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Version 45.1 by Zenna Elfen on 2026/01/05 20:02
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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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21 {{box title=" **Contents**"}}
22 {{toc depth="5"/}}
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32 == Building Blocks of P4P Networks ==
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34 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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43 ==== **1. Data Synchronization** ====
44
45 > 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.
46
47 * //How do peers detect differences and synchronize state?//
48 * 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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50
51
52 ==== **2. Collaborative Data Structures & Conflict Resolution** ====
53
54 > 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.
55
56 * //How do peers collaboratively change shared data and merge conflicts?//
57 * Examples: CRDTs (Yjs, Automerge), OT, Event Sourcing, Stream Processing, Version Vectors, Peritext
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59
60
61 ==== **3. Data Storage & Replication** ====
62
63 > 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.
64
65 * //How is data persisted locally and replicated between peers?//
66 * Examples: SQLite, IndexedDB, LMDB, Hypercore (append-only logs), WALs, Merkle-DAGs (IPFS/IPLD), Blob/media storage
67
68
69
70 ==== **4. Peer & Content Discovery** ====
71
72 > Discovery occurs in two phases:
73 > 1. **Peer Discovery** → finding _any_ nodes
74 > 2. **Topic Discovery** → finding _relevant_ nodes or resources
75 > These mechanisms enable decentralized bootstrapping and interest-based overlays.
76
77 * //How do peers find each other, and how do they discover content in the network?//
78 * 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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80
81
82 ==== **5. Identity & Trust** ====
83
84 > Identity systems ensure reliable mapping between peers and cryptographic keys. They underpin authorization, federated trust, and secure overlays.
85
86 * //How peers identify themselves, authenticate, and establish trustworthy relationships?//
87 * Examples: PKI, Distributed Identities (DIDs), Web-of-Trust, TOFU (SSH-style), Verifiable Credentials (VCs), Peer key fingerprints (libp2p PeerIDs), Key transparency logs
88
89
90
91 ==== **6. Transport Layer** ====
92
93 > This layer provides logical connections and flow control. QUIC and WebRTC bring modern congestion control and encryption defaults; Interpeer explores transport beyond IP assumptions.
94
95 * //How do peers establish end-to-end byte streams and reliable delivery?//
96 * Examples: TCP, UDP, QUIC, SCTP, WebRTC DataChannels, Interpeer transport stack
97
98
99
100 ==== **7. Underlying Transport (Physical/Link Layer)** ====
101
102 > Highly relevant for **offline-first / edge networks**, device-to-device communication, and mesh networks and relates to the hardware which facilitates connections.
103
104 * //How does data move across the medium?//
105 * Examples: Ethernet, Wi-Fi Direct / Wi-Fi Aware (post-AWDL), Bluetooth Mesh, LoRa, NFC, Cellular, CSMA/CA, TDMA, FHSS
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107
108
109 ==== **8. Session & Connection Management** ====
110
111 > Manages **connection lifecycle**, including authentication handshakes, reconnection after drops, and session continuation—especially important in lossy or mobile networks.
112
113 * //How are connections initiated, authenticated, resumed, and kept alive?//
114 * Examples: TLS handshake semantics, Noise IK/XX patterns, session tokens, keep-alive heartbeats, reconnection strategies, session resumption tickets
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117
118 ==== **9. Content Addressing** ====
119
120 > Content addressing ensures **immutability, verifiability, and deduplication**. Identity of data = cryptographic hash, enabling offline-first and tamper-evident systems.
121
122 * //How is data addressed and verified by content, not location?//
123 * Examples: IPFS CIDs, BitTorrent infohashes, Git hashes, SHA-256 addressing, Named Data Networking (NDN)
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125
126
127 ==== **10. P2P Connectivity** ====
128
129 > Connectivity ensures peers bypass NATs/firewalls to reach each other. 
130
131 * //How can two peers connect directly across networks, firewalls, and NATs?//
132 * Examples: IPv6 direct, NAT Traversal, STUN, TURN, ICE (used in WebRTC), UDP hole punching, UPnP
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134
135
136 ==== **11. Session & Connection Management** ====
137
138 > Manages **connection lifecycle**, including authentication handshakes, reconnection after drops, and session continuation.
139
140 * //How are connections initiated, authenticated, resumed, and kept alive?//
141 * Examples: TLS handshake semantics, Noise IK/XX patterns, session tokens, keep-alive heartbeats, reconnection strategies, session resumption tickets
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143
144
145 ==== **12. Message Format & Serialization** ====
146
147 > Serialization ensures **portable data representation**, forward-compatible schemas, and efficient messaging. IPLD provides content-addressed structuring for P2P graph data.
148
149 * //How is data encoded, structured, and made interoperable between peers?//
150 * Examples: CBOR, Protocol Buffers, Cap’n Proto, JSON, ASN.1, IPLD schemas, Flatbuffers
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153
154 ==== **13. File / Blob Synchronization** ====
155
156 > 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.
157
158 //How are large objects transferred and deduplicated efficiently across peers?//
159 Examples: BitTorrent chunking, IPFS block-store, NDN segments, rsync-style delta sync, ZFS send-receive, streaming blob transfers
160
161
162 ==== **14. Local Storage & Processing Primitives** ====
163
164 > Provides durable on-device state and local computation (event sourcing, materialization, compaction). Enables offline-first writes and deterministic replay.
165
166 * //How do nodes persist, index, and process data locally—without external servers?//
167 * 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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169
170
171 ==== **15. Crash Resilience & Abortability** ====
172
173 > 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.
174
175 * //How do nodes recover and maintain correctness under failure?//
176 * Examples: WALs, idempotent ops, partial log replay, transactional journaling, write fences
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180
181 == Distributed Network Types ==
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184 [[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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187
188 == Overview of P4P Networks ==
189
190 {{include reference="Projects.WebHome"/}}
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