Download Peer to peer (P2P) network

Peer to peer (P2P) network
ISYM 540
Current Topics in Information System
Management
Anas hardan
Introduction
P2P networking has generated tremendous interest worldwide among both Internet
surfers and computer networking professionals. P2P software systems like Kazaa and
Napster rank amongst the most popular software applications ever. Numerous businesses
and Web sites have promoted "peer to peer" technology as the future of Internet
networking.
Although they have actually existed for many years, P2P technologies promise to
radically change the future of networking. P2P file sharing software has also created
much controversy over legality and "fair use." In general, experts disagree on various
details of P2P and precisely how it will evolve in the future.
Traditional Peer to Peer Networks
The P2P acronym technically stands for peer to peer. P2P is a type of network in which
each workstation has equivalent capabilities and responsibilities. This differs from
client/server architectures, in which some computers are dedicated to serving the others."
This definition captures the traditional meaning of peer to peer networking. Computers in
a peer to peer network are typically situated physically near to each other and run similar
networking protocols and software. Before home networking became popular, only small
businesses and schools built peer to peer networks.
Architecture of P2P systems
The P2P overlay network consists of all the participating peers as network nodes. There
are links between any two nodes that know each other: i.e. if a participating peer knows
the location of another peer in the P2P network, then there is a directed edge from the
former node to the latter in the overlay network. Based on how the nodes in the overlay
network are linked to each other, we can classify the P2P networks as unstructured or
structured.
Structured peer-to-peer systems
Structured P2P network employ a globally consistent protocol to ensure that any node
can efficiently route a search to some peer that has the desired file, even if the file is
extremely rare. Such a guarantee necessitates a more structured pattern of overlay links.
By far the most common type of structured P2P network is the distributed hash table
(DHT), in which a variant of consistent hashing is used to assign ownership of each file
to a particular peer, in a way analogous to a traditional hash table's assignment of each
key to a particular array slot.
Unstructured peer-to-peer systems
An unstructured P2P network is formed when the overlay links are established arbitrarily.
Such networks can be easily constructed as a new peer that wants to join the network can
copy existing links of another node and then form its own links over time. In an
unstructured P2P network, if a peer wants to find a desired piece of data in the network,
the query has to be flooded through the network to find as many peers as possible that
share the data. The main disadvantage with such networks is that the queries may not
always be resolved. Popular content is likely to be available at several peers and any peer
searching for it is likely to find the same thing. But if a peer is looking for rare data
shared by only a few other peers, then it is highly unlikely that search will be successful.
Since there is no correlation between a peer and the content managed by it, there is no
guarantee that flooding will find a peer that has the desired data. Flooding also causes a
high amount of signaling traffic in the network and hence such networks typically have
very poor search efficiency. Most of the popular P2P networks are unstructured.
In pure P2P networks: Peers act as equals, merging the roles of clients and server. In such
networks, there is no central server managing the network, neither is there a central
router. Some examples of pure P2P application layer networks designed for file sharing
are Gnutella (pre v0.4) and Freenet.
There also exist hybrid P2P systems, which distribute their clients into two groups: client
nodes and overlay nodes. Typically, each client is able to act according to the momentary
need of the network and can become part of the respective overlay network used to
coordinate the P2P structure. This division between normal and 'better' nodes is done in
order to address the scaling problems on early pure P2P networks. Examples for such
networks are for example Gnutella (after v0.4) or G2.
An other type of hybrid P2P network are networks using on the one hand central server(s)
or bootstrapping mechanisms, on the other hand P2P for their data transfers. These
networks are in general called 'centralized networks' because of their lack of ability to
work without their central server(s). An example for such a network is the eDonkey
network (eD2k).
P2P File Sharing Networks
When most people hear the term "P2P", they think not of traditional peer networks, but
rather peer to peer file sharing over the Internet. P2P file sharing systems have become
the single most popular class of Internet applications in this decade.
A P2P network implements search and data transfer protocols above the Internet Protocol
(IP). To access a P2P network, users simply download and install a suitable P2P client
application.
Numerous P2P networks and P2P software applications exist. Some P2P applications
work only with one P2P network, while others operate cross-network. Likewise, some
P2P networks support only one application, while others support multiple applications.
Navigating a P2P Network
This diagram shows how a P2P network operates. The solid lines indicate physical, hardwired network cables. The dotted lines indicate that each PC can communicate and share
files with every other PC on such a network. A printer attached to one PC can be used by
other PCs on the network—if that printer’s PC allows such use.
What Are P2P Software Applications?
A good definition of P2P software was proposed by Dave Winer of UserLand Software
many years ago when P2P was first becoming mainstream. Dave suggests that P2P
software applications include these seven key characteristics:
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the user interface runs outsides of a Web browser
computers in the system can act as both clients and servers
the software is easy to use and well-integrated
the application includes tools to support users wanting to create content or add
functionality
the application makes connections with other users
the application does something new or exciting
the software supports "cross-network" protocols like SOAP or XML-RPC
In this modern view of peer to peer computing, P2P networks stretch across the entire
Internet, not just a home local area network (LAN). Easy-to-use P2P software
applications allow both geeks and non-technical people to participate.
