Mesh, Bus, Ring and Star Topologies
Mesh
A mesh topology typically refers to a Wide Area Network where there are multiple paths connecting multiple sites. A router is used to search multiple paths and determine the best path for the data. Routes are determined by least cost, time of day and performance. A three or four site mesh network is relatively easy to create, whereas it is impractical to set up a mesh network of 100 sites or nodes. Mesh networks are used in Wide Area Networks (WANs) where reliability is important and the number of sites being connected together is fairly small.
A mesh network is costly to reconfigure, replace and administer. A mesh is best suited for situations where it will not need to be moved or expanded beyond five sites or nodes. If one site fails, an entire application can fail. (Bloom, 1998).
Bus
An Ethernet cable usually connects Bus topologies. A bus topology connects your workstations along an open cable length or backbone. If a problem occurs on the backbone, the entire network will go down. Troubleshooting can be difficult, and because data is sent one packet at a time, adding users to the network will slow it down. (Bloom, 1998). Bus topologies are relatively easy to install.
Star
Ethernet cables or Unshielded Twisted Pair (UTP) cables usually connects Star topologies. The star is configured around a central wiring device or switching element, usually an intelligent hub. The hub interprets and routes electrical signals using a high-speed backplane or bus. Each device (workstation, server, etc.) is connected singly to a port on the hub. (Bloom, 1998). Star topologies can be expensive to install, however, quickly identified nodes on the network through the switches, or hubs, will drastically decrease downtime.
Ring
Each workstation on the network is connected to two other workstations, forming a loop or ring. Conflicts in the transmission of data are avoided with token ring technology, which grants messages a "token" or permission to send. Each workstation receives, regenerates and retransmits a token signal until it reaches its destination. (Bloom, 1998).
The variations in connection methods by topology bring about their differences in layout and functionality. A Mesh connects multiple sites unlike any of the other mentioned topologies. A Star topology connects at a central point using an intelligent hub or switch, whereas none of the others utilize a central connection point. The Bus and Ring topologies are most similar in that the nodes on the network are responsible for receiving, regenerating, and retransmitting messages.
“Network topology is the arrangement of the various network elements such as node, link, of computer network. Basically, it is topological structure of a network which ether be physically or logically.”
MAC Layer Connections: Management connections and data transport connections are two connections in this layer. The management connections have three types: basic, primary, and secondary. A basic connection and primary connection are created for each MS when they join the network. A basic connection is used for short and urgent management message. And a primary connection is used for delay-tolerant management messages. The secondary connection is used for IP summarized management messages such as dynamic host configuration protocol [DHCP], and simple network management protocol [SNMP]. Transport connections can be provisioned or can be recognized on demand. They are used for user traffic flows. Unicast or multicast can be used for transmission.
Meanwhile, the advent of early PC’s and the recognition of the value in networking devices together gave rise to Local Area Networks. These LAN’s were developed from a business customer perspective, which placed more emphasis on costs and ease of use over reliability. There were a number of different competing LAN technologies, two of the most common being Token Ring (IBM) and Ethernet (everyone else). The triumph of Ethernet in the marketplace, to the extent where it is included in every PC, game console and some refrigerators, provides a consistent and relatively inexpensive way to build internal networks with relative ease.
Laid out in a line – Has a single cable connecting all of nodes. If one node breaks down the whole network breaks down
Token ring networks had significantly superior performance and reliability compared to early shared-media implementations of Ethernet (IEEE 802.3), and were widely adopted as a higher-performance alternative to shared-media Ethernet.
A switch can be used to make various connections. Ethernet, Token Ring, and various other types of packet switched network segments together to form a heterogeneous network operating at OSI Layer 2.
The Open Systems Interconnection (OSI) reference model is essential to the world of computer networking. The model was created in 1977 by the International Standards Committee, in response to a difficulty that was facing computer networkers at the time (Shelly, Cashman, and Serwatka 142). In order to understand the difficulty, one must first realize that computer networks consist of computer hardware, the software that is to be used in conjunction with this hardware, and the medium (such as wiring or cabling) that will interconnect the computing devices that are in the network. The computer networker’s job is to determine which hardware, software, and medium types will create the network that will best suit his client’s needs. Then, the networker must combine these elements into a functional system of interconnected computers (Fortino and Villeneuve 112). It was in attempting this latter task that the computer networker of the late 1970s often found himself in a pickle. The problem was that each vendor of computing equipment had developed his own unique set of products; products that were incompatible with the products of other vendors. This incompatibility made it very difficult for a computer networker to combine the various network components into an operational computer network (Stamper 27).
Network topologies have some advantages and some disadvantages as well. This essay discusses the main advantages and disadvantages of three of these main topology technologies, to mention, the ring, the bus, and the star, showing the associated wiring types for each one of these topologies.
4. Each computer is connected to a central point, this topology requires a great deal of cable in a large network installation and could cost a great deal of time and money for installation.
In this topology, all nodes are connected to a central device, usually a hub or a switch. Each connected device has a dedicated, point-to-point connection between the device and the hub. The star network topology is by far the most widely implemented topology in use today.
Gateways provide nodes with a contactless connection into the resources that are available for the users. The basic gateways that are installed in many pc are called NIC’s or network interface card (Andrews, 2006, pp. 846-847). These gateways can wither be hardware or protocols within the given equipment that in installed. It is essential that data have the ability to transverse the network. However, to accommodate this function, the data needs to be accepted/rejected and/or forward or dropped. For the purpose of connecting nods, networks, and interaction, gateways must be present. Without any form of implementing gateways, communications would be non-existent. However, the term gateway can also be referred to as routers, wiles AP’s, switches, and hubs. This is fairly easy to distinguish as it points to some form of access to the networks resources.
Networks are designed in a number of ways, based on the geographical area, the technology used, user group specific, application based etc. But we can roughly categorize the communication networks in 2 broad categories, based on transmission: Connection-Oriented and Connectionless.
A Mesh topology is a style of connecting computers in a network in a fashion where every link has a redundant path. A mesh topology is also known as a self healing network in that if a segment of the network fails for what ever reason then the data can still be transmitted across another linked path. This would include possibly hoping across a few extra network segments to reach the destination but it would be able to do it. This redundancy of course comes with a price for the extra pathing that would be incurred to ensure that every node will be able to see every other node.
The term Topology refers to the physical or logical shape or layout of a network. Communication between different nodes within a network is determined by its topology. Mesh, Bus, Ring and Star are four of the most common network topologies, each with advantages and disadvantages in relation to each other.
Network topologies can be classified in to four types. For instant, star topology, ring topology, bus topology and mesh topology.