Understanding Symmetric and Asymmetric Networking Technology

Most home routers use asymmetric technology

The Network of the Office Building and Road Intersection
Dong Wenjie / Getty Images

In a symmetric computer network, all devices transmit and receive data at equal rates. Asymmetric networks, on the other hand, support disproportionately more bandwidth in one direction than the other.

Reasons for Choosing Asymmetric Over Symmetric Tech

With the proliferation of streaming movies and television shows online, the typical home router is asked to download a much greater amount of data in the form of streaming video than a family is ever likely to upload. This is where asymmetric technology comes in handy. Most home routers are set up to handle this discrepancy between the amount of downloaded data and uploaded data. In many cases, the cable or satellite company itself provides greater download speeds than upload speeds for the same reason.

For example, Digital Subscriber Line (DSL) technology exists in both symmetric and asymmetric forms. Asymmetric DSL (ADSL) offers much more bandwidth for downloads by sacrificing bandwidth available for uploads. Conversely, symmetric DSL supports equal bandwidth in both directions. Internet services for home use normally support ADSL because typical internet users tend to download much more data than they upload. Business networks more commonly use SDSL.

Symmetric vs. Asymmetric in Networking

Symmetry and asymmetry also apply to network design in more general ways. A symmetric network design affords all devices equal access to resources, whereas asymmetric networks segregate access to resources unequally. For example, "pure" P2P networks that do not rely on centralized servers are symmetric, while other P2P networks are asymmetric.

Finally, in network security, both symmetric and asymmetric forms of encryption exist. Symmetric encryption systems share the same encryption keys between both ends of network communication. Asymmetric encryption systems use different encryption keys -- such as public and private -- on each communication endpoint.