The McGraw- AS Computing LAN Topologies

The McGraw- Categories of LAN Topology

The McGraw- Bus Topology

The McGraw- Bus Topology Operation

The McGraw- Bus Topology Operation

The McGraw- Advantages & Disadvantages AdvantagesDisadvantages Easy to connect a computer or peripheral to a linear bus. Requires less cable length than a star topology. Entire network shuts down if there is a break in the main cable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shuts down. Not meant to be used as a stand- alone solution in a large building.

The McGraw- Ring Topology

The McGraw- Ring Network advantages The ring topology is specifically designed for use with a LAN and is not suitable for WAN. Its advantages:  There is no dependence on a central host computer as data transmission around the network is supported by all the devices in the ring.  Very high transmission rates are possible; 10 megabits/sec is typical;  Routing between devices is relatively simple because message normally travel in one direction only around the ring;  The transmission facility is shared equally amongst the users.

The McGraw- Ring Network disadvantages  The system depends on the reliability of the whole ring and the repeaters, although it can be designed to bypass any failed node.  It may be difficult to extend the length of the ring because the physical installation of any new cable must ensure that the ring topology is preserved.

The McGraw- Cambridge Ring  It developed at Cambridge University  It has no host computer and none of the nodes need have overall control of access to the network.  Messages in a ring network flow in one direction, from node to node.

The McGraw- Token Ring Network At a start, a free token is circulating on the network, to use the network, a machine first has to capture the free Token and replace the data with its own message.

The McGraw- Star Topology

The McGraw- Star Network advantages  It is suitable for WANs where organisations rely on a central computer for the bulk of processing tasks, perhaps limiting the nodes to their local processing needs and the validation of data, prior to transmission to the central computer.  Centralised control of message switching allows a high degree of security control;  Each spoke in the star is independent of the rest and a fault in a link or device in one spoke, can be identified by the computer at the hub;  The data transmission speeds used cab vary from one spoke to another.

The McGraw- Star Network disadvantages  The network is vulnerable to hub failures which affect all users. As a distributed processing system, some processing is still possible at the nodes but inter-node communication is lost when the host computer fails.  For a WAN, the control of communications in the network required expensive technology at the hub, probably a mini or mainframe computer. Complex operating and communications software is needed to control the network.

The McGraw- Using a Hub in a Star Topology

The McGraw- Using a Switch in a Star Topology

The McGraw- Hybrid Networks Hybrid networks include:  star-bus network  star-ring network  mesh networks

The McGraw- Star / Bus Network Advantages: Point-to-point wiring for individual segments. Supported by several hardware and software vendors. Disadvantages: Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.

The McGraw- Star / Ring network If a single computer fails, it will not affect the rest of the network.

The McGraw- Mesh Network  Each computer is connected to every other computer by a separate cable.  If one computer blows up, it won’t affect the rest of the network.  The big advantage of this topology is its backup capabilities by providing multiple paths through the network.