Editing Network topology (section)

==Classification==
The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain.<ref name="Bicsi, B. 2002">{{cite book |author=Bicsi, B. |date=2002 |title=Network Design Basics for Cabling Professionals |publisher=McGraw-Hill Professional |isbn=9780071782968}}</ref>

===Point-to-point===
{{main article|Point-to-point (telecommunications)}}
The simplest topology with a dedicated link between two endpoints. Easiest to understand, of the variations of point-to-point topology, is a point-to-point [[communication channel]] that appears, to the user, to be permanently associated with the two endpoints. A child's [[tin can telephone]] is one example of a ''physical dedicated'' channel.

Using [[circuit-switching]] or [[packet-switching]] technologies, a point-to-point circuit can be set up dynamically and dropped when no longer needed. Switched point-to-point topologies are the basic model of conventional [[telephony]].

The value of a permanent point-to-point network is unimpeded communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers and has been expressed as [[Metcalfe's Law]].

===Daisy chain===
[[Daisy chain (electrical engineering)|Daisy chaining]] is accomplished by connecting each computer in series to the next.  If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination.  A daisy-chained network can take two basic forms: linear and ring.

* A '''[[Linear bus topology|linear topology]]''' puts a two-way link between one computer and the next.  However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
* By connecting the computers at each end of the chain, a '''[[ring topology]]''' can be formed. When a [[Node (networking)|node]] sends a message, the message is processed by each computer in the ring.  An advantage of the ring is that the number of transmitters and receivers can be cut in half. Since a message will eventually loop all of the way around, transmission does not need to go both directions.  Alternatively, the ring can be used to improve fault tolerance. If the ring breaks at a particular link then the transmission can be sent via the reverse path thereby ensuring that all nodes are always connected in the case of a single failure.

===Bus===
[[File:BusNetwork.svg|thumb|Bus network topology]]
{{Main article|Bus network}}
In local area networks using bus topology, each node is connected by interface connectors to a single central cable. This is the 'bus', also referred to as the [[Backbone network|backbone]], or [[Trunk (telecommunications)|trunk]]&nbsp;– all [[data transmission]] between nodes in the network is transmitted over this common transmission medium and is able to be [[Receiver (Information Theory)|received]] by all nodes in the network simultaneously.<ref name="Groth"/>

A signal containing the address of the intended receiving machine travels from a source machine in both directions to all machines connected to the bus until it finds the intended recipient, which then accepts the data. If the machine address does not match the intended address for the data, the data portion of the signal is ignored. Since the bus topology consists of only one wire it is less expensive to implement than other topologies, but the savings are offset by the higher cost of managing the network. Additionally, since the network is dependent on the single cable, it can be the [[single point of failure]] of the network. In this topology data being transferred may be accessed by any node.

====Linear bus====
In a linear bus network, all of the nodes of the network are connected to a common transmission medium which has just two endpoints. When the electrical signal reaches the end of the bus, the signal is reflected back down the line, causing unwanted interference.  To prevent this, the two endpoints of the bus are normally terminated with a device called a [[Electrical termination|terminator]].

====Distributed bus====
In a distributed bus network, all of the nodes of the network are connected to a common transmission medium with more than two endpoints, created by adding branches to the main section of the transmission medium&nbsp;– the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology because all nodes share a common transmission medium.

===Star===
{{Main article|Star network}}
[[File:StarNetwork.svg|thumb|Star network topology]]
In star topology (also called hub-and-spoke), every peripheral node (computer workstation or any other peripheral) is connected to a central node called a hub or switch. The hub is the server and the peripherals are the clients. The network does not necessarily have to resemble a star to be classified as a star network, but all of the peripheral nodes on the network must be connected to one central hub. All traffic that traverses the network passes through the central hub, which acts as a [[Repeater|signal repeater]]. 

The star topology is considered the easiest topology to design and implement.  One advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Also, since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters.

====Extended star====
The extended star network topology extends a physical star topology by one or more repeaters between the central node and the [[peripheral]] (or 'spoke') nodes. The repeaters are used to extend the maximum transmission distance of the physical layer, the point-to-point distance between the central node and the peripheral nodes. Repeaters allow greater transmission distance, further than would be possible using just the transmitting power of the central node. The use of repeaters can also overcome limitations from the standard upon which the physical layer is based.

