Network topologies
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The document discusses various network topologies including star, ring, bus, tree, mesh, and hybrid topologies. A star topology features a central hub with devices connecting to the hub. A ring topology uses a closed loop where devices are connected in a continuous path. A bus topology uses a shared backbone that devices tap into to communicate. A tree topology combines star topologies onto a bus. A mesh topology allows messages to take multiple paths between devices.
Network topologies
- 1. Abdul Salam Shaikh BBA (Final) Evening. Roll# 105. NETWORK TOPOLOGIES & IT’S TYPES What is Network Topology The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter. A network consists of multiple computers connected using some type of interface, each having one or more interface devices such as a Network Interface Card (NIC) and/or a serial device for PPP networking. Each computer is supported by network software that provides the server or client functionality. The hardware used to transmit data across the network is called the media. It may include copper cable, fiber optic, or wireless transmission. The standard cabling used for the purposes of this document is 10Base-T category 5 Ethernet cable. This is twisted copper cabling which appears at the surface to look similar to TV coaxial cable. It is terminated on each end by a connector that looks much like a phone connector. Its maximum segment length is 100 meters. Main Types of Network Topologies In networking, the term "topology" refers to the layout of connected devices on a network. This article introduces the standard topologies of computer networking. One can think of a topology as a network's virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find an actual ring topology there. Network topologies are categorized into the following basic types: • Star Topology • Ring Topology • Bus Topology • Tree Topology • Mesh Topology • Hybrid Topology
- 2. Star Topology Many home networks use the star topology. A star network features a central connection point called a "hub" that may be a hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet. Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.) Advantages of a Star Topology • Easy to install and wire. • No disruptions to the network then connecting or removing devices. • Easy to detect faults and to remove parts. Disadvantages of a Star Topology • Requires more cable length than a linear topology. • If the hub or concentrator fails, nodes attached are disabled. • More expensive than linear bus topologies because of the cost of the concentrators. Ring Topology In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses. Bus Topology Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message. Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives. 10Base-2 ("ThinNet") and 10Base-5 ("ThickNet") both were popular Ethernet cabling options many years ago for bus topologies. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.
- 3. Advantages of a Bus Topology • Easy to connect a computer or peripheral to a linear bus. • Requires less cable length than a star topology. Disadvantages of a Bus 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. Tree Topology Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone. Advantages of a Tree Topology • Point-to-point wiring for individual segments. • Supported by several hardware and software venders. Disadvantages of a Tree Topology • 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. Mesh Topology Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing. A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others.