Understanding Symmetric and Asymmetric Networking Technology

Most home routers use asymmetric technology

The Network of the Office Building and Road Intersection
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In a symmetric computer network, all devices transmit and receive data at equal rates. Asymmetric systems support more bandwidth in one direction than the other.

Reasons for Choosing Asymmetric Over Symmetric Tech

With the rise of streaming movies and television shows online, the typical home router downloads more data than a family is ever likely to upload. Most home routers can handle this discrepancy between the amount of downloaded data and uploaded data. In many cases, the cable or satellite company itself provides higher 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. Symmetric DSL supports equal bandwidth in both directions. Internet services for home use usually support ADSL because internet users tend to download much more data than they upload. Business networks, which regularly send and receive data, use SDSL more often.

Symmetric vs. Asymmetric in Networking

Symmetry and asymmetry also apply to network design in more general ways. Symmetric network design gives all devices equal access to resources. Asymmetric networks segregate access to resources unequally. For example, "pure" P2P systems that don't use centralized servers are symmetric. Other P2P networks are asymmetric.

In network security, both symmetric and asymmetric forms of encryption exist. Symmetric encryption systems share the same encryption keys between both ends of the communication. Asymmetric encryption systems use different encryption keys on each communication endpoint. Some of these keys might be public. Others may be private.