When packets collide, the PCs that sent them are instantly notified, and each chooses a random interval to wait before it resends the packet. This approach helps prevent network gridlock. Though the ethernet specification accounts for many topologies, the most popular configuration is called the star topology. Hubs receive packets from one node and distribute them to other nodes. You can also run ethernet over a bus topology, in which the computers branch off from one main line.
Star topologies are easier to manage than bus topologies and use less expensive wiring.
But you don't have to create a whole LAN to use ethernet. Ethernet is also commonly used to connect PCs to high-speed Internet devices, such as cable or DSL modems. The specification also details how fast data can travel and the types of wires that must be used. For a long time, 10Base-T ethernet, capable of passing 10 megabits of data per second, was the fastest and most popular implementation. To get that much more speed, Fast Ethernet uses higher-quality cabling that sends the packets more quickly without degrading the signal.