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A short talk on benefits and disadvantages of two of the most known network topologies.
- Star Topology For Small Business Services
- Star Topology Diagram
- Star Topology Advantage
Jun 11, 2019 Image: Credit For that, you need to first define your small business in a geographical manner because having a small business in the same room is different from having a small business in 3 rooms, situated in 3 different buildings or cities or c. Star topologies are the most common set up in a LAN. This is even more true in a very small LAN such as at your home. This is because you have your single centralized device and all the other devices plug into that single centralized device.
A bus network topology refers to the pattern in which the machines are connected and is one of the simplest ways to connect multiple clients to a network. A bus topology is typically comprised of a pattern consisting of a single link/cable capable of connecting all the network nodes together and thus forming a continual communication line. This is also the reason we call it a bus topology, as its not that different from the bus architecture used in computer motherboards.
Diagram 1 illustrates a typical configuration of a bus topology, in which a set of computers and other network-enabled devices will form a network enabled by a single network cable. In a bus topology, the network communication is achieved by broadcasting packets to all nodes at the same time.
Diagram 1
This is usually done by using a half-duplex twisted-wire that enables communication between computers in both directions, but not simultaneously, only one direction at a time. Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying. [Frequencies, 2016]. When two or more linked computers attempt to communicate on the network simultaneously, it can a cause of one of the biggest problems in a bus topology, the data packet collisions [as shown in Diagram 2]. All bus topologies have this issue. The nodes must employ Medium Access Protocols, which function in conjunction with other nodes, to permit access only at times when the medium us free. [Topologies, routing and deadlock, 2016]
Diagram 2
To overcome and avoid the problem of data transmission collisions, a bus network architecture employs a variety of methods that allow an uninterrupted communication on the bus. One of the ways to prevent the transmission collisions is to use protocols that can control the traffic, one of the most popular is called a CSMA [Carrier Sense Multiple Access] protocol. The main idea behind the CSMA is that protocol controls the traffic and only initiates the data broadcast from each of the nodes, when no other transmission is in progress. If that is not possible, the protocol will wait for a random period [ a typically couple of milliseconds] to try again. In other words, CSMA is based on the principle sense before transmit or listen before talk. Multiple access means that multiple nodes may send and receive on the medium. Transmissions by one node are generally received by all other nodes connected to the medium. [Carrier sense multiple access, 2016]. Carrier Sense Multiple Access protocol also helps to alleviate a problem that can occur during data transmission; a situation called a deadlock. This is the state where two or more computers connected to a bus are jammed from further progressing because each is waiting for a resource that is allocated for one another. A good example is a situation in which a computer and printer are connected to a bus topology network and where the computer is trying to access printer at the same time as the printer is trying to access the computer.
As weve learned, in a bus topology all machines are connected to a shared communication line called a bus. This is different from a star topology in which one computer serves as a central focal point to which all the others are connected. [Brookshear, 2011].
Diagram 3 demonstrates a star topology. As we can see, a central node [typically a hub or switch] provides a common connection point for all nodes. The primary node is acting as a server, whereas all the computer devices are considered clients. The hub and leaf nodes, and the transmission lines between them form a graph with the topology of a star. [Network Topologies, 2012]
Diagram 3
How do bus and star topology differ? The simplest form of explanation is that in a bus topology all communication happens on a single uninterrupted path [network cable], to which all network devices are connected. One good way to visualize this is to imagine a wide road with cars on it. Exits on this road lead to various computers. [Bus and Star Topology, 2006]. It is important to note that a bus topology is no longer very popular, and while there are still valid scenarios for using it, it has been superseded by the star topology, in which all network devices connect directly to a central controlling device [switch, hub, etc.]. Meaning, that any and every communication between computers connected using start topology, has to pass through the switch. The main advantage of the star topology is that deadlocks and bottlenecks do not occur, simply due to a fact that all transmission goes through the hub, which controls the flow of traffic. On the other hand, the primary disadvantage of a star topology is the high dependence of the system on the functioning of the central hub. While the failure of an individual link only results in the isolation of a single node, the failure of the central hub renders the network inoperable, immediately isolating all nodes. [Network Troubleshooting and resource site for school IT staff, 2016].
Following are the two scenarios in which bus or star topology can be used to connect network machines together.
Home Network
A home network is a good use case for using a bus topology. This is because a bus topology is easy to implement and quick to setup, and also simple to later extend. That makes it an appropriate choice for small home networks. Due to a nature of a bus network where all computers share a single cable, a bus network is also cheaper to deploy than other network topologies. In a bus topology, its also easier to debug issues, such as faulty network cables, etc.
Office Network
A small business office network is an excellent use case for a star network topology. In this type of networking, non-centralized network catastrophes will pose a tiny negative impact on the system and thus a little effect on business functioning. This topology is easy to understand, and the isolation and centralization allow for a simple detection of errors. One of the major benefits for a business implementation is a fact that new nodes can be easily added to a network, without any impact to other devices. As far as cons go, following drawbacks of star topology are crucial to mention. First, its more expensive to implement, as each machine needs its own dedicated line to a central switch. Secondly, the central node is a single point of failure [Star network, 2016], if the central switch fails, the whole network goes down. Most businesses alleviated the problem of a central failure by keeping the replacement switch.
References
Brookshear, G. [2011] Computer science an overview [11th 2011]. Available at: //www.academia.edu/20063137/_Computer_Science_An_Overview._11th_2011_.J_Glenn_Brookshear [Accessed: 3 September 2016].
Star Topology For Small Business Services
Network Topologies [2012] Available at: //lar-bear.weebly.com/network-topologies.html [Accessed: 3 September 2016].
