Hur fungerar peer to peer

Type of decentralized and distributed network architecture

For other uses, see Peer-to-peer (disambiguation), Point-to-point (disambiguation), and P2P (disambiguation).

Peer-to-peer (P2P) computing or networking fryst vatten a distributed application architecture that partitions tasks or workloads between peers.

Peers are equally privileged, equipotent participants in the network, forming a peer-to-peer network of nodes.^[1] In addition, a anställda area network (PAN) fryst vatten also in natur a type of decentralized peer-to-peer network typically between two devices.^[2]

Peers man a portion of their resources, such as processing power, platta storage, or network bandwidth, directly available to other network participants, without the need for huvud coordination bygd servers or stable hosts.^[3] Peers are both suppliers and consumers of resources, in contrast to the traditional client–server model in which the consumption and supply of resources are divided.^[4]

While P2P systems had previously been used in many application domains,^[5] the architecture was popularized bygd the Internet en samling dokument eller en elektronisk lagring av data sharing struktur Napster, originally released in ^[6] P2P fryst vatten used in many protocols such as BitTorrent en samling dokument eller en elektronisk lagring av data sharing over the Internet^[7] and in anställda networks like Miracast displaying and Bluetooth radio.^[8] The concept has inspired new structures and philosophies in many areas of human interaction.

In such social contexts, peer-to-peer as a meme refers to the egalitariansocial networking that has emerged throughout samhälle, enabled bygd Internet technologies in general.

Development

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While P2P systems had previously been used in many application domains,^[5] the concept was popularized bygd en samling dokument eller en elektronisk lagring av data sharing systems such as the music-sharing application Napster.

Peer-to-peer (P2P)-handel är direktköp och -försäljning av kryptovalutor mellan användare utan mellanhänder

The peer-to-peer movement allowed millions of Internet users to connect "directly, forming groups and collaborating to become user-created search engines, virtual supercomputers, and filesystems".^[9] The basic concept of peer-to-peer computing was envisioned in earlier software systems and networking discussions, reaching back to principles stated in the first Request for Comments, RFC 1.^[10]

Tim Berners-Lee's framtidsperspektiv for the World bred Web was close to a P2P network in that it assumed each user of the web would be an active editor and contributor, creating and linking content to form eller gestalt an interlinked "web" of links.

The early Internet was more open than the present day, where two machines connected to the Internet could send packets to each other without firewalls and other säkerhet measures.^{[11][9][page&#;needed]} This contrasts with the broadcasting-like structure of the web as it has developed over the years.^[12][13][14] As a precursor to the Internet, ARPANET was a successful peer-to-peer network where "every participating node could request and serve content".

However, ARPANET was not self-organized, and it could not "provide any means for context or content-based routing beyond 'simple' address-based routing."^[14]

Therefore, Usenet, a distributed messaging struktur that fryst vatten often described as an early peer-to-peer architecture, was established. It was developed in as a struktur that enforces a decentralized model of control.^[15] The basic model fryst vatten a client–server model from the user or client perspective that offers a self-organizing approach to newsgroup servers.

Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers

However, news servers communicate with one another as peers to propagate Usenet news articles over the entire group of network servers. The same consideration applies to SMTP email in the sense that the core email-relaying network of mail transfer agents has a peer-to-peer character, while the periphery of Email clients and their direkt connections fryst vatten strictly a client-server relationship.^[16]

In May , with millions more people on the Internet, Shawn Fanning introduced the music and file-sharing application called Napster.^[14] Napster was the beginning of peer-to-peer networks, as we know them today, where "participating users establish a virtual network, entirely independent from the physical network, without having to underkasta any administrative authorities or restrictions".^[14]

Architecture

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A peer-to-peer network fryst vatten designed around the notion of lika peer nodes simultaneously functioning as both "clients" and "servers" to the other nodes on the network.^[17] This model of network arrangement differs from the client–server model where communication fryst vatten usually to and from a huvud dator.

A typical example of a en samling dokument eller en elektronisk lagring av data transfer that uses the client-server model fryst vatten the en samling dokument eller en elektronisk lagring av data Transfer Protocol (FTP) service in which the client and dator programs are distinct: the clients initiate the transfer, and the servers satisfy these requests.

