A primary disadvantage is that the customer and the carrier may be looking at vastly different performance data, depending on the locations and types of equipment involved. Carriers and customers will have no easy way to verify each other's performance claims. Furthermore, carriers will have limited visibility of the last few kilometers of a circuit, since performance data from the customer's site will be available to the customer only. The ideal situation is for both the carrier and the customer to have access to as much network performance data as possible. With this data, both parties can quickly identify a problem, isolate it to a particular portion of the network, and correct it.
Carriers benefit from more efficient maintenance.
Customers benefit from increased uptime. And a strong relationship is fostered between the customer and the carrier. The same performance data can be accessed by both carriers and customers. The location of PMUs in the network is ideal for gathering and reporting performance data. Because PMUs are installed at the customer premises, at the interface between the customer and carrier portions of an E1 circuit, they provide a critical point of demarcation.