A bus network is a network topology in which nodes are directly connected to a common linear (or branched) half-duplex link called a bus.

Function

A host on a bus network is called a Station or workstation. In a bus network, every station will receive all network traffic, and the traffic generated by each station has equal transmission priority.A bus network forms a single network segment and collision domain. In order for nodes to transmit on the same bus simultaneously, they use a media access control technology such as carrier sense multiple access (CSMA) or a bus master.

If any link or segment of the bus is severed, all network transmission ceases due to signal bounce caused by the lack of a terminating resistor.

Advantages and disadvantages

Advantages

-Very easy to connect a computer or peripheral to a linear bus

-Requires less cable length than a star topology resulting in lower costs

-It works well for small networks.

-It is easy to extend by joining cable with connector or repeater.

Disadvantages

-Entire network shuts down if there is a break in the main cable or one of the T connectors break.

-Large amount of packet collisions on the network, which results in high amounts of packet loss.

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 SONET/SDH). 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. 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 Spatial Reuse Protocol, Fiber Distributed Data Interface (FDDI), and Resilient Packet Ring. 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.

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.

Advantages

• ·         Very orderly network where every device has access to the token and the opportunity to transmit

• Performs better than a bus topology under heavy network loa

• Does not require a central node to manage the connectivity between the computers

• Due to the point to point line configuration of devices with a device on either side (each device is connected to its immediate neighbor), it is quite easy to install and reconfigure since adding or removing a device requires moving just two connection

• Point to point line configuration makes it easy to identify and isolate faults.

• Reconfiguration for line faults of bidirectional rings can be very fast, as switching happens at a high level, and thus the traffic does not require individual rerouting.

Disadvantages

• One malfunctioning workstation can create problems for the entire network. This can be solved by using a dual ring or a switch that closes off the break.

• Moving, adding and changing the devices can affect the network

• Communication delay is directly proportional to number of nodes in the network

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central hub which acts as a conduit to transmit messages. In star topology, every host is connected to a central hub.

A star network is an implementation of a spoke–hub distribution paradigm in computer networks. Thus, the hub and leaf nodes, and the transmission lines between them, form a graph with the topology of a star. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable and optical fibre cable. However, it can also be used with coaxial cable.

The star topology reduces the impact of a line failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub re-broadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected