Thicknet

Thicknet, also known as 10BASE5, is an early Ethernet technology that used a thick coaxial cable as its transmission medium. It supports a 10 Mbit/s data rate and uses CSMA/CD with Manchester encoding. The network operates as a bus, with a single trunk that runs the length of the segment and terminators at both ends to prevent signal reflections.

In practice, Thicknet employed a relatively thick coaxial cable (about one inch in diameter) into which devices connected using vampire taps. Each device attaches to the trunk with a drop cable via a tap, and a Medium Attachment Unit (MAU) on the device side provides the AUI interface to the host network adapter. Termination resistors of about 50 ohms were placed at each end of the trunk.

Physical layout required careful planning, with maximum segment lengths around 500 meters and a practical limit on the number of connected devices per segment (typically on the order of a hundred). The standard used Manchester coding at 10 Mbps and CSMA/CD to manage access to the shared medium.

Thicknet provided a robust, centralized bus solution for early Ethernet but was relatively inflexible and difficult to install and maintain. It required precise termination, regular maintenance of taps and connectors, and was sensitive to faults along the coax. By the mid-1990s, Thicknet gradually declined as Ethernet moved to thinner coax and, ultimately, twisted-pair Ethernet (10BASE-T), which offered easier installation and expansion.