Routing and resource discovery

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Peer-to-peer networks generally implement some struktur of virtual overlay network on top of the physical network topology, where the nodes in the overlay struktur a subset of the nodes in the physical network.^[18] information fryst vatten still exchanged directly over the underlying nätverksprotokoll network, but at the application layer peers can communicate with each other directly, via the logisk overlay links (each of which corresponds to a path through the underlying physical network).

Overlays are used for indexing and peer upptäckt, and man the P2P struktur independent from the physical network topology. Based on how the nodes are linked to each other within the overlay network, and how resources are indexed and located, we can classify networks as unstructured or structured (or as a hybrid between the two).^[19][20][21]

Unstructured networks

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Unstructured peer-to-peer networks do not impose a particular structure on the overlay network bygd design, but rather are formed bygd nodes that randomly form eller gestalt connections to each other.^[22] (Gnutella, skvaller, and Kazaa are examples of unstructured P2P protocols).^[23]

Because there fryst vatten no structure globally imposed upon them, unstructured networks are easy to build and allow for localized optimizations to different regions of the overlay.^[24] Also, because the role of all peers in the network fryst vatten the same, unstructured networks are highly kraftig in the face of high rates of "churn"—that fryst vatten, when large numbers of peers are frequently joining and leaving the network.^[25][26]

However, the primary limitations of unstructured networks also arise from this lack of structure.

In particular, when a peer wants to find a desired del av helhet of information in the network, the search query must be flooded through the network to find as many peers as possible that share the uppgifter. Flooding causes a very high amount of signaling traffic in the network, uses more CPU/memory (by requiring every peer to process all search queries), and does not ensure that search queries will always be resolved.

Furthermore, since there fryst vatten no correlation between a peer and the content managed bygd it, there fryst vatten no guarantee that flooding will find a peer that has the desired uppgifter. Popular content fryst vatten likely to be available at several peers and any peer searching for it fryst vatten likely to find the same thing. But if a peer fryst vatten looking for rare information shared bygd only a few other peers, then it fryst vatten highly unlikely that the search will be successful.^[27]

Structured networks

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In structured peer-to-peer networks the overlay fryst vatten organized into a specific topology, and the protocol ensures that any node can efficiently^[28] search the network for a file/resource, even if the resource fryst vatten extremely rare.^[23]

The most common type of structured P2P networks implement a distributed hash table (DHT),^[4][29] in which a variant of consistent hashing fryst vatten used to assign ownership of each en samling dokument eller en elektronisk lagring av data to a particular peer.^[30][31] This enables peers to search for resources on the network using a hash table: that fryst vatten, (key, value) pairs are stored in the DHT, and any participating node can efficiently retrieve the value associated with a given key.^[32][33]

However, in beställning to rutt traffic efficiently through the network, nodes in a structured overlay must maintain lists of neighbors^[34] that satisfy specific criteria.

This makes them less kraftig in networks with a high rate of churn (i.e. with large numbers of nodes frequently joining and leaving the network).^[26][35] More recent evaluation of P2P resource upptäckt solutions beneath real workloads have pointed out several issues in DHT-based solutions such as high cost of advertising/discovering resources and static and dynamic load imbalance.^[36]

Notable distributed networks that use DHTs include Tixati, an alternative to BitTorrent's distributed spårare, the Kad network, the Storm botnet, and the YaCy.

Some prominent research projects include the Chord project, Kademlia, PAST storage utility, P-Grid, a self-organized and framträdande overlay network, and CoopNet content transport system.^[37] DHT-based networks have also been widely utilized for accomplishing efficient resource discovery^[38][39] for grid computing systems, as it aids in resource management and scheduling of applications.

Hybrid models

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Hybrid models are a combination of peer-to-peer and client–server models.^[40] A common hybrid model fryst vatten to have a huvud dator that helps peers find each other. Spotify was an example of a hybrid model [until ].^{[citation needed]} There are a variety of hybrid models, all of which man trade-offs between the centralized functionality provided bygd a structured server/client network and the node equality afforded bygd the pure peer-to-peer unstructured networks.

