Asymmetric vs Symmetric

 

Most multi-subscriber network topologies use aggregation points where many subscriber connections converge. In a wireless network, this is a base station; in a copper network this is a DSLAM at the telephone exchange; in a FTTP network (like the NBN), it’s an OLT at the provider central office.

For slightly different, but nonetheless similar technical reasons, for all of these technologies it is easier to send data from the aggregation point to the subscriber than it is to receive data from the subscriber. The common factor is that the aggregation points have to ‘listen’ to thousands of connections at once, rather than the subscriber who only ‘listens’ to one aggregation point at a time.  The impact on the provider is that more network resources (which cost money) are required to receive data at the aggregation point than to send it.

Single-user, residential and low-cost business grade services are therefore generally sold as ‘asymmetric’, with more download speed than upload, as this approach keeps subscriber costs down. Because this also matches the usage pattern for these user groups, setting up networks for asymmetric use works perfectly well for large numbers of the subscriber community.

But much of the community, especially businesses ‘serving’ data to customers, suppliers and other branches, need broadband connections with as much upload capability as download. In nearly all cases, these symmetric connections cost more than asymmetric connections, and often more than two times the asymmetric equivalent download speed.



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