Editing Ring network (section)

{{Short description|Network topology in which nodes form a ring}}
{{more citations needed|date=December 2007}}

[[Image:RingNetwork.svg|thumb|Image showing ring network layout]]

A '''ring network''' is a [[network topology]] in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node – a ring. Data travels from node to node, with each node along the way handling every packet.

Rings can be unidirectional, with all traffic travelling either clockwise or anticlockwise around the ring, or bidirectional (as in [[Synchronous optical networking|SONET/SDH]]).<ref>{{cite book | url=https://books.google.com/books?id=bwUNZvJbEeQC&dq=ring+network+unidirectional&pg=PA509 | title=Data Communications and Networking | isbn=9780072967753 | last1=Forouzan | first1=Behrouz A. | year=2007 | publisher=Huga Media }}</ref> Because a unidirectional ring topology provides only one pathway between any two nodes, unidirectional ring networks may be disrupted by the failure of a single link.<ref name="about_article">{{cite web|author1=Bradley Mitchell|title=Introduction to Computer Network Topology|url=http://compnetworking.about.com/od/networkdesign/a/topologies.htm|website=About.com|access-date=January 18, 2016}}</ref> A node failure or cable break might isolate every node attached to the ring. In response, some ring networks add a "counter-rotating ring" (C-Ring) to form a redundant topology: in the event of a break, data are wrapped back onto the complementary ring before reaching the end of the cable, maintaining a path to every node along the resulting C-Ring. Such "dual ring" networks include the [[ITU-T]]'s [[PSTN]] telephony systems network [[Signalling System No. 7]] (SS7), [[Spatial Reuse Protocol]], [[Fiber Distributed Data Interface]] (FDDI), [[Resilient Packet Ring]], and [[Ethernet Ring Protection Switching]]. [[IEEE 802.5]] networks – also known as IBM Token Ring networks – avoid the weakness of a ring topology altogether: they actually use a ''star'' topology at the ''physical'' layer and a [[media access unit]] (MAU) to ''imitate'' a ring at the ''datalink'' layer. Ring networks are used by ISPs to provide data backhaul services, connecting the ISP's facilities such as central offices/headends together.<ref>{{cite book | url=https://books.google.com/books?id=rP5gBgAAQBAJ&dq=ring+topology+collision&pg=RA1-PA9 | title=Mobile Computing Deployment and Management: Real World Skills for CompTIA Mobility+ Certification and Beyond | isbn=9781118824610 | last1=Bartz | first1=Robert J. | date=24 February 2015 | publisher=John Wiley & Sons }}</ref><ref>[https://openaccess.uoc.edu/bitstream/10609/18805/6/amerinoraTFC0113memoria.pdf Implementación de DOCSIS 3.0 sobre redes HFC]. ''openaccess.uoc.edu.'' Retrieved 26 January 2024</ref>

All [[Signalling System No. 7]] (SS7), and some SONET/SDH rings have two sets of bidirectional links between nodes. This allows maintenance or failures at multiple points of the ring usually without loss of the primary traffic on the outer ring by switching the traffic onto the inner ring past the failure points.