D.B., lengkapku, L. profil and vio, faris [2073] Devy Blog. Available at: //devytamala.blogspot.ca/2012/03/network-topology-that-uses-common.html [Accessed: 3 September 2016].
Bus network [2016] in Wikipedia. Available at: //en.wikipedia.org/wiki/Bus_network [Accessed: 3 September 2016].
Frequencies [2016] Duplex [telecommunications], in Wikipedia. Available at: //en.wikipedia.org/wiki/Duplex_[telecommunications]#HALF-DUPLEX [Accessed: 3 September 2016].
Topologies, routing and deadlock [2016] Available at: //www.powershow.com/view/1304e1-ZmVmM/Topologies_Routing_and_Deadlock_powerpoint_ppt_presentation [Accessed: 3 September 2016].
Carrier sense multiple access [2016] in Wikipedia. Available at: //en.wikipedia.org/wiki/Carrier_sense_multiple_access [Accessed: 3 September 2016].
Bus and Star Topology [2006], Explain the differences between Bus and Star Topology, Available at: //answers.yahoo.com/question/index?qid=20061114214751AAIL4gf [Accessed: 4 September 2016].
Network Troubleshooting and resource site for school IT staff [2016] Available at: //webpage.pace.edu/ms16182p/networking/star.html [Accessed: 4 September 2016].
Star network [2016] in Wikipedia. Available at: //en.wikipedia.org/wiki/Star_network [Accessed: 5 September 2016].
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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 used to pass information between work stations.
Source: ResearchGate
Main Types of Network Topologies
In networking, the term 'topology' refers to the layout of connected devices on a network. There are several different types of network topology. 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 family room circle, but it would be highly unlikely to find an actual ring topology there.
Network topologies are categorized into the following basic types. And more complex networks can be built as hybrids of two or more of the underlying topologies.
1. 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 center 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 whole network also fails.]
See the illustration of Star Network Topology.
Advantages of a Star Topology
- Easy to install and wire.
- No disruptions to the network were then connecting or removing devices.
- Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
- It 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.
The protocols used with star configurations are usually Ethernet or LocalTalk. Token Ring uses a similar topology, called the star-wired ring.
Star-Wired Ring
A star-wired ring topology may appear [externally] to be the same as a star topology. Internally, the MAU of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring [see fig. 3]. The Token Ring protocol uses a star-wired ring topology.
2. 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.
See the illustration of Ring Topology.
3. 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. Still, only the intended recipient 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. Also, if the backbone cable fails, the entire network effectively becomes unusable.
See the illustration of Bus Network Topology.
Advantages of a Linear Bus Topology
- Easy to connect a computer or peripheral to a linear bus.
- It requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
- The 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.
4. Tree Topology
Tree topologies integrate multiple star topologies onto a bus. In its purest 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 the network's future expandability much better than a bus [limited in the number of devices due to the broadcast traffic it generates] or a star [defined by the number of hub connection points] alone.
See the illustration of Tree Network Topology.
Advantages of a Tree Topology
- Point-to-point wiring for individual segments.
- Supported by hardware and software venders.
Disadvantages of a Tree Topology
- The 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.
5. 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.
Star Topology Diagram
See the illustration of Mesh Network Topology.
6. Hybrid Topology
A combination of any two or more network topologies. Note 1: Instances can occur where two basic network topologies, when connected, can still retain the basic network character, and therefore not be a hybrid network. For example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues only when two basic networks are connected, and the resulting network topology fails to meet one of the basic topology definitions. For example, two-star networks connected exhibit hybrid network topologies. Note 2: A hybrid topology always accrues when two different basic network topologies are connected.
5-4-3 Rule
A consideration in setting up a tree topology using Ethernet protocol is the 5-4-3 rule. One aspect of the Ethernet protocol requires that a signal sent out on the network cable reaches every part of the network within a specified time. Each concentrator or repeater that a message goes through adds a small amount of time. It leads to the rule that there can only be a maximum of 5 segments between any two nodes on the network, connected through 4 repeaters/concentrators. Also, only 3 of the parts may be populated [trunk] segments if they are made of coaxial cable. A populated section is one that has one or more nodes attached to it. In Figure 4, the 5-4-3 rule adheres to each other. The furthest two nodes on the network have four segments and three repeaters/concentrators between them.
This rule does not apply to other network protocols or Ethernet networks where all fiber optic cabling or a combination of a fiber backbone with UTP cabling is used. If there is a combination of fiber optic backbone and UTP cabling, it is simply translated to 7-6-5 rule.
Considerations When Choosing a Topology
- Money. A linear bus network may be the least expensive way to install a network; you do not have to purchase concentrators.
- Length of cable needed. The linear bus network uses shorter lengths of cable.
- Future growth. With a star topology, expanding a network is easily done by adding another concentrator.
- Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologies.
Other Definition of Network Topology
A network consists of multiple computers connected using some interface. Each has one or more interface devices such as a Network Interface Card [NIC] and 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 this document is the 10Base-T category 5 Ethernet cable. It 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.
In a server-based network, there are computers set up to be primary providers of services such as file service or mail service. The machines providing the service are called servers, and the computers that request and use the service are called client computers.
In a peer-to-peer network, various computers on the network can act both as clients and servers. For instance, many Microsoft Windows-based computers will allow file and print sharing. These computers can work both as clients and servers and are also referred to as peers. Many networks are a combination of peer-to-peer and server-based networks. The network operating system uses a network data protocol to communicate on the net to other computers. The network operating system supports the applications on that computer. A Network Operating System [NOS] includes Windows NT, Novell Netware, Linux, Unix, and others.
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Star Topology Advantage
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