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Thursday, August 8, 2013

PPT On Peer to Peer Networks


Peer to Peer Networks Presentation Transcript:
1.Peer-to-peer networks

2.A peer-to-peer network, P2P, is consider any type of network architecture composed of contributors that make a part of their resources available to other contributors on the same network without the need for a server

3.Unstructured p2p networkIn 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 in order 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.

4.Structured P2P networks overcome the limitations of unstructured networks by maintaining a Distributed Hash Table (DHT).
whenever a peer wants to search for some data, it uses the global protocol to determine the peer(s) responsible for the data and then directs the search towards the responsible peer(s).

5.Classification of unstructured p2p
P2P networks can be roughly classified into two types — “pure P2P networks”, and “hybrid P2P networks”
A pure p2p system is a distributed system without any centralized control. All participating peers are equal, and each peer plays both the role of client and of server. Gnutella and Freenet  are examples of a pure P2P network.
There are two kinds of hybrid systems: centralized indexing and decentralized indexing.

6.In centralized indexing a central server maintains an index of the data or ?les that are currently being shared by active peers.
In decentralized indexing, some of the nodes assume a more important role than the rest of nodes. They are called ” SuperNodes”. Queries are sent to supernodes, not to other peers.

7.Famous p2p networks

It was used primarily for file sharing
 hybrid p2p network
Ways of action:
Client sends server the query, server responds to client
Client gets list of clients from server
All Clients send ID?s of the data they hold to the server and when client asks for data, server responds with specific addresses
peer downloads directly from other peer(s)

9.Napster subscribers also receive access to more than fifty commercial-free radio stations. Users can pause, play, fast-forward and rewind the radio stations at any time.

10.Advantages and drawbacks
Efficient search
Limited bandwidth usage
No per-node state
Central point of failure
Limited scale

Gnutella is a file sharing protocol.
When a user wishes to find a file, the user issues a query for the file to the Gnutella users about which it knows. Those users may or may not respond with results, and will forward the query request to any other Gnutella nodes they know about.
A query contains a Time-To-Live (TTL) field and will be forwarded until the TTL has been reached.

12.Advantages and drawbacks
Fault tolerant
No single point of failure
High bandwidth usage
Long time to locate item
No guarantee on success rate

Freenet represents the purest form of P2P system.
The primary mission of Freenet is to make use of the system anonymous.
Each file in the Freenet system is identified by a key. These are typically generated using the hash function. Typically a user starts by providing a short text description of the file. This description is then hashed to generate a key pair.

14.Freenet is able to optimize searches by creating routing tables. When a file is successfully located by a search, the file's key is inserted into a local routing table.
When a search is received by a node that contains the desired file, it returns the entire file as a successful result.

15.Advantages and drawbacks
complete decentralization
fault tolerance
scalability (to some degree)
questionable efficiency & performance
rare keys disappear from the system

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