Network Topologies Definition

Network Topologies

Network. An interconnected system that allows communication between one or more connections points, in one or more directions. An interconnection of three or more communicating entities. 2. An interconnection of usually passive electronic components that performs a specific function (which is usually limited in scope), e.g., to simulate a transmission line or to perform a mathematical function such as integration or differentiation. Note: A network may be part of a larger circuit. All the different networks types shown below may be interconnected into hybrid networks, but only the common ones are shown.

Network Topology. The specific physical, i.e., real, or logical [virtual], arrangement of the elements of a network. The Network Topology describes how the network is connected together. There are many possible interface topologies, with the seven common topologies shown in the graphic below. However any interface topology may be combined with any other topology forming a hybrid interconnect not listed below.

All the highest speed buses are Point-to-Point, but that could relate to many of the bus topologies listed below. A Point-to-Point interface could be a Driver to Receiver or Driver to Switch [as in Mesh or Star].

Bus Network: Also called Multi-Drop. The EIA-485 interface [EIA/TIA-485] is the classic example of a Bus Network. The RS485 may be connected with up to 32 transmitters or 32 receivers in any combination. Ethernet is another example of a Multi-Drop Network. Ethernet uses a Collision Detection routine [CSMA/CD] to determine when access to the bus is available, allowing any number of drivers [transmitters] on the network.

Bus Topology: A network topology in which all nodes, i.e., stations, are connected together by a single bus.

Cascaded Star Topology: A Cascaded Star Network is a configuration of a Star Network [below] which uses hubs on the spokes of the Star to expand or cascade the network into additional Star Networks. So a Cascaded Star Network is a Multi-Star network.

Chained Interface: Same as a line or Daisy Chained interface.

Chip-to-Chip Network: A single connection interface that connects one Integrated Circuit to one other Integrated Circuit. The ONFI NAND bus would be considered a Chip-to-Chip Network. The Accelerated Graphics Port [AGP] is also an example of a Chip-to-Chip interface bus, or really Board-to-Board interface. A Chip-to-Chip Network would also be a Point-to-Point Topology, but restricted to ICs.

Cluster Network: The same as a Mesh Topology or Fully Connected Topology. A Cluster Network might be found being used in a VPX System, or HyperTransport Architecture. Each node is connected to every other node in a cluster or mesh network, as shown by the connection points.

Cluster Network

Compound Ring: Two independent Ring Networks interconnected at one node. See Ring Network.

Compound Star: Two or more Star networks interconnected at one node. The diagram shows three networks interconnected but any number of networks are possible. Only the central node of the star network is connected to another star network. See Star Network.

Daisy Chained Network. Also called a linear network or Line network. A interconnection architecture that connects components in a line, one after the other. An Interface Bus Architecture where one node on the bus feeds only one other node and only receives information from only one node.

Distributed Network: A network structure in which the network resources, such as switching equipment and processors, are distributed throughout the geographical area being served. In a Distributed Network control may be centralized or distributed.

Dual Bus: A pair of parallel buses arranged such that the direction of data flow in one bus is opposite to the direction of data flow in the other bus.

Dual Ring Network: Similar to a Ring Network, but a Dual Ring Topology allows traffic to flow in opposite directions, with one ring counter-rotating to the other. Normally in a Dual Ring network one ring is the primary path while the secondary ring is the secondary path [or backup path]. SONET is an example of a network that may use a Dual-Ring topology.

Dual Star: Two independent Star networks that have been interconnected via their central hub and connect to each node. A Star network with two central hubs. Although not shown in the traditional star shape, both 'A' and 'B' are star networks.

Dual Star

Dual-Dual Star: Two individual Dual-Star networks interconnected. Each pair of hubs in the dual star are interconnected, but the interconnected hub pairs are not connected to each other, only the nodes share a connection point between all the hubs.

Fabric Network: Same as a Mesh Topology, Switched Fabric Topology or Fully Connected Topology.

Fully Connected Network: Also called a Fabric Network. A switched-fabric network allows all nodes on the bus to inter-connect with all other nodes on the bus. A network topology in which there is a direct path (branch) between any two nodes. Advanced Switching Interconnect [ASI] is a Switched Fabric network.

