22. Network Layer
22.1 P2P Communication
The networking stack (quantos/src/network/) provides peer identity, discovery, gossip, synchronization and transport helpers. The concrete post-quantum KEM implementation is Kyber768-compatible (crypto/kyber_kem.rs), with a domain-separated handshake transcript and derived session key. The exact cipher, activation path, and coverage of every consensus message are deployment properties and must be verified from the active node configuration; the whitepaper does not claim universal ML-KEM-768 protection for all traffic.
22.2 Gossip Propagation
Transactions, DAG vertices, votes, and checkpoints propagate through a gossip layer (gossip.rs) tuned for low-latency dissemination. Messages are content-addressed by hash so that duplicates are suppressed and a node never forwards the same vertex twice. Because the DAG admits multiple parents per vertex, gossip does not need a single global ordering to make progress — vertices flow as soon as their parents are available.
22.3 Chain Synchronization
A joining or lagging node uses the sync subsystem (sync.rs) to catch up. Rather than replaying every historical signature, a node syncs to the latest finalized checkpoint and then streams DAG vertices forward from there. Finalized checkpoints act as trust anchors (weak subjectivity): a node that knows a recent finalized checkpoint can validate everything after it without trusting any individual peer.
22.4 Data Availability
Each shard maintains a data-availability layer using erasure-coded blobs. Cross-shard transactions (Dynamic Sharding section) include a Merkle proof of availability that the target shard can verify without downloading the full blob, so a shard can confirm that the data backing an inbound message exists and is retrievable without bearing the full bandwidth cost of fetching it.
22.5 Network-Layer Defences
The network is hardened against topology-level attacks by the security subsystem (Security Model section): peer diversity across ASNs and geographies, anchor peers, and connection-validity checks defend against eclipse attacks; rate limiting and proof-of-work admission defend against DoS; and NTP-based time synchronization with outlier filtering defends against time-warp attacks. These are described in the Security Model.