A physical extended star topology in which repeaters are replaced with hubs or switches is a type of hybrid network topology and is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.

A physical hierarchical star topology can also be referred as a tier-star topology. This topology differs from a [[tree topology]] in the way star networks are connected together. A tier-star topology uses a central node, while a tree topology uses a central bus and can also be referred as a star-bus network.

====Distributed star====
A distributed star is a network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion&nbsp;– i.e., 'daisy-chained'&nbsp;– with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').

===Ring===
{{Main article|Ring network}}
[[File:RingNetwork.svg|thumb|Ring network topology]]

A ring topology is a [[Daisy chain (electrical engineering)|daisy chain]] in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (retransmit) the data to keep the signal strong.<ref name="Inc, S. 2002"/> Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to retransmit data, it severs communication between the nodes before and after it in the bus.

Advantages:
* When the load on the network increases, its performance is better than bus topology.
* There is no need of network server to control the connectivity between workstations.

Disadvantages:
* Aggregate network bandwidth is bottlenecked by the weakest link between two nodes.

===Mesh===
{{Main article|Mesh networking}}
The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by [[Reed's Law]].

====Fully connected network====
[[File:NetworkTopology-FullyConnected.png|thumb|Fully connected mesh topology]]

In a ''fully connected network'', all nodes are interconnected. (In [[graph theory]] this is called a [[complete graph]].) The simplest fully connected network is a two-node network. A fully connected network doesn't need to use [[packet switching]] or [[Broadcasting (networking)|broadcasting]]. However, since the number of connections grows quadratically with the number of nodes:

<math>c= \frac{n(n-1)}{2}.\,</math>

This makes it impractical for large networks.  This kind of topology does not trip and affect other nodes in the network.

====Partially connected network====
[[File:NetworkTopology-Mesh.svg|thumb|Partially connected mesh topology]]
In a partially connected network, certain nodes are connected to exactly one other node; but some nodes are connected to two or more other nodes with a point-to-point link. This makes it possible to make use of some of the redundancy of mesh topology that is physically fully connected, without the expense and complexity required for a connection between every node in the network.

===Hybrid===
Hybrid topology is also known as hybrid network.<ref>{{Cite web|title=What is Hybrid Topology ? Advantages and Disadvantages|url=http://www.orosk.com/hybrid-topology/|url-status=dead|archive-url=https://web.archive.org/web/20160909170820/http://www.orosk.com/hybrid-topology/|archive-date=September 9, 2016|access-date=2018-01-26|website=OROSK.COM|language=en-US}}</ref> Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a [[tree network]] (or ''star-bus network'') is a hybrid topology in which [[star network]]s are interconnected via [[bus network]]s.<ref name="Sosinsky">{{cite book |title=Networking Bible |last=Sosinsky |first=Barrie A. |page=16 |date=2009 |location=Indianapolis |publisher=Wiley Publishing |isbn=978-0-470-43131-3 |oclc=359673774 |chapter=Network Basics |chapter-url=https://books.google.com/books?id=3DOREqRZejcC&pg=PA16 |access-date=2016-03-26}}</ref><ref>{{cite book |url=https://books.google.com/books?id=gnuwPpBcO-MC&pg=RA1-PT12 |title=Understanding Computer Science (for Advanced Level): The Study Guide |last=Bradley |first=Ray |location=Cheltenham |publisher=[[Nelson Thornes]] |page=244 |isbn=978-0-7487-6147-0 |oclc=47869750 |access-date=2016-03-26|year=2001 }}</ref> However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected.

A ''star-ring'' network consists of two or more ring networks connected using a [[Media Access Unit|multistation access unit]] (MAU) as a centralized hub.

''Snowflake'' topology is meshed at the core, but tree shaped at the edges.<ref>{{citation |url=https://datatracker.ietf.org/doc/rfc5439/ |title=An Analysis of Scaling Issues in MPLS-TE Core Networks RFC 5439 |date=February 2009 |access-date=2024-08-05 |last1=Farrel |first1=Aian |last2=Komolafe |first2=Olufemi |last3=Yasukawa |first3=Seisho }}</ref>

Two other hybrid network types are ''hybrid mesh'' and ''hierarchical star''.<ref name="Sosinsky"/>