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Appendix 1

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verickle's version from 2016-11-01 19:51

Characteristics, Benefits, and Drawbacks of a Bus Topology

CharacteristicsBenefitsDrawbacks
One cable is used per network segment.Less cable is required to install a bus topology, as compared with other topologies.Because a single cable is used per network segment, the cable becomes a potential single point of failure.
To maintain appropriate electrical characteristics of the cable, the cable requires a terminator (of a specific resistance) at each end of the cable.Depending on the media used by the bus, a bus topology can be less expensive.Troubleshooting a bus topology can be difficult because problem isolation might necessitate an inspection of multiple network taps to make sure they either have a device connected or they are properly terminated.
Bus topologies were popular in early Ethernet networks.Installation of a network based on a bus topology is easier than some other topologies, which might require extra wiring to be installed.Adding devices to a bus might cause an outage for other users on the bus.
Network components tap directly into the cable via a connector such as a T connector or a vampire tap.An error condition existing on one device on the bus can impact performance of other devices on the bus.
A bus topology does not scale well because all devices share the bandwidth available on the bus. Also, if two devices on the bus simultaneously request access to the bus, an error condition results.
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Characteristics, Benefits, and Drawbacks of a Ring Topology

CharacteristicsBenefitsDrawbacks
Devices are interconnected by connecting to a single ring or, in some cases (for example, FDDI), a dual ring.A dual ring topology adds a layer of fault tolerance. Therefore, if a cable break occurred, connectivity to all devices could be restored.A break in a ring when a single ring topology is used results in a network outage for all devices connected to the ring.
Each device on a ring includes both a receiver (for the incoming cable) and a transmitter (for outgoing cable).Troubleshooting is simplified in the event of a cable break, because each device on a ring contains a repeater. When the repeater on the far side of a cable break does not receive any data within a certain amount of time, it reports an error condition (typically in the form of an indicator light on a network interface card [NIC]).Rings have scalability limitations. Specifically, a ring has a maximum length and a maximum number of attached stations. Once either of these limits is exceeded, a single ring might need to be divided into two interconnected rings. A network maintenance window might need to be scheduled to perform this ring division.
Each device on the ring repeats the signal it receives.Because a ring must be a complete loop, the amount of cable required for a ring is usually higher than the amount of cable required for a bus topology serving the same number of devices.
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Characteristics, Benefits, and Drawbacks of a Star Topology

CharacteristicsBenefitsDrawbacks
Devices have independent connections back to a central device (for example, a hub or a switch).A cable break only impacts the device connected via the broken cable, and not the entire topology.More cable is required for a star topology, as opposed to bus or ring topologies because each device requires its own cable to connect back to the central device.
Star topologies are commonly used with Ethernet technologies (described in Lesson 4).Troubleshooting is relatively simple because a central device in the star topology acts as the aggregation point of all the connected devices.Installation can take longer for a star topology, as opposed to a bus or ring topology, because more cable runs that must be installed.
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Characteristics, Benefits, and Drawbacks of a Hub-and-Spoke Topology

CharacteristicsBenefitsDrawbacks
Each remote site (that is, a spoke) connects back to a main site (that is, the hub) via a WAN link.Costs are reduced (as compared to a full-mesh or partial-mesh topology) because a minimal number of links is used.Suboptimal routes must be used between remote sites because all inter-site communication must travel via the main site.
Communication between two remote sites travels through the hub site.Adding one or more additional sites is easy (as compared to a full-mesh or partial-mesh topology) because only one link needs to be added per site.Because all remote sites converge on the main site, this hub site potentially becomes a single point of failure.
Because each remote site is reachable by only a single WAN link, the hub-and-spoke topology lacks redundancy.
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Characteristics, Benefits, and Drawbacks of a Full-Mesh Topology

CharacteristicsBenefitsDrawbacks
Every site has a direct WAN connection to every other site.An optimal route exists between any two sites.A full-mesh network can be difficult and expensive to scale, because the addition of one new site requires a new WAN link between the new site and every other existing site.
The number of required WAN connections can be calculated with the formula w = n * (n – 1) / 2, where w = the number of WAN links and n = the number of sites. For example, a network with 10 sites would require 45 WAN connections to form a fully meshed network: 45 = 10 * (10 – 1) / 2.A full-mesh network is fault tolerant because one or more links can be lost and reachability between all sites might still be maintained.
Troubleshooting a full-mesh network is relatively easy because each link is independent of the other links.
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Characteristics, Benefits, and Drawbacks of a Partial-Mesh Topology

CharacteristicsBenefitsDrawbacks
Selected sites (that is, sites with frequent inter-site communication) are interconnected via direct links, whereas sites that have less-frequent communication can communicate via another site.A partial-mesh topology provides optimal routes between selected sites with higher inter-site traffic volumes, while avoiding the expense of interconnecting every site to every other site.A partial-mesh topology is less fault tolerance than a full-mesh topology.
A partial-mesh topology uses fewer links than a full-mesh topology and more links than a hub-and-spoke topology for interconnecting the same number of sites.A partial-mesh topology is more redundant than a hub-and-spoke topology.A partial-mesh topology is more expensive than a hub-and-spoke topology.
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Characteristics, Benefits, and Drawbacks of a Client/Server Network

CharacteristicsBenefitsDrawbacks
Client devices (for example, PCs) share a common set of resources (for example, file or print resources) located on one or more dedicated servers.Client/server networks can easily scale, which might require the purchase of additional client licenses.Because multiple clients might rely on a single server for their resources, the single server can become a single point of failure in the network
Resource sharing is made possible via dedicated server hardware and network operating systems.Administration is simplified, because parameters, such as file sharing permissions and other security settings, can be administered on a server as opposed to multiple clients.Client/server networks can cost more than peer-to-peer networks. For example, client/server networks might require the purchase of dedicated server hardware and a network OS with an appropriate number of licenses.
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Characteristics, Benefits, and Drawbacks of a Peer-to-Peer Network

CharacteristicsBenefitsDrawbacks
Client devices (for example, PCs) share their resources (for example, file and printer resources) with other client devices.Peer-to-peer networks can be installed easily because resource sharing is made possible by the clients' operating systems, and knowledge of advanced NOSs is not required.Scalability is limited because of the increased administration burden of managing multiple clients.
Resource sharing is made available through the clients' operating systems.Peer-to-peer networks usually cost less than client/server networks because there is no requirement for dedicated server resources or advanced NOS software.Performance might be less than that seen in a client/server network because the devices providing network resource might be performing other tasks not related to resource sharing (for example, word processing).
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