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Version 34.1 by Zenna Elfen on 2026/01/05 19:50
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5 = Peer-for-Peer Networks =
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7 P4P, short for Peer-4-Peer (which in turn is short for Peer-for-Peer) are a family of networks which build on principles of local-first, peer-2-peer, open-source, routing agnostic (offline-first) and mutual-aid principles. The above is a lot of terms which in and of themselves carry a lot of meaning, yet when combined they enable censorship-resistant, resilient and adaptive, sustainable and energy-efficient communication infrastructures.
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15 == Building Blocks of P4P Networks ==
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20 To fully assemble a P4P network one needs a few different building blocks, below is an overview of 15 of those building blocks. Lost in translation? Take a look at the [[terminology>>doc:P4P.Definitions.WebHome]].
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30 {{box title="==== Contents ====
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32 ====== ======"}}
33 {{toc depth="5"/}}
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45 ==== **1. Data Synchronization** ====
46
47 > Synchronization answers **how updates flow between peers** and how they determine what data to exchange. This layer is about **diffing, reconciliation, order, causality tracking, and efficient exchange**, not persistence or user-facing collaboration semantics.
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49 * //How do peers detect differences and synchronize state?//
50 * Examples: Range-Based Set Reconciliation, RIBLT, Gossip-based sync, State-based vs op-based sync, Lamport/Vector/HLC clocks, Braid Protocol
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54 ==== **2. Collaborative Data Structures & Conflict Resolution** ====
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56 > This layer defines **how shared data evolves** when multiple peers edit concurrently. It focuses on **conflict-free merging, causality, and consistency of meaning**, not transport or storage. CRDTs ensure deterministic convergence, while event-sourced or stream-driven models maintain a history of all changes and derive consistent state from it.
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58 * //How do peers collaboratively change shared data and merge conflicts?//
59 * Examples: CRDTs (Yjs, Automerge), OT, Event Sourcing, Stream Processing, Version Vectors, Peritext
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63 ==== **3. Data Storage & Replication** ====
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65 > This layer focuses on **durability, consistency, and redundancy**. It handles write-paths, crash-resilience, and replication semantics across nodes. It is the “database/storage engine” layer where **data lives and survives over time**, independent of sync or merging logic.
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67 * //How is data persisted locally and replicated between peers?//
68 * Examples: SQLite, IndexedDB, LMDB, Hypercore (append-only logs), WALs, Merkle-DAGs (IPFS/IPLD), Blob/media storage
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71
72 ==== **4. Peer & Content Discovery** ====
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74 > Discovery occurs in two phases:
75 > 1. **Peer Discovery** → finding _any_ nodes
76 > 2. **Topic Discovery** → finding _relevant_ nodes or resources
77 > These mechanisms enable decentralized bootstrapping and interest-based overlays.
78
79 * //How do peers find each other, and how do they discover content in the network?//
80 * Examples: DHTs (Kademlia, Pastry), mDNS, DNS-SD, Bluetooth scanning, QR bootstrapping, static peer lists, Interest-based routing, PubSub discovery (libp2p), Rendezvous protocols
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84 ==== **5. Identity & Trust** ====
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86 > Identity systems ensure reliable mapping between peers and cryptographic keys. They underpin authorization, federated trust, and secure overlays.
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88 * //How peers identify themselves, authenticate, and establish trustworthy relationships?//
89 * Examples: PKI, Distributed Identities (DIDs), Web-of-Trust, TOFU (SSH-style), Verifiable Credentials (VCs), Peer key fingerprints (libp2p PeerIDs), Key transparency logs
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93 ==== **6. Transport Layer** ====
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95 > This layer provides logical connections and flow control. QUIC and WebRTC bring modern congestion control and encryption defaults; Interpeer explores transport beyond IP assumptions.
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97 * //How do peers establish end-to-end byte streams and reliable delivery?//
98 * Examples: TCP, UDP, QUIC, SCTP, WebRTC DataChannels, Interpeer transport stack
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101
102 ==== **7. Underlying Transport (Physical/Link Layer)** ====
103
104 > Highly relevant for **offline-first / edge networks**, device-to-device communication, and mesh networks and relates to the hardware which facilitates connections.
