BEGINNER_DOC_013 // BEGINNERS / NETWORK
NETWORK
Bitcoin runs on a peer-to-peer-p2p/">peer-to-peer network — thousands of nodes spread across
the world, each holding a full copy of the blockchain and enforcing the same rules. There is
no central server. No company owns the network. Any node that breaks the rules is simply
ignored. Consensus emerges from the nodes agreeing independently on the
same valid chain.
PEER-TO-PEER_TOPOLOGY
TRADITIONAL CLIENT-SERVER (BANK)
User → Bank Server → Ledger
(single point of control, single point of failure)
VS
BITCOIN PEER-TO-PEER NETWORK
Node ←→ Node ←→ Node ←→ Node
↕ ↕ ↕ ↕
Node ←→ Node ←→ Node ←→ Node
Every node is equal. Each validates independently.
No center. No administrator. No off switch.
TRANSACTION_&_BLOCK_PROPAGATION
PROPAGATION
When you broadcast a transaction or a miner finds a new block, the data spreads through the
network using a gossip protocol — each node tells its peers, who tell their peers.
1. Your wallet sends the transaction to 1–8 connected peers
2. Each peer validates the tx (signatures, amounts, double-spend)
3. Valid tx is forwarded to their peers
4. Within seconds, thousands of nodes know about it
5. Miners include it in a candidate block
6. Block found → same gossip propagation → entire network synced
Block propagation time: ~1–2 seconds to reach 90% of nodes
Transaction propagation: ~1 second
NODE_TYPES
SOVEREIGN
Downloads and validates every block and transaction since the Genesis Block. Maintains the full utxo-set/">UTXO set. Trusts no one — verifies everything independently.
Storage: ~600 GB (full chain, 2024)
RAM: ~6 GB (UTXO set in memory)
Bandwidth: ~500 MB/day
Software: Bitcoin Core (reference implementation)
A full node is the most sovereign way to use Bitcoin.
You verify your own transactions — no third party required.
SPV Node / Light Client
LIGHTWEIGHT
Downloads only block headers (~60 MB), not full blocks. Verifies proof-of-work but trusts full nodes to provide transaction data. Used in mobile wallets.
Downloads: Block headers only (80 bytes × ~850,000 blocks = ~68 MB)
Verifies: Proof-of-work chain (not full tx validation)
Trusts: Full nodes for transaction data
Risk: Cannot detect invalid transactions without full node
SPV provides good security for everyday amounts. For large sums, running a full node is always recommended.
NETWORK_STATS
Reachable full nodes
~18,000 (2024)
Estimated total nodes
~50,000+ (inc. unreachable)
Default port
8333 (mainnet)
Max peer connections
125 outbound + inbound
Protocol version (2024)
70016
TERMINOLOGY_INDEX
P2P
Peer-to-peer. A network where all participants are equal — no central server or authority.
Full Node
A node that downloads, validates, and stores the complete blockchain. The strongest form of Bitcoin participation.
SPV
Simplified Payment Verification. A lightweight client that only checks block headers, not full transactions.
Mempool
Memory pool. Each node's local collection of unconfirmed transactions waiting to be mined.
Gossip Protocol
The method by which transactions and blocks spread — each node relays valid data to its peers.
Mainnet
The live Bitcoin network with real economic value. Distinguished from testnet (test coins only).