1.1.e Explain TCP operations

1.1.e [vi] Global synchronization

Global synchronization happens when multiple TCP hosts reduce their transmission rates in response to packet dropping, then increase their transmission rates once again when the congestion is reduced.

WRED avoids the globalization problems that occur when tail drop is used as the congestion avoidance mechanism on the router.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1144-1147).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfconav.html