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106 * //How does data move across the medium?//
107 * Examples: Ethernet, Wi-Fi Direct / Wi-Fi Aware (post-AWDL), Bluetooth Mesh, LoRa, NFC, Cellular, CSMA/CA, TDMA, FHSS
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111 ==== **8. Session & Connection Management** ====
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113 > Manages **connection lifecycle**, including authentication handshakes, reconnection after drops, and session continuation—especially important in lossy or mobile networks.
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115 * //How are connections initiated, authenticated, resumed, and kept alive?//
116 * Examples: TLS handshake semantics, Noise IK/XX patterns, session tokens, keep-alive heartbeats, reconnection strategies, session resumption tickets
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119
120 ==== **9. Content Addressing** ====
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122 > Content addressing ensures **immutability, verifiability, and deduplication**. Identity of data = cryptographic hash, enabling offline-first and tamper-evident systems.
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124 * //How is data addressed and verified by content, not location?//
125 * Examples: IPFS CIDs, BitTorrent infohashes, Git hashes, SHA-256 addressing, Named Data Networking (NDN)
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129 ==== **10. P2P Connectivity** ====
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131 > Connectivity ensures peers bypass NATs/firewalls to reach each other. 
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133 * //How can two peers connect directly across networks, firewalls, and NATs?//
134 * Examples: IPv6 direct, NAT Traversal, STUN, TURN, ICE (used in WebRTC), UDP hole punching, UPnP
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137
138 ==== **11. Session & Connection Management** ====
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140 > Manages **connection lifecycle**, including authentication handshakes, reconnection after drops, and session continuation.
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142 * //How are connections initiated, authenticated, resumed, and kept alive?//
143 * Examples: TLS handshake semantics, Noise IK/XX patterns, session tokens, keep-alive heartbeats, reconnection strategies, session resumption tickets
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147 ==== **12. Message Format & Serialization** ====
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149 > Serialization ensures **portable data representation**, forward-compatible schemas, and efficient messaging. IPLD provides content-addressed structuring for P2P graph data.
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151 * //How is data encoded, structured, and made interoperable between peers?//
152 * Examples: CBOR, Protocol Buffers, Cap’n Proto, JSON, ASN.1, IPLD schemas, Flatbuffers
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156 ==== **13. File / Blob Synchronization** ====
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158 > Bulk data syncing has **different trade-offs** than small collaborative state (chunking, deduplication, partial transfer, resume logic). Critical for media and archival P2P use-cases.
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160 //How are large objects transferred and deduplicated efficiently across peers?//
161 Examples: BitTorrent chunking, IPFS block-store, NDN segments, rsync-style delta sync, ZFS send-receive, streaming blob transfers
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164 ==== **14. Local Storage & Processing Primitives** ====
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166 > Provides durable on-device state and local computation (event sourcing, materialization, compaction). Enables offline-first writes and deterministic replay.
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168 * //How do nodes persist, index, and process data locally—without external servers?//
169 * Examples: RocksDB, LevelDB, SQLite, LMDB, local WALs/append-only logs, embedded stream processors (NATS Core JetStream mode, Actyx-like edge runtimes), Kafka-like libraries
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173 ==== **15. Crash Resilience & Abortability** ====
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175 > Ensures P2P apps don’t corrupt state on crashes. Tied to **local storage & stream-processing**, and critical in offline-first and distributed update pipelines. Abortability is the updated term for Atomicity as part of the ACID abbreviation.
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177 * //How do nodes recover and maintain correctness under failure?//
178 * Examples: WALs, idempotent ops, partial log replay, transactional journaling, write fences
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183 == Distributed Network Types ==
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186 [[Flowchart depicting distributed network variants, under development. Building on work from Z. Elfen, 2024: ~[~[https:~~~~/~~~~/doi.org/10.17613/naj7d-6g984~>~>https://doi.org/10.17613/naj7d-6g984~]~]>>image:P4P_Typology.png||alt="Flowchart depicting typologies of distributed networks, such as Friend-2-Friend, Grassroots Networks, Federated Networks, Local-First, P2P and P4P Networks" data-xwiki-image-style-alignment="center" height="649" width="639"]]
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197 == Overview of P4P Networks ==
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199 {{include reference="Projects.WebHome"/}}
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