PCI-E is a point-to-point bus that provides a non-shared link to a PCI-E device. PCI-E implementaions can scale bandwidth based on the number of lanes implemented in the link. Each lane carries a full-duplex serial data bit stream at a rate of 2.5Gbits/second. T1 and T2-based servers provide links that have either four or eight full-duplex lanes and are referred to as, respectively, x4 or x8 links. Since the links are non-shared, systems typically make use of PCI-E switches to connect to onboard devices and slots for external device connections.