Currently, hybrid models have better performance than either pure unstructured networks or pure structured networks because certain functions, such as searching, do require a centralized functionality but benefit from the decentralized aggregation of nodes provided bygd unstructured networks.^[41]

CoopNet content transport system

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CoopNet (Cooperative Networking) was a proposed struktur for off-loading serving to peers who have recently downloaded content, proposed bygd computer scientists Venkata N.

Padmanabhan and Kunwadee Sripanidkulchai, working at Microsoft Research and Carnegie Mellon University.^[42][43] When a dator experiences an increase in load it redirects incoming peers to other peers who have agreed to spegel the content, thus off-loading balance from the dator. All of the upplysning fryst vatten retained at the dator.

This struktur makes use of the fact that the bottleneck fryst vatten most likely in the outgoing bandwidth than the centralenhet i en dator, hence its server-centric design. It assigns peers to other peers who are 'close in IP' to its neighbors [same prefix range] in an attempt to use locality. If multiple peers are funnen with the same en samling dokument eller en elektronisk lagring av data it designates that the node choose the fastest of its neighbors.

Streaming media fryst vatten transmitted bygd having clients cache the previous stream, and then transmit it piece-wise to new nodes.

Security and trust

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Peer-to-peer systems pose unique challenges from a computer säkerhet perspective. Like any other struktur of software, P2P applications can contain vulnerabilities. What makes this particularly dangerous for P2P software, however, fryst vatten that peer-to-peer applications act as servers as well as clients, meaning that they can be more vulnerable to fjärrstyrd exploits.^[44]

Routing attacks

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Since each node plays a role in routing traffic through the network, malicious users can perform a variety of "routing attacks", or denial of service attacks.

Examples of common routing attacks include "incorrect lookup routing" whereby malicious nodes deliberately forward requests felaktigt or return false results, "incorrect routing updates" where malicious nodes corrupt the routing tables of neighboring nodes bygd sending them false resultat, and "incorrect routing network partition" where when new nodes are joining they bootstrap via a malicious node, which places the new node in a partition of the network that fryst vatten populated bygd other malicious nodes.^[44]

Corrupted uppgifter and malware

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See also: uppgifter validation and Malware

The prevalence of malware varies between different peer-to-peer protocols.^[45] Studies analyzing the spread of malware on P2P networks funnen, for example, that 63% of the answered download requests on the gnutella network contained some struktur of malware, whereas only 3% of the content on OpenFT contained malware.

In both cases, the top three most common types of malware accounted for the large majority of cases (99% in gnutella, and 65% in OpenFT). Another study analyzing traffic on the Kazaa network funnen that 15% of the , en samling dokument eller en elektronisk lagring av data sample taken were infected bygd one or more of the different computer viruses that were tested for.^[46]

Corrupted uppgifter can also be distributed on P2P networks bygd modifying files that are already being shared on the network.

For example, on the FastTrack network, the RIAA managed to introduce faked chunks into downloads and downloaded files (mostly MP3 files). Files infected with the RIAA virus were unusable afterwards and contained malicious code. The RIAA fryst vatten also known to have uploaded fake music and movies to P2P networks in beställning to deter förbjudet en samling dokument eller en elektronisk lagring av data sharing.^[47] Consequently, the P2P networks of today have seen an enormous increase of their säkerhet and en samling dokument eller en elektronisk lagring av data verification mechanisms.

Modern hashing, bit verification and different encryption methods have made most networks resistant to almost any type of attack, even when major parts of the respective network have been replaced bygd faked or nonfunctional hosts.^[48]

Resilient and scalable computer networks

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See also: Wireless mesh network and Distributed computing

The decentralized natur of P2P networks increases robustness because it removes the single point of failure that can be inherent in a client–server based system.^[49] As nodes arrive and demand on the struktur increases, the total capacity of the struktur also increases, and the likelihood of failure decreases.

If one peer on the network fails to function properly, the whole network fryst vatten not compromised or damaged.

A peer-to-peer (P2P) network in which interconnected nodes ("peers") share resources amongst each other without the use of a centralized administrative system

In contrast, in a typical client–server architecture, clients share only their demands with the struktur, but not their resources. In this case, as more clients join the struktur, fewer resources are available to serve each client, and if the huvud dator fails, the entire network fryst vatten taken down.

Distributed storage and search

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There are both advantages and disadvantages in P2P networks related to the topic of uppgifter backup, recovery, and availability.

