Transcript What is a Network?

Peer to Peer Network
Anas Hardan
What is a Network?
• A network is a group of computers
and other devices (such as printers)
that are connected by some type of
transmission media.
• Networks may be as small as two
computers connected by a cable in a
home office or as large as several
thousand computers connected across
the world via a combination of cable,
phone lines, and satellite links.

Why Use Networks?

•
•
•
•
•
•
Networks enable multiple users to:
Share devices like printers.
Data like spreadsheet files.
Sharing devices saves money.
Sharing devices also saves time.
Another advantage to networks is that
they allow you to manage, or
administer, resources on multiple
computers from a central location.
network models:
• Peer-to-Peer
• Client/Server


Peer-to-Peer Networks
• The simplest form of a network is a peer-to-peer
network.
• In a peer-to-peer network, every computer can
communicate directly with every other computer.
• Each computer can be configured to share only
some of its resources and keep other resources
inaccessible to the network.
• Every computer has the ability to send and receive
information from every other computer.
Peer-to-Peer Networks
P2P File Sharing Networks


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.
How second generation P2P
services worked

Gnutella2: Hubs are used to quickly search for
files, eliminating the original "find peer and
search" method. Instead, they store a list of files
on all the "Leaves" (A peer) that are connected to
it, thus dramatically reducing search time.
Advantages: if a hub crashes, it's network stays
alive.
Disadvantages: Doesn't make network any more
durable than the first generation of P2P.
Gnutella2: www.gnutella.com

FastTrack: Programs such as Kazaa and iMesh
use the FastTrack protocol. Normal peers connect
to a super node which acts just like a hub. Super
nodes also connect to other super nodes,
allowing search requests to move through the
network very quickly. Peers then establish a
direct connection to a client after a file has been
found.
Advantages: Any client can become a super
node.
Disadvantages: Corruption of files occur.
Clients include: Kazaa (www.kazaa.com), iMesh
(www.imesh.com)

BitTorrent: .torrent files are used to store
information about the file being shared. Once a
torrent file is opened, the client connects to the
tracker which tells the client where the file is
located and what other peers/seeders there are.
BitTorrent works by chunks of small files being
transferred (even through multiple connections),
while you are downloading. The files are checked
for corruption as the download continues. Leeches
are people who download and don't upload, and
are highly frowned upon on some sites,
disallowing them from downloading any further.
Advantages: Very fast.
Disadvantages: Trackers are unreliable and if it
goes down, the file is lost.

EDonkey Network: Edonkey runs on
the same principle as first generation
P2P, only anybody can become a
server. Clients communicate with the
server to download files, and random
chunks can be downloaded in any
order then put together in the end.
Advantages: No file corruption, leech
penalization.
Disadvantages: It can penalize users
unfairly.
EDonkey: www.edonkey2000.com
The advantages
• They are simple to configure.
• They are typically less expensive
to set up and maintain than other
types of networks.
 Users control individual shared
resources.
 No need of a network
administrator.
disadvantages
• They are not very flexible - As a peer-topeer network grows larger, adding or
changing significant elements of the
network may be difficult.
• They are also not necessarily secure meaning that in simple installations, data
and other resources shared by network
users can be easily discovered and used by
unauthorized people
• They are not practical for connecting more
than a handful of computers, because they
do not always centralize resources.