Ethernet
The popular Ethernet family defines common medium dependent interfaces. For 10BASE5 connection to the coaxial cable was made with either a vampire tap or a pair of N connectors. For 10BASE2 the connection to the coaxial cable was typically made with a single BNC connector to which a T-piece was attached. For twisted pair cabling 8P8C modular connectors are used (often called "RJ45" in this context). For fiber a variety of connectors are used depending on manufacturer and physical space availability.
With 10BASE-T and 100BASE-TX separate twisted pairs are used for the two directions of communication. Since twisted pair cables are conventionally wired pin to pin there are two different pinouts used for the medium dependent interface. These are referred to as MDI and MDI-X (medium dependent interface crossover). When connecting a MDI port to an MDI-X port a straight through cable is used while to connect two MDI ports or two MDI-X ports a crossover cable must be used. Conventionally MDI is used on end devices while MDI-X is used on hubs and switches. Some network hubs or switches have an MDI port (often switchable) in order to connect to other hubs or switches without a crossover cable.
Read more about this topic: Medium Dependent Interface