Editing Network topology (section)

==Topologies==
[[File:NetworkTopologies.svg|right|thumb|300px|Diagram of different network topologies]]

Two basic categories of network topologies exist, physical topologies and logical topologies.<ref name="Inc, S. 2002">Inc, S., (2002) . Networking Complete. Third Edition. San Francisco: Sybex</ref>

The [[transmission medium]] layout used to link devices is the physical topology of the network. For conductive or fiber optical mediums, this refers to the layout of [[Structured cabling|cabling]], the locations of nodes, and the links between the nodes and the cabling.<ref name="Groth"/> The physical topology of a network is determined by the capabilities of the network access devices and media, the level of control or fault tolerance desired, and the cost associated with cabling or telecommunication circuits.

In contrast, logical topology is the way that the signals act on the network media,<ref>{{citation |url=http://www.webopedia.com/quick_ref/topologies.asp |title=What Are Network Topologies? |date=5 May 2011 |access-date=2016-09-17}}</ref> or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.<ref>{{Cite journal |author1=Leonardi, E. |author2=Mellia, M. |author3= Marsan, M. A. |date=2000 |title=Algorithms for the Logical Topology Design in WDM All-Optical Networks |url=https://www.researchgate.net/publication/2414623 |journal=Optical Networks Magazine |pages=35–46}}</ref> A network's logical topology is not necessarily the same as its physical topology. For example, the original [[twisted pair Ethernet]] using [[repeater hub]]s was a logical bus topology carried on a physical star topology. [[Token Ring]] is a logical ring topology, but is wired as a physical star from the [[media access unit]]. Physically, [[Avionics Full-Duplex Switched Ethernet]] (AFDX) can be a cascaded star topology of multiple dual redundant Ethernet switches; however, the [[Avionics Full-Duplex Switched Ethernet#Virtual links|AFDX virtual links]] are modeled as [[Time-division multiplexing|time-switched]] single-transmitter bus connections, thus following the safety model of a [[ARINC 429|single-transmitter bus topology]] previously used in aircraft. Logical topologies are often closely associated with [[media access control]] methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their [[Router (computing)|router]]s and switches.