Hierarchical Network: A organizational network structure where some number of nodes are subordinate to another node. It's possible for the main nodes to communicate using one protocol or electrical interface while the subordinate or minor nodes use a different protocol.

Hierarchical Network

Hybrid Network: Is a combination of different Topologies. When two or more Topologies are combined within the same network, then its termed a Hybrid Network. Most interfaces will be of the Hybrid type as secondary buses are accounted for. The interface buses that form parts of a Hybrid Topology need not be the same style bus.

Line Network: Also called a Point-to-Point Network, or Linear Network. IEEE-488 is an example of a network that may be connected in a Linear fashion; however GPIB uses the term Daisy Chained. Each piece of equipment in the net uses a dual-face connector that allows the next piece of equipment to daisy chain onto the back of the previous connector forming a chain.

Linear Network: Normally a Point-to-Point Network, as in a 1-Wire Bus, or IC to IC interface.

Loop Network: See Ring Network.

Mesh Network: A network topology in which there are at least two nodes with two or more paths between them. A Mesh Topology is similar to a Fabric Network but more geared to a wireless network. Connections are reconfigured as needed as opposed to being hardwired. Nodes are dropped or added as the need arises, but were never hard-wired as in the case of a Fabric Topology. AdvancedTCA is an example of a Mesh Topology.

Multi-Drop Network: In many cases this refers to one transceiver communicating with some number of receivers on a common bus. The EIA-422 interface [RS422] is an example of an interface network with one driver and some number of multiple receivers all connected on the same interface. A Multi-Drop Network is a specific type of Bus Network Topology.

Multi-Point Network: A Multi-Point interface, unlike a Multi-Drop Network is a topology that allows any node to be a transmitter or receiver. Any node may transmit on a Multi-Point Network [EIA/TIA-485]. A Multi-Point Network is a specific type of Bus Network Topology.

Point-to-Point Network: A single connection interface that connects one device to one other device. A Point-to-Point interface is normally found with IC buses or high speed interconnects with a tight jitter tolerance.

Ring Network: A network topology in which every node has exactly two branches connected to it. A number of interfaces use a ring topology, for example Token Ring. An interface that passed a token [permission to talk] to each node in the ring, one node at a time. A similar topology is the Dual Ring used by the FDDI LAN. See Dual Ring Topology.

Slotted-Ring Network: A ring network that allows unidirectional data transmission between data stations by transferring data in predefined slots in the transmission stream over one transmission medium such that the data return to the originating station.

Star Network: A network topology in which peripheral nodes are connected to a central node, which re-broadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node. IEEE-488 is a classic example of a Star Network having only one possible bus Controller communicating with a number of Talkers and Listeners. Although it's more common to see the IEEE488 [GPIB] interface in a chained [line] configuration, still with only one controller.

Star Topology: An interface configuration that allows all peripheral nodes to communicate with all others by transmitting to, and receiving from, the central node only.

Stubbed Network: Normally a Point-to-Point interconnect with each link connected within a transmission distance away. A Stub Topology will have Signal Reflection issues.

Switched-Fabric Network: Or Fabric Network. A Switched Network allows any device or node to be switched or interconnected to any other device in the network. The InfiniBand interface is interconnected via a Switched-Fabric network.

Tiered Star Topology: Is basically the same as a Compound Star configuration with the host device or computer connected to one star. Each additional star connection is than another tier in the network.

Tree Network: A network topology that, from a purely topological viewpoint, resembles an interconnection of star networks in that individual peripheral nodes are required to transmit to and receive from one other node only, toward a central node, and are not required to act as repeaters or regenerators. The Universal Serial Bus [USB] is a network that uses a Tree Topology. The USB Host Controller is the trunk that branches out to a USB Hub or a USB device. A USB device terminates a branch while a USB Hub may branch out to another Hub or USB device. Each new USB Hub may branch out again until the maximum devices in the network is reached [128].

Twisted Ring Network: Similar to a Ring Topology, but the connection nodes are out of sequence. A Twisted Ring Network might be found being used in a VPX System.

Twisted Ring Network