Non-fiction: Ethernet (Xerox PARC technical memorandum, with David R. Boggs)

Overview
The 1973 Xerox PARC technical memorandum by Bob Metcalfe, with David R. Boggs, lays out the first practical design for what became known as Ethernet. It describes a simple, robust method for sharing a common coaxial cable among many Alto workstations, emphasizing low cost, ease of wiring, and tolerance for a high density of interactive terminals. The memorandum frames the network as an experiment in local-area communications that blends theoretical insight with hands-on implementation choices.

Network architecture
The architecture uses a single shared, flattened coaxial medium where each host attaches via a transceiver. Messages are transmitted as variable-length packets onto the cable and are received by all attached machines. The design treats the cable as a "broadcast" environment, with addressing and simple packet formats allowing hosts to accept or ignore frames based on destination identifiers. Physical design choices favor short, manageable cable runs and simple connectors to keep setup and maintenance practical for a research environment.

CSMA/CD: Rationale and mechanics
A central contribution is the adoption of Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as the medium-access control method. Inspired by earlier random-access ideas like ALOHAnet, the memorandum argues that sensing the carrier before transmitting reduces the likelihood of collisions, while actively detecting collisions during transmission permits immediate termination and retransmission. This approach balances throughput and latency on a busy shared medium and avoids the overhead of strict arbitration or time-slotting, making it suitable for interactive computing.

Implementation on Alto systems
Practical details describe how the transceivers and interface circuitry were integrated with Alto workstations at PARC. The memorandum documents signal levels, encoding choices, and pragmatic tradeoffs for transceiver placement and cable topology. Emphasis is placed on simplicity: inexpensive electronics and straightforward packet handling within the host keep per-node cost low, while the shared medium and common packet format allow heterogeneous software to interoperate through a minimal hardware layer.

Experimental findings and performance
Empirical observations from the Alto deployment underpin many recommendations. Measurements and on-the-ground experience show that CSMA/CD achieves acceptable throughput under typical interactive loads and that short propagation delays on the local cable limit the window in which collisions can occur. The memorandum reports on collision frequency, effective throughput, and the responsiveness of retransmission strategies, arguing that the design meets the needs of a research lab network where many short requests and responses dominate traffic patterns.

Impact and legacy
The ideas and implementation choices in this early memorandum proved foundational for later standardization and widespread adoption. The simple, resilient approach to sharing a wired medium influenced the IEEE 802.3 standard and guided the evolution of Ethernet through higher speeds and more complex topologies. Beyond technical specifics, the document demonstrates how careful experimentation and pragmatic engineering can turn a modest research prototype into a family of technologies that reshaped computing practice.