Privacy and Security on Peer-to-Peer File-Sharing
Networks
Peer-to-peer file-sharing systems are powerful tools for sharing information with millions
of other people around the world. People who install these tools need to be aware of the
potentially serious privacy risks that may come from their use or misuse.
In many respects the problems facing peer-to-peer users are akin to the problems
facing any speaker on the Internet. For example, someone who creates a website to share
family pictures could inadvertently place sensitive files or pictures they don't wish to
share on their site. Many of us have a favorite story about someone who sent an
embarrassing email message to a mailing list by mistake.
Security Risks
Users of P2P file-sharing systems face many of the same security risks as other Internet
users. Just as in other applications, P2P users must take care to only run programs from
sources that they trust, and should be careful to check for viruses. They should safeguard
their computer from attack when online. File sharing adds an extra dimension to these
concerns due to the quantity and frequency of files traded the relatively unsophisticated
user base, and the rise of self-help systems to prevent copyright infringement. At this
time, P2P file-sharing applications are not known to be any less -- or any more -securing than Internet applications on the market in other areas.
Viruses - Because peer-to-peer file sharing networks enable files to be transferred
among millions of computers -- most of which are owned and operated by total strangers
there is an ever-present risk that files downloaded from a peer-to-peer file sharing
network could carry various kinds of malicious software like viruses and "worms."
It is, of course, possible to receive a dangerous file in numerous ways, such as over
the Web or by e-mail. The best protection against viruses continues to be the use of upto-date anti-virus software. 100% protection can never be achieved, but users should be
aware that to download files without adequate protection opens them up to substantial
risks.
Online Attacks - When peer-to-peer networks identify shared files to millions of
users, they also identify the location of a user's computer, and could even target that
computer's IP address (Internet Protocol address) with attempts to gain access. This is not
a risk unique to peer-to-peer file sharing networks; all Internet communications involve
an exchange of IP addresses. But because peer-to-peer file sharing networks search
millions of computers, they can provide access to millions of IP addresses.
Self-Help Attacks - A new form of security threat may be growing for peer-to-peer
users in the rise of self-help techniques by copyright holders concerned about
infringement on file-trading networks. More benign versions flood P2P networks with
bogus copies of copyrighted works in order to fool people into downloading or storing
them.
Advantages and weaknesses of P2P networks
In P2P networks, all clients provide resources, which may include bandwidth, storage
space, and computing power. As nodes arrive and demand on the system increases, the
total capacity of the system also increases. This is not true of client-server architecture
with a fixed set of servers, in which adding more clients could mean slower data transfer
for all users.
The distributed nature of P2P networks also increases robustness and in pure P2P systems
by enabling peers to find the data without relying on a centralized index server. In the
latter case, there is no single point of failure in the system.
As with most network systems, unsecure and unsigned codes may allow remote access to
files on a victim's computer or even compromise the entire network.[citation needed] In
the past this has happened for example to the FastTrack network when anti P2P
companies managed to introduce faked chunks into downloads and downloaded files
(mostly mp3 files) were unusable afterwards or even contained malicious code.[citation
needed] Consequently, the P2P networks of today have seen an enormous increase of
their security and file verification mechanisms. Modern hashing, chunk verification and
different encryption methods have made most networks resistant to almost any type of
attack, even when major parts of the respective network have been replaced by faked or
nonfunctional hosts.
Usually Internet providers (ISPs) don't welcome P2P users in their networks. The reason
is that P2P clients tend to increase the traffic. Compared to Web browsing, e-mail or most
other uses of the internet, where data is only transferred in short intervals and relative
small quantities, P2P consists usually in a relatively heavy use of the internet connection
due to the ongoing file transfers and swarm/network coordination packets.
A possible solution to this is called P2P caching, where an ISP stores the part of files
most accessed by P2P clients in other to save access to the Internet.
Conclusion
A peer-to-peer network is sometimes the perfect (and cheap) solution for connecting the
computers at a small nonprofit. However, peer-to-peer networking has its limitations, and
your organization should tread with caution to avoid headaches -- security issues,
hardware inadequacies, backup problems.
References
Peer-to-Peer Based Resource Discovery in Global Grids : A Tutorial http://www.cs.mu.oz.au , June
10, 2007, July 9, 2009 .
P2P Networking and P2P Software, http://compnetworking.about.com, Dec 2006, July 6, 2009
Peer-to-Peer Network, http://www.computerworld.com, April 8, 2002,july 7 2009
Peer-to-Peer File Sharing Privacy and Security, http::/www.cdt.org, May 15, 2003, July 9, 2009
Foundation of Peer-to-Peer Computing,http://www.sciencedirect.com/science/issue/5624-2008999689997-678759, 5 February 2008, July 6, 2009.