Most Internet users today tend to download more data than they transmit to other computing devices. Consequently, Internet Service Providers (ISPs) have observed an excess in bandwidth for upstream traffic when compared to downstream traffic. As the growth of content providers continues, Tier-1 ISPs are forced to upgrade their network with additional network equipment to keep up with downstream traffic demands.
The asymmetric growth can be costly to Tier-1 ISPs especially in cases where the content providers are not direct customers.