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symmetric and asymmetric


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

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 (SDSL) supports equal bandwidth in both directions. Internet services for home normally provide ADSL as typical Internet users tend to download much more data than they upload. Business networks more commonly use SDSL.

Besides DSL networking, the terms "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. Symmetic 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.

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