Some Novel Approaches to Improve Performance of Peer - to - Peer systems

I feel very privileged to express my deepest and most sincere gratitude to my supervisor Dr.Diganta Goswami for invaluable suggestions and guidance during the development of the thesis, without which this work would not have materialized. An organized network architecture for unstructured p2p systems is developed where nodes are added to the network in a systematic manner to efficiently utilize node resources.

Introduction

Defining Peer­to­Peer

Peer-to-Peer has emerged as a new paradigm for communication on the Internet that can solve some of these problems. Peer-to-peer systems can be characterized as distributed systems where all nodes have identical capabilities and responsibilities and all communication is symmetric [RD01a].

Overlay System

For example, peers may change adjacencies and their overlapping neighbors due to membership changes. Maintaining connectivity and a consistent view of G across all nodes is the job of overlay maintenance.

Figure 1.1: Illustrating overlay and underlay

Distributed Hash Table

Also, the removal or dedicated elimination of a node should not have significant effects on the functionality of a DHT. The set primitive takes a value pair and stores it in the node responsible for the identifying key.

Motivation and Objectives

• Major Objectives of Our Work

In this technique, the free riders reappear with a different identity to get rid of the punishment imposed by the network. Placing the nodes in different hierarchies according to their performance, availability and reachability characteristics can help improve the overall performance of the system.

Organization of the Thesis

In section 2.1, a classification of p2p systems is presented based on a taxonomy of overlapping networks which was adopted based on the literature review. BAH+06] discuss data management in p2p systems with reference to data locality, query processing, data integration, and data consistency.

Classification of Peer­to­Peer Systems

• Unstructured Deterministic Systems
• Unstructured Non­deterministic Systems
• Structured DHT­based Systems
• Structured Non­DHT­based Systems
• Hybrid Systems
• Hierarchical Systems

The ith entry in the finger table for node P contains the identifier of the node which exceeds P's identifier by 2i−1. An entry in the proximity list contains the IP and ID of the neighboring node.

Figure 2.1: Illustrating Napster architecture

Summary

The purpose of this chapter is to develop a structured hierarchical overlay protocol (SHP) to improve the overall performance of the system. It is detrimental to the performance of the system if all the nodes are considered identical.

Table 2.3: Comparison of Hierarchical P2P protocols

Node Classification

Stable node: A temporary node becomes a stable node or peer after satisfying the stability period Tavg as shown in Figure 3.1. Therefore, this can be used to control the number of fully stable nodes in the system.

Figure 3.1: Categorization of nodes.

System Architecture

• Bootstrapping

The number of fully stable nodes in a group can be increased up to Gmax, where Gmax. When the number of nodes in a group becomes larger than Gmax, the group is divided into two groups, and one of the stable nodes is selected as a fully stable node.

Figure 3.2: Illustrating High-level architecture of SHP

Joining and Leaving of Nodes

• Effect of Temporary Node
• Effect of Stable Node
• Effect of Fully­stable Node

Joining/leaving a stable node in a group takes O((log(ns+nf))2) updates to repair the routing table as opposed to O((log(nt+ns+nf)))2) in the Chord protocol where nt, ns and nf are the number of temporary, stable and fully stable nodes in the group. Thus, the number of updates required during the joining of a fully stable node is O(Nf), where Nf is the total number of fully stable nodes in the system.

Query Processing

• Range Query
• Point Query

If the query does not fit into the interval maintained by the cluster, it is forwarded to one of the fully stable nodes of that cluster which in turn forwards it to the respective cluster, where a desired data space is available. For the range [X2−q], the message is sent to the fully stable node of the cluster to locate the desired cluster.

Table 3.3: A GRT showing key space AAA − DDD

Load Balancing

• Grading of Nodes
• Cost of Load Balancing

This requires O(1) lookup step, since each fully stable node knows about the fully stable nodes of other clusters. Each fully stable node periodically collects the load of the stable nodes in its group and classifies them based on the following load definition. If node P cannot find any lightly loaded nodes, then it sends a "NEED-NODE" request message to the fully stable cluster node.

Storage Requirement

NajSRshpandT SRshpare node storage request and shared storage request in SHP, and SRccp and T SRccp are node storage request and shared storage request in normal Chord protocol. The storage requirement for all fully stable nodes and stable nodes is obtained as follows. Therefore, T SRshp and T SRccp apply to compare SHP and CCP storage requirements.

Experimental Results

• Simulator
• Joining and Leaving of Nodes
• Query Processing
• Load Balance
• Storage Requirement

Related Works

In this approach, a routing table maintained for each node is not necessary because temporary nodes do not share anything and do not stay in the system for a long time. Each node aggregates load information from its neighbors and moves virtual servers from heavily loaded nodes to lightly loaded nodes. Although this is a simple method for load balancing, it is not efficient due to high communication overhead.

Summary

The churn rate is defined as the ratio of the number of participants who stop using a service to the average number of total participants for any given time period. The churn rate provides insight into the growth or decline of the user base, as well as the average length of service participation. A modification of the Chord protocol is presented to handle the inhibition rate, which in turn improves the efficiency of the system.

Node Classification

Fully stable nodes: A quasi-stable node becomes a fully stable node once all data in the finger table is updated.

The Protocol

• Node Joining
• Performance Analysis

In this approach, upgrading a temporary node to a virtual stable node requires O(logn) messages in the first step. A node p joins the network by contacting any existing fully stable node p� and asking p� to find a successor to p in the ring. Therefore, after the login steps, the node becomes a fully stable node and acts as a normal node in Chord.

