Peer to Peer Research survey

TingYang Chang

Intro. Of P2P

Computers of the system was known as peers which sharing data files with each other.

Build an extremely resource-rich system by aggregating the resources of large number of nodes (peers).

Characteristics of P2P

Each peer asks for resources while providing resources as reward for the system.

Peers may join and leave the system at any time.

Distributed resources contained in each nodes.

Decentralized system.

Advantages

Sharing storage spaces with whole system. Thus peers without large disk space would be able to access huge amount of data.

Peers can freely join or leave at any time. One or more powerful, expensive servers will

not be necessary.

Challenges

The scale of the network and the autonomy of nodes make it difficult to identify and distribute the resources that are available.

Some peers may be malicious. Queries and topologies Resource management Security

Queries and topologies

Implementing efficient techniques for search and retrieval of data will be the key challenge.

Best search techniques depend on the needs of the application. For those focused on availability like archival syst

em and web caches, DHTs will be well-suited.

Structured systems

Better search efficiency. Better accuracy Tightly control the data placement and topolo

gy Often constructed with DHTs (distributed has

h tables)

chord

SETS: search enhanced by Topic Segmentation

Key idea is to arrange participants in a topic-segmented topology

Queries probe only a small subset of sites where most of the matching documents reside

Topic centroid: a succinct description of topic segment

Short distance link and long distance link

YAPPERS

A search protocol that can be viewed as a hybrid of structured and unstructured systems

Keyspace of all the keys that need to be stored is partitioned into a small number of buckets

The “coloring” issue Immediate neighborhood within h hops Extended neighborhood within 2h+1 hops

Unstructured system

More flexible applications with rich queries Meant for a wide range of users from

autonomous organizations.

Unstructured system

The search techniques should be simple and practical enough to be easily incorporated into existing systems

Effective search techniques need to make provisions for the unreliable nature of peers.

All techniques should tune itself according to the current state of the system.

Designing issues

Possible design choices Neighbor selection Query routing Query evaluation Content replication

Current message routing protocols

Routing protocols used in practice like Gnutella are based on flooding.

Flooding depends on The availability of the data that can satisfy the

query The position of the peer in the overlay The overlay structure

Improvements of existing systems

Iterative deepening Under policy P= { a, b, c} ;waiting time W

Directed BFS A node maintains simple statistics on its neighbors Node sends queries to the subset of neighbors with more

possibility satisfy the query.

Local indices Nodes maintain an index over the data within r hops All nodes at depths not listed in the policy simply forward

the query

The routing indices

Compact summaries of the content that can be reached via a link.

The GUESS protocol

An under-construction specification Goal: peers directly probe each other rather

than relying on other peers to forward queries In what order should peers be probed How to detect and prevent selfish behavior

since it’s much easier now for peers to abuse the system for personal gain.

Resource management

Aggregating and allocating P2P resources Economic incentive to construct a resource

marketplace Data trading: both sites can make remote

copies of their collections

PeerDB

Security

P2P systems are highly susceptible to many forms of malicious attacks

Availability: the DoS (denial-of-service) attack Authenticity and trust: provide inauthentic file

s or bogus content

Conclusion

P2P system has recently become a very popular topic

This report is attempting to give an overview of ongoing research and developing techniques on currently P2P systems