A LAN is just two or more network-capable devices connected to each other over a small area through a medium, such as a cable. LAN architecture is the set of rules and design principles that define the LAN. A LAN is made up of three components: physical media, such as the cabling and network interfaces; the topology, such as a star or ring topology; and the protocols, or LAN technologies, such as Token Ring or Ethernet.
The topology of a LAN is characterized by its logical form and its physical shape, such as the shape of a star, ring, or a tree. A star topology is also known as a hub-and-spoke because the connecting point of all devices is at the center of the star, much as the hub of a wheel is the center of the wheel spokes. A ring topology is shaped like a circle, in which each device has a connection on both sides to attached devices, so that all devices are connected in a ring.
The topology of the LAN is based in part on the technology used, such as Token Ring, FDDI, or Ethernet. A ring topology is enabled by either a Token Ring or FDDI LAN implementation with an inherent redundancy against failure. This redundancy provides two paths across the LAN from the workstation: one on each side of the workstation. A workstation in a Token Ring or FDDI LAN can send data across the network only when its turn for the token has come around. A star or tree topology is enabled by an Ethernet LAN implementation with no inherent redundancy. Unlike a Token Ring or FDDI workstation, an Ethernet workstation can send data across the network at any time as long as the network is idle, meaning no other workstations are sending data at the same time.