Peer to Peer Architecture in Computer Networks, Study notes of Computer Networks

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Program Name :B.Tech

Semester :ECE 6th Sem

Course Name: Computer Network

Course Code:EC 602

Facilitator Name: Megha Dewan

What is Peer to Peer Architecture?



Peer to peer is a type of architecture in which nodes are

interconnected with each other and share resources with

each other without the central controlling server.



P2P system allows us to construct such a distributed system

or a application in which all resources and data is contributed

by the hosts over the network.



P2P system allows us to sharing of data at very large scale

without the use of any server whose job is to manage the

scaling it means that scaling of data can be done without a

server.



P2P are used in Filesharing,webcaching and providing

information to user , Bittorrent and etc are examples of P2P

applications which use P2P architecture.

Advantages of Peer to Peer



It is easy to install.



All resources are shared by all nodes

with each other without a server.



Central dependency is eliminated.



It is more reliable.



Cost of building and maintaining this p2p

network is less as compared to other

network.

Disadvantages of Peer to Peer



As we no there is not central server so that

network cannot be administrated for example we

cannot filter the files being shared by the nodes

with each other.



Security is an other issue in this network as

malware can easily be transmitted across the

network.



Because of no centralized server we cannot make

a backup of system every node has to make

backup of its own data in his system.



Transferring of sensitive data through the p2p is

not recommended.

Peer to Peer Models

 Purely Decentralized System

 Centralized System

 Hybird System

Purely Decentralized Model:

It is a type of model in which there is not central sever all nodes are acting as both client and server all are getting

and sending data to each other no server is managing them.

Advantages:

i.) High Performance

ii.) Failure of single node doesn’t fails whole network.

iii.) Easily scalable and robustness.

Disadvantages:

i.) We cannot administrate the network.

ii.) Cannot filter the network traffic that what files are

being shared.

iii.) Locating peers and offering services is a

challenging tasks.

Example:

Gnutella 0.

 Centralized P2P Model:

In this model which there is a central server whose job is that

it is maintaining all the records of files which each node have.

When a node needs a file its requests to the server makes

the lookup in its database and redirects the requesting node

to that node which has file.

So then this requesting node makes the direct connection

with that node which has file.

Note Server only searches file it doesnot transfer files.

For transfering of files nodes make direct connection

With each other.

Continued….

Hybird P2P Model:



Main advantage of Centralized model is faster and reliable resource

sharing.But there limitation is that scalabiilty of system is affected

by use of servers.



Main advantage of Decentralized model is that they take less

time in locating the resource as compared to the Centralized

Model.



Hybird Model is a type of Model which is introduced to take

advantage of both centralized and decentralized system this

model doesn’t uses the server hence scalability issue got

resolved.



This model introduced the new concept of SUPERNODES.Hybird

model uses Super nodes,they are the more powerful nodes then

the other nodes they are dynamically choosen.By use of super

nodes Resource locating become faster. By using supernodes we

can take advantage of both decentralized search techniques and

centralized search techniques.



Continued….

Continued….



Advantages of Hybird Model:

I.) Issue of scalability in centralized

model resolved.

ii.) We can fastly locate the resource by use of

supernodes.



Disadvantages:

i.) Searching is still based upon the flooding.

ii.) Loss of Distribution , more centralized

control.

Example:

Gnutella v0.

Continued….



Skype used TCP for signalling and both

UDP and TCP for data transferring.



All users communication are encrypted

using AES 256-bit.



Normal Login:

i.) Skype client connects with the

supernode. ii.) Skype client is authenticated

using skype login server.

Some important terminologies:

 Seeder: Seeder is a one whose file is completely downloaded but its

uploading.

 Leecher: Some one who is downloading file.

 Peer: Collective term for seeder and leecher.

 Swarm : A group of peers sending or receiving simultaneously the same

file.

 Torrent file: A file contains information(Address/hostname) about

Tracker.

 Tracker : A server that manages the bit torrent transfer process. tracker

is computer which acts as a server, and maintains a list of nodes which are

participating in the system (ie. computers that are currently downloading or

uploading file data). For a new node to join a Bittorrent network, it sends a

message to the tracker requesting the IPs of some of the other participating

nodes, so that it can connect to them and begin downloading. No actual file

data is downloaded from the tracker; its job is simply to facilitate node

discovery.

Overall

Architecture

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker Web Server

Overall

Architecture

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker Web Server

Overall

Architecture

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker Web Server

Overall

Architecture

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker Web Server