSimulator
nextExperment()
• loadInitializers()
• loadControls()
• execute()
Controls
Eg:
AverageObserver
s
Protocol n
IncrementalStats
Max, Min, Nmax,
Nmin, AVG etc
Protocol1 Protocol 2
Config File
• Set of Protocols and ordering
• Set of Controls and Ordering
• Set of Initializers + ordering
AverageFunction
• nextCycle()

23. Generated in Eclipse by ObjectAid UML Explorer

24.  How much free space does the network have to offer?
 What is the average lifetime of a node in the network?
 How many documents do nodes share on the average?
 Which node(s) performed the most searches?
 What is the maximum number of downloads that some node supported during a
session
 Etc
MAYANK BAWA, HECTOR GARCIA-MOLINA, ARISTIDES GIONIS, RAJEEV MOTWANI
“Estimating Aggregates on a Peer-to-Peer Network”
Stanford University, CA 94305 USA

26.  AverageObserver
 IncrementalStats

27.  Config File  Output: The Min Function Remains Constants and
the Max Values decreases towards the Min
value

28.  Config File  Results: Max Remains the same and Min increases
towards the Max Value
PeerSim Output

29.  Data taken in Excel  Graph generated

30.  Graph Generated Data taken in Excel

31.  Lessons Learnt (slide)
 Clear understanding of how Peer to Peer Networks work
 PeerSim provides an easy way to simulate P2P Protocols without wasting resources
 Java Programming Revised.
 Limitations
 The PeerSim Source codes are somehow complex to understand
 Some Protocols implemented in PeerSim need some time to understand

32. Q& A