Figure 4.2: Illustration of Temporal approach

Experimental Results

• Simulation Environment
• Observations

The number of messages for "Node connections in TCP" is calculated as the sum of messages required for "Boot-strapping Nodes" and "Upgrading Nodes in TCP". It is noted that performing the same number of connections in TCP and CCP requires different amount of messages. The number of messages required to leave a node may differ in TCP and CCP.

Table 4.2: Percentage of different file types shared in p2p system

Related Works

Here, while preserving O(logn) routing latency, the routing is aimed at reducing the cost of each hop.

Summary

If a neighbor receiving the request is unable to provide the requested resource, it forwards the query to all its neighbors except the querying node. We first define different terms used in the subsequent sections in section 5.1 and give the system architecture in section 5.2. Experimental results are discussed in section 5.4 and section 5.5 discusses the related works for this chapter.

Terminologies Used

This network architecture is characterized by O(logmn) network diameter and O(logmn) messages for node joining and node failure, where is the number of nodes in the network and m is the maximum number of children of a node. CHAPTER 5� UNSTR� HIERARCHICAL OVERLAY PROTOCOL 108. that of Q and is more stable than Q. The stability of a node is defined by the time it is in the p2p network. Token flow in the network controls the network growth and ensures hierarchy of nodes in the system.

HUP Structure

• Bootstrapping

A node that wants to join a network searches for already connected nodes in the network. Each node in the system has information from at least one of the super nodes. The identity, share size, and timestamp of a node in the network are maintained in the above table.

Figure 5.1: Illustration of High-level Architecture of HUP

Algorithms

• Node Joining
• Query Processing
• Edge Congestion

Step 5: Otherwise, the query is forwarded to the left node, right node and parent node. Step 4: If S is a supernode, then the query is forwarded to the left child node of S. In HUP, each node initially forwards the query Q to the upper levels of the network.

Figure 5.4: Routing in Gnutella for degree 3, label indicates TTL value.

Experimental Results

• Node Joining
• Query Processing

Related work

They introduce metadata files and construct a hierarchical architecture based on different contents of shared resources. CCF04] describe a super-peer-based framework in which the peers are organized according to their responsibilities. In our approach to HUP, a hierarchical overlay network structure is designed based on the shared size and stability of nodes.

Figure 5.10: Query Success Rate vs T T L for network size 100, 500 and 1000

Summary

Free riders create many problems in the network, such as it can drop queries made by others. Similarly, a launderer is like a free runner who frequently leaves the system and reappears with a different identity to get rid of fines imposed by the network. Peer-to-peer network system is based on the contribution made by the peers present in the network.

System Model

• Bootstrapping
• Registration Service
• Avoiding Free Riders
• Stabilization

Fully stable nodes are used for communication between clusters at the first level of the hierarchy. A fully stable node upgrades these recommended normal nodes to stable nodes based on certain criteria. When a fully stable node wants to leave the network, it upgrades one of the level 2 stable nodes (which is connected to it) to a fully stable node.

Figure 6.1: A high level architecture of hybrid p2p network

Query Processing

• Malicious Behavior of Nodes
• Load Balancing

Step 1: The stable node sends a query request with index X to all neighboring stable nodes in its cluster. The fully stable node executes Algorithm 3 and returns the corresponding node list to the stable nodeSNij. Step 2: The fully stable node sends a query request with indexX to all fully stable nodes in the system.

Experiment Results

• Event­Grade Analysis
• Event­Query Analysis
• Malicious Behavior of Nodes
• Grade Value Analysis
• Load Balancing

The new node's score values ​​are updated based on the number of resources added. The score value of the inquirer node is decreased and the score value of the responder node is increased. It is observed that some nodes in the system can be upgraded to a higher level depending on the needs of the system.

Table 6.1: Number of nodes having Grade-0, Grade-1 and Grade-2 during each multiples of 1000 iterations

Related Works

BAS03] use game theory to study peer behavior and propose an incentive scheme based on differential services to eliminate free riding in the p2p system. KKU04] propose a measurement-based approach to reduce free-riding in unstructured p2p system; their scheme requires each peer to monitor their neighboring peers to control free-riding. In our system, we have proposed a 3-layer hierarchy to handle issues such as efficient search, network management, free-riding elimination, and.

Table 6.4: Changing of grading with reference to P $ spent

Summary

In this work, we have made an attempt to improve the efficiency of p2p systems by proposing different mechanisms considering different aspects of structured and unstructured systems. Existing p2p systems are completely flat in which all participating peers take an equal role in the network. In this context, we are inspired to classify nodes based on different parameters and place them in different hierarchy levels.

Major Contributions

With nodes in the system and T T Loflog2n, the query success rate in HU P is at least 50%. It introduces better incentive mechanisms with an efficient ranking system of nodes at different hierarchies. All these methods were simulated using appropriate tools developed in the context and experimental results were used to substantiate our claims made in each case.

Future Works

In Proceedings of the 3rd International Conference on Peer-to-Peer Computing, pages 48–56, Washington, DC, USA, 2003. In Proceedings of the 5th International IEEE Conference on Peer-to-Peer Computing, pages. In Proceedings of the First IEEE International Conference on Peer-to-Peer Computing, pages 99–100, Linkoping, Sweden, August 2001.