Pooling, Multiplexing Changes Complicate Upgrades

Multiplexing and pooling reduce the number of devices or users that directly access Microsoft servers, and Microsoft has rules in place to ensure that customers purchase enough Client Access Licenses (CALs) for servers that require them. Microsoft’s definitions of multiplexing and pooling have become broader, however, triggering new CAL requirements. The changes could substantially boost Microsoft’s revenues, but they are complex and Microsoft has not documented all of them. Customers should not undertake upgrades or staged migrations without written commitments from Microsoft and a clear understanding of the multiplexing rules, or they could find themselves liable for unbudgeted costs.

Multiplexing and Pooling

Multiplexing and pooling refer to techniques used to reduce the number of physical or logical connections between two points through some form of sharing.

Multiplexing is best known as a telecommunications technology—multiplexors are used to aggregate multiple signals so they can be sent across a single wire, with signals kept separate by giving each a slice of transmission time or a dedicated frequency. The consolidated signal is disaggregated at the transmission endpoint.