The transmission mode used by the DisplayPort main link is negotiated by the source and sink device when a connection is made, through a process called "Link Training". This process determines the maximum possible speed of the connection. If the quality of the DisplayPort cable is insufficient to reliably handle HBR2 speeds for example, the DisplayPort devices will detect this and switch down to a lower mode to maintain a stable connection. The link can be re-negotiated at any time if a loss of synchronization is detected.