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

Structured systems Better search efficiency. Better accuracy Tightly control the data placement and topology Often constructed with DHTs (distributed hash tables)

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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

Current message routing protocols Gnutella BFS with depth limit D Waste bandwidth and processing resources Freenet DFS with depth limit D Poor response time

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.

Role differentiation Super-peer networks differentiate between “super-peers” and “clients” Super-peers act as mini-index servers to number of clients

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 files 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