Thinnet

Thinnet, commonly referred to as Thin Ethernet or 10BASE2, is an early Ethernet networking standard that uses thin coaxial cable (RG-58) and BNC connectors to form a shared bus. It operates at 10 megabits per second and was introduced as a cheaper, more flexible alternative to Thicknet (10BASE5) in the late 1980s.

Physically, thinnet uses 50-ohm RG-58 coax. A single segment can run up to 185 meters and supports up to about 30 network devices. Each device connects to the bus through a BNC T-connector or similar inline connector, and both ends of the segment must be terminated with 50-ohm terminators to suppress reflections. The topology is a linear bus; multiple segments can be joined with repeaters, but this introduces additional latency and complexity.

Media access control is CSMA/CD; all devices share the same collision domain. Devices transmit when the channel is free, and collisions cause stations to back off. Because of the shared medium, thinnet performance degrades as traffic increases, and the practical limit is roughly 30 nodes per segment to maintain reliability.

Thinnet was widely used through the 1990s before gradually being superseded by Ethernet over twisted pair (10BASE-T and later standards). Its simplicity and low cost were advantages, but its reliance on a single coaxial bus, susceptibility to faults along the cable, and limitations in segment length and node count contributed to its decline. Today it is largely obsolete but may still appear in historical or legacy networks.