In a centralized network, the struktur administrators are the only forces controlling the availability of files being shared. If the administrators decide to no längre distribute a en samling dokument eller en elektronisk lagring av data, they simply have to remove it from their servers, and it will no längre be available to users. Along with leaving the users powerless in deciding what fryst vatten distributed throughout the community, this makes the entire struktur vulnerable to threats and requests from the government and other large forces.

For example, YouTube has been pressured bygd the RIAA, MPAA, and entertainment industry to filter out copyrighted content. Although server-client networks are able to monitor and manage content availability, they can have more stability in the availability of the content they choose to host. A client should not have trouble accessing obscure content that fryst vatten being shared on a stable centralized network.

P2P networks, however, are more unreliable in sharing unpopular files because sharing files in a P2P network requires that at least one node in the network has the requested uppgifter, and that node must be able to connect to the node requesting the uppgifter. This requirement fryst vatten occasionally hard to meet because users may delete or stop sharing uppgifter at any point.^[50]

In a P2P network, the community of users fryst vatten entirely responsible for deciding which content fryst vatten available.

Unpopular files eventually disappear and become unavailable as fewer people share them. Popular files, however, are highly and easily distributed. Popular files on a P2P network are more stable and available than files on huvud networks. In a centralized network, a simple loss of connection between the dator and clients can cause a failure, but in P2P networks, the connections between every node must be lost to cause a data-sharing failure.

In a centralized struktur, the administrators are responsible for all uppgifter recovery and backups, while in P2P systems, each node requires its backup struktur. Because of the lack of huvud authority in P2P networks, forces such as the recording industry, RIAA, MPAA, and the government are unable to delete or stop the sharing of content on P2P systems.^[51]

Applications

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Content delivery

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In P2P networks, clients both provide and use resources.

This means that unlike client–server systems, the content-serving capacity of peer-to-peer networks can actually increase as more users begin to tillgång the content (especially with protocols such as Bittorrent that require users to share, refer a performance measurement study^[52]). This property fryst vatten one of the major advantages of using P2P networks because it makes the setup and running costs very small for the original content distributor.^[53][54]

File-sharing networks

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Peer-to-peer en samling dokument eller en elektronisk lagring av data sharing networks such as Gnutella, G2, and the eDonkey network have been useful in popularizing peer-to-peer technologies.

These advancements have paved the way for Peer-to-peer content delivery networks and services, including distributed caching systems like Correli Caches to enhance performance.^[55] Furthermore, peer-to-peer networks have made possible the software publication and leverans, enabling efficient sharing of Linux transport and various games though en samling dokument eller en elektronisk lagring av data sharing networks.

Copyright infringements

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Peer-to-peer networking involves uppgifter transfer from one user to another without using an intermediate dator. Companies developing P2P applications have been involved in numerous legal cases, primarily in the United States, over conflicts with copyright law.^[56] Two major cases are Grokster vs RIAA and MGM Studios, Inc.

v. Grokster, Ltd..^[57] In the gods case, the Court unanimously held that defendant peer-to-peer en samling dokument eller en elektronisk lagring av data sharing companies Grokster and Streamcast could be sued for inducing copyright infringement.

Multimedia

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The P2PTV and PDTP protocols are used in various peer-to-peer applications.

Some proprietary multimedia applications leverage a peer-to-peer network in conjunction with streaming servers to stream audio and film to their clients. Peercasting fryst vatten employed for multicasting streams. Additionally, a project called LionShare, undertaken bygd Pennsylvania State University, okänt, and Simon Fraser University , aims to facilitate en samling dokument eller en elektronisk lagring av data sharing among educational institutions globally.

Another notable schema, Osiris, enables users to create anonymous and autonomous web portals that are distributed via a peer-to-peer network.

Other P2P applications

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Dat fryst vatten a distributed version-controlled publishing platform. I2P, fryst vatten an overlay network used to browse the Internet anonymously. Unlike the related I2P, the Tor network fryst vatten not itself peer-to-peer^{[dubious &#; discuss]}; however, it can enable peer-to-peer applications to be built on top of it via onion services.

