Thunderbolt technology is designed on switched fabric architecture with full duplex links. Thunderbolt port on a computer is capable of providing full bandwidth of link in both directions simultaneously. There is no sharing of ports for upstream and downstream directions. Thunderbolt architecture can be defined in 4 layers as: PCIe and Display Port, Common Transport Layer, Electrical/Optical Layer and Connector and Cable. The heart of the Thunderbolt architecture is the Transport Layer. This layer is based on a high performance, low-power consuming switching architecture. Thunderbolt follows a symmetric architecture which supports multiple topologies and enables peer-to-peer communication. It has a novel time synchronisation protocol that allows all Thunderbolt products like Thunderbolt external hard drive to synchronise their time within Bns of each other. It allows the multiplexing of PCIe transactions with Display Port communication on the same link. The PCIe and Display ports are mapped onto the same transport layer which is responsible for encapsulation of mapped protocol information.