Abstract

Distributed networks are composed of spatially separated processes that communicate exclusively through message exchange without the oversight of a central control center. No single global time exists across these networks because independent physical clocks are not perfectly accurate and message transmission delay is significant relative to the time between local events. Although state transitions may be deterministic, a process cannot observe the actions of others until it receives a message. This delay between event occurrence and system-wide visibility permits divergent local histories until a canonical history is selected by protocol.

Introduction

Time is commonly treated as a single ordered axis: event a precedes event b because it occurs earlier on a shared clock. This assumption implies a universal reference that is accessible to all participants in a system.

Distributed networks violate this requirement. Processes are spatially separated and interact only through message exchange. Propagation delay is non-negligible and path-dependent, while physical clocks drift. As a result, simultaneity is not a primitive of the system and global “earlier/later” is not decidable for concurrent events.

This document records neutral system properties that determine how time is represented and how ordering is established in distributed networks and transactional ledgers. It describes the constraints that shape local observation of “now” and the mechanisms by which systems recover consistent ordering without relying on a global clock.

I. Definitions

  • Distributed System: A collection of distinct processes that are spatially separated and communicate with one another by exchanging messages.

  • Internet: A collection of interconnected networks (“network of networks”) enabling communication between machines using standardized protocols.

  • Packet: A segment of a message consisting of a payload and a header used for routing and reassembly.

  • Protocol: A standardized set of rules for formatting messages and coordinating actions between devices.

  • Transactional Singleton Machine (Ethereum): A transaction-based state machine with shared state that advances through valid state transitions.

  • Happened-Before Relation (→): A partial ordering where one event precedes another if they occur in the same process or are linked by message send/receive.

  • Logical Clock: A counter-based mechanism that assigns timestamps to events without assuming physical time.

II. System Model

A distributed system is composed of processes, each containing an a priori ordered sequence of local events. The network has no central control center and does not depend on any single machine for correctness or availability. Communication occurs by transmitting encoded information through physical media, and delivery is constrained by propagation and routing.

In transactional ledgers, transactions are collated into blocks and chained via cryptographic hashes to record a sequence of state transitions. Nodes reach local conclusions based on received messages and locally executed verification, not on a shared global time reference.

III. Network Time Properties

No single global time exists in the network because physical clocks are imperfect and diverge over time, and because message transmission delay is non-negligible relative to local event rates. Packets may traverse different routes and arrive unpredictably, so arrival order cannot be assumed to match send order.

Ethereum reflects these constraints in its scheduling conventions: earlier versions used block numbers as a logical trigger for certain protocol changes, while later versions schedule some changes against block timestamps. In both cases, the effective ordering experienced by nodes remains conditional on propagation and local observation.

IV. Observation and Visibility

Absolute simultaneity is not available as a system primitive. An event can influence another only through message exchange, and a process cannot observe remote actions until a corresponding message is received. Two events are concurrent when neither causally affects the other, making global “first” undefined without additional rules.

Decentralized ledgers may temporarily admit multiple candidate histories (“forks”) because different nodes observe different message subsets at different times. Canonical history is not an immediate fact of the network; it is the result of protocol-defined selection under incomplete and asynchronous observation.

V. Ordering Without a Global Clock

Ordering is established by enforcing a clock condition: if event a happened before b, then the timestamp assigned to a must be less than the timestamp assigned to b. Logical clocks implement this by incrementing between local events and advancing upon receipt of messages to exceed observed timestamps.

A total order is obtained by sorting events by logical timestamps and breaking ties through an arbitrary ordering of processes. At the network layer, packet headers enable reassembly independent of arrival order. At the ledger layer, consensus protocols select a canonical history to resolve divergent local views.

Core Finding

No single global time exists in distributed networks. Time is represented operationally as causal structure and enforced ordering under non-negligible delay, imperfect clocks, and asynchronous observation.