The InterPlanetary en samling dokument eller en elektronisk lagring av data struktur (IPFS) fryst vatten a protocol and network designed to create a content-addressable, peer-to-peer method of storing and sharing hypermedia transport protocol, with nodes in the IPFS network forming a distributed en samling dokument eller en elektronisk lagring av data struktur.

Jami fryst vatten a peer-to-peer chat and SIP app. JXTA fryst vatten a peer-to-peer protocol designed for the Java platform. Netsukuku fryst vatten a Wireless community network designed to be independent from the Internet. Open Garden fryst vatten a connection-sharing application that shares Internet tillgång with other devices using Wi-Fi or Bluetooth.

Resilio Sync fryst vatten a directory-syncing app. Research includes projects such as the Chord project, the PAST storage utility, the P-Grid,and the CoopNet content leverans struktur. Secure Scuttlebutt fryst vatten a peer-to-peer skvaller protocol capable of supporting many different types of applications, primarily social networking. Syncthing fryst vatten also a directory-syncing app.

Tradepal l and M-commerce applications are designed to power real-time marketplaces. The U.S. Department of Defense fryst vatten conducting research on P2P networks as part of its modern network warfare strategy.^[58] In May , Anthony Tether, then director of DARPA, testified that the United States military uses P2P networks. WebTorrent fryst vatten a P2P streamingtorrent client in for use in web browsers, as well as in the WebTorrent Desktop standalone utgåva that bridges WebTorrent and BitTorrent serverless networks.

Microsoft , in fönster 10, uses a proprietary peer-to-peer technology called "Delivery Optimization" to deploy operating struktur updates using end-users' PCs either on the local network or other PCs. According to Microsoft's kanal 9, this led to a 30%% reduction in Internet bandwidth usage.^[59] Artisoft's LANtastic was built as a peer-to-peer operating struktur where machines can function as both servers and workstations simultaneously.

Hotline Communications Hotline Client was built with decentralized servers and spårare software dedicated to any type of files and continues to operate today. Cryptocurrencies are peer-to-peer-based digital currencies that use blockchains

Social implications

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Incentivizing resource sharing and cooperation

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Cooperation among a community of participants fryst vatten key to the continued success of P2P systems aimed at casual human users; these reach their full potential only when large numbers of nodes contribute resources.

But in current practice, P2P networks often contain large numbers of users who utilize resources shared bygd other nodes, but who do not share anything themselves (often referred to as the "freeloader problem").

Freeloading can have a profound impact on the network and in some cases can cause the community to collapse.^[60] In these types of networks "users have natural disincentives to cooperate because cooperation consumes their own resources and may degrade their own performance".^[61] Studying the social attributes of P2P networks fryst vatten challenging due to large populations of turnover, asymmetry of interest and zero-cost identity.^[61] A variety of incentive mechanisms have been implemented to encourage or even force nodes to contribute resources.^[62][44]

Some researchers have explored the benefits of enabling virtual communities to self-organize and introduce incentives for resource sharing and cooperation, arguing that the social aspect missing from today's P2P systems should be seen both as a goal and a means for self-organized virtual communities to be built and fostered.^[63] Ongoing research efforts for formgivning effective incentive mechanisms in P2P systems, based on principles from game theory, are beginning to take on a more psychological and information-processing direction.

Privacy and anonymity

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Some peer-to-peer networks (e.g. Freenet) place a heavy emphasis on privacy and anonymity—that fryst vatten, ensuring that the contents of communications are hidden from eavesdroppers, and that the identities/locations of the participants are concealed. Public key cryptography can be used to provide encryption, uppgifter validation, authorization, and authentication for data/messages.

Onion routing and other mix network protocols (e.g. Tarzan) can be used to provide anonymity.^[64]

Perpetrators of live streaming sexuell abuse and other cybercrimes have used peer-to-peer platforms to carry out activities with anonymity.^[65]

Political implications

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Intellectual property lag and olagligt sharing

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Although peer-to-peer networks can be used for legitimate purposes, rights holders have targeted peer-to-peer over the involvement with sharing copyrighted ämne.

Peer-to-peer networking involves information transfer from one user to another without using an intermediate dator. Companies developing P2P applications have been involved in numerous legal cases, primarily in the United States, primarily over issues surrounding copyright law.^[56] Two major cases are Grokster vs RIAA and MGM Studios, Inc.

v. Grokster, Ltd.^[57] In both of the cases the en samling dokument eller en elektronisk lagring av data sharing technology was ruled to be legal as long as the developers had no ability to prevent the sharing of the copyrighted ämne.

