It uses a special three-byte frame called a token that is passed around a logical ring of workstations or servers. This token passing is a channel access method providing fair access for all stations, and eliminating the collisions of contention-based access methods.
In 1988 the faster 16 Mbit/s Token Ring was standardized by the 802.5 working group. An increase to 100 Mbit/s was standardized and marketed during the wane of Token Ring's existence and was never widely used. While a 1000 Mbit/s standard was approved in 2001, no products were ever brought to market and standards activity came to a standstill as Fast Ethernet and Gigabit Ethernet dominated the local area networking market.
Stations on a Token Ring LAN are logically organized in a ring topology with data being transmitted sequentially from one ring station to the next with a control token circulating around the ring controlling access. Similar token passing mechanisms are used by ARCNET, token bus, 100VG-AnyLAN (802.12) and FDDI, and they have theoretical advantages over the CSMA/CD of early Ethernet.
Every station in a Token Ring network is either an active monitor (AM) or standby monitor (SM) station. There can be only one active monitor on a ring at a time. The active monitor is chosen through an election or monitor contention process.
The active monitor performs a number of ring administration functions. The first function is to operate as the master clock for the ring in order to provide synchronization of the signal for stations on the wire. Another function of the AM is to insert a 24-bit delay into the ring, to ensure that there is always sufficient buffering in the ring for the token to circulate. A third function for the AM is to ensure that exactly one token circulates whenever there is no frame being transmitted, and to detect a broken ring. Lastly, the AM is responsible for removing circulating frames from the ring.
Token Ring stations must go through a 5-phase ring insertion process before being allowed to participate in the ring network. If any of these phases fail, the Token Ring station will not insert into the ring and the Token Ring driver may report an error.
Systems Network Architecture (SNA) is IBM's proprietary networking architecture, created in 1974. It is a complete protocol stack for interconnecting computers and their resources. SNA describes formats and protocols but, in itself, is not a piece of software. The implementation of SNA takes the form of various communications packages, most notably Virtual Telecommunications Access Method (VTAM), the mainframe software package for SNA communications.
Within SNA there are three types of data stream to connect local display terminals and printers; there is SNA Character String (SCS), used for LU1 terminals and for logging on to an SNA network with Unformatted System Services (USS), there is the 3270 data stream mainly used by mainframes such as the System/370 and successors, including the zSeries family, and the 5250 data stream mainly used by minicomputers/servers such as the System/34, System/36, System/38, and AS/400 and its successors, including System i and IBM Power Systems running IBM i.
The proprietary networking architecture for Honeywell Bull mainframes is Distributed Systems Architecture (DSA). The Communications package for DSA is VIP. DSA is also no longer supported for client access. Bull mainframes are fitted with Mainway for translating DSA to TCP/IP and VIP devices are replaced by TNVIP Terminal Emulations (GLink, Winsurf). GCOS 8 supports TNVIP SE over TCP/IP.
The networking architecture for Univac mainframes was the Distributed Computing Architecture (DCA), and the networking architecture for Burroughs mainframes was the Burroughs Network Architecture (BNA); after they merged to form Unisys, both were provided by the merged company. Both were largely obsolete by 2012. International Computers Limited (ICL) provided its Information Processing Architecture (IPA).
DECnet is a suite of network protocols created by Digital Equipment Corporation, originally released in 1975 to connect two PDP-11 minicomputers. It evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s.
SNA initially aimed at competing with ISO's Open Systems Interconnection, which was an attempt to create a vendor-neutral network architecture that failed due to the problems of "design by committee". OSI systems are very complex, and the many parties involved required extensive flexibilities that hurt the interoperability of OSI systems, which was the prime objective to start with.
A network is more than simply a collection of machines and communication lines. A properly designed network serves a particular purpose for a particular user or class of users. In order to design networks for different users and purposes while minimizing design effort, one can employ a network architecture. In this chapter we look at the services provided by a network, examine what an architecture is, and then look at Systems Network Architecture (SNA),* its design principles and how it enables a network to provide the required services. Our discussion of the architecture appears in two major sections, transporting data and distributed programming. We have attempted to minimize the amount of jargon in this description of SNA. Necessary new terms are introduced in italics. After looking at the architecture, we conclude with a discussion of how SNA has applied the underlying principles.
A ring topology is a network architecture in which devices are connected in a ring structure and send information to each other based on their ring node's neighbouring node. As compared to the bus topology, a ring topology is highly efficient and can handle heavier loads. Because packets may only travel in one direction, most Ring Topologies are referred to as one-way unidirectional ring networks. Generally, Bidirectional and Unidirectional are the two types of ring topology. On the basis of devices that are being linked together to form a network, several kinds of ring topology setups work differently.
This topology may be used in LANs or WANs. Depending on the network card used in each computer, an RJ-45 network cable or a coaxial cable is used to connect computers in a ring topology. The advantages of a ring topology include, it does not need a central hub in order to function. Installation and troubleshooting with this type of network are also very easy as compared to other networks.
A ring architecture has the drawback that if one node fails to send data, the entire network suffers. Therefore, some of the ring topology setups use a dual-ring structure to resolve this problem. In a dual-ring structure, the information is transmitted into clockwise and counter-clockwise directions. There is a backup way of transmission in case one transmission fails; these systems are known as redundant ring structures.
In a ring topology, each device is connected to two other devices, and several of these structures are linked together to form a circular route known as a ring network. To reach the data destination, the In-Ring Topology uses a one-to-one procedure; data is communicated from one device to the next, and the process is repeated until the data reaches the target. Sending node transmitted data to the destination node with the help of tokens. Therefore, it is called Token Ring Topology. It is also known as Active Topology since it requires all nodes to be active in order for transmission to continue.
Unidirectional Ring: A half-duplex network is one that permits data to be transferred in just one direction, either clockwise or counter-clockwise. Generally, most ring networks use the process to flow data in only one direction.
Bidirectional Ring: It is also known as a dual-ring network, and it may be used to turn a unidirectional network into a bidirectional network by using two links between two network nodes. While sending data in one direction, if any of the intermediate nodes get fail down, dual rings offer alternate paths for any node to reach its destination.
Early, the ring topology was most widely used in small buildings like offices, schools. However, in modern times, this type of technology is rarely used. For stability, performance, or support, it has been switched to other types of network.
Most people have used token-based process in some form. For example, gaining access to an online account by entering a code sent as a one-time password, using a fingerprint to unlock a mobile phone, and accessing a website through a Facebook login are all common examples.
Disconnected tokens enable users to verify their identity by issuing a code they then need to enter manually to gain access to a service. A good example of this is entering a code on a mobile phone for two-factor authentication (2FA).
Authentication tokens and 2FA play a key role in establishing zero-trust network access control. This approach is crucial as users increasingly access corporate resources from remote locations and due to the increase in unknown devices accessing networks. The risk of stolen credentials means businesses must establish trust that a user is who they claim to be before providing access to their resources. Secure authentication enables organizations to identify users entering their networks and block devices or people that are not authorized.
The Fortinet identity and access management (IAM) solution enables organizations to identify devices and users as they enter their networks. They can then control and manage identities to ensure only the right users gain the right level of access to the appropriate resources. The IAM solution includes various products, such as FortiAuthenticator, which prevents unauthorized access through certificate management, guest access management, and SSO services, and FortiToken, which offers further confirmation of user identities by requesting users to provide a second factor of authentication through mobile applications and physical tokens. 2b1af7f3a8