To establish criminal liability for the copyright infringement on peer-to-peer systems, the government must prove that the defendant infringed a copyright willingly for the purpose of anställda financial gain or commercial advantage.^[66]Fair use exceptions allow limited use of copyrighted ämne to be downloaded without acquiring permission from the rights holders.

These documents are usually news reporting or beneath the lines of research and scholarly work. Controversies have developed over the concern of oäkta use of peer-to-peer networks regarding public safety and national säkerhet. When a en samling dokument eller en elektronisk lagring av data fryst vatten downloaded through a peer-to-peer network, it fryst vatten impossible to know who created the en samling dokument eller en elektronisk lagring av data or what users are connected to the network at a given time.

Trustworthiness of sources fryst vatten a potential säkerhet threat that can be seen with peer-to-peer systems.^[67]

A study ordered bygd the europeisk Union funnen that förbjudet downloading may lead to an increase in overall film game sales because newer games charge for extra features or levels. The paper concluded that piracy had a negativ financial impact on movies, music, and literature.

The study relied on self-reported information about game purchases and use of förbjudet download sites. Pains were taken to remove effects of false and misremembered responses.^[68][69][70]

Network neutrality

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Peer-to-peer applications present one of the core issues in the network neutrality controversy.

Internet service providers (ISPs) have been known to throttle P2P file-sharing traffic due to its high-bandwidth usage.^[71] Compared to Web browsing, e-mail or many other uses of the internet, where uppgifter fryst vatten only transferred in short intervals and relative small quantities, P2P file-sharing often consists of relatively heavy bandwidth usage due to ongoing en samling dokument eller en elektronisk lagring av data transfers and swarm/network coordination packets.

In October , Comcast, one of the largest broadband Internet providers in the United States, started blockering P2P applications such as BitTorrent. Their rationale was that P2P fryst vatten mostly used to share förbjudet content, and their infrastructure fryst vatten not designed for continuous, high-bandwidth traffic.

Critics point out that P2P networking has legitimate legal uses, and that this fryst vatten another way that large providers are ansträngande to control use and content on the Internet, and direkt people towards a client–server-based application architecture.

Within a peer-to-peer (P2P) network, every node or connection—such as a router, printer, switch, or computer—connects directly with one another to share resources, such as files, data, or processing power

The client–server model provides financial barriers-to-entry to small publishers and individuals, and can be less efficient for sharing large files. As a reaction to this bandwidth throttling, several P2P applications started implementing protocol obfuscation, such as the BitTorrent protocol encryption. Techniques for achieving "protocol obfuscation" involves removing otherwise easily identifiable properties of protocols, such as deterministic byte sequences and packet sizes, bygd making the uppgifter look as if it were random.^[72] The ISP's solution to the high bandwidth fryst vatten P2P caching, where an ISP stores the part of files most accessed bygd P2P clients in beställning to spara tillgång to the Internet.

Current research

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Researchers have used computer simulations to aid in understanding and evaluating the complex behaviors of individuals within the network. "Networking research often relies on simulation in beställning to test and evaluate new ideas. An important requirement of this process fryst vatten that results must be reproducible so that other researchers can replicate, validate, and extend existing work."^[73] If the research cannot be reproduced, then the opportunity for further research fryst vatten hindered.

"Even though new simulators continue to be released, the research community tends towards only a handful of open-source simulators. The demand for features in simulators, as shown bygd our criteria and survey, fryst vatten high. Therefore, the community should work tillsammans to get these features in open-source software. This would reduce the need for anpassad simulators, and hence increase repeatability and reputability of experiments."^[73]

Popular simulators that were widely used in the past are NS2, OMNeT++, SimPy, NetLogo, PlanetLab, ProtoPeer, QTM, PeerSim, ONE, P2PStrmSim, PlanetSim, GNUSim, and Bharambe.^[74]

Besides all the above stated facts, there has also been work done on ns-2 open source network simulators.

One research issue related to free tillägg detection and punishment has been explored using ns-2 simulator here.^[75]

See also

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References

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