DIFFERENT NETWORK TOPOLOGIES

DIFFERENT NETWORK TOPOLOGIES

Network Topology is the specific physical, logical, or virtual, arrangement of the network components and devices (nodes). Network topology is determined only by the configuration of connections between nodes. Distances between nodes, physical interconnections, transmission rates, and/or signal types are not effects in a network topology. The common types of network topology are described below.
Bus topology or Linear Topology: All nodes on the LAN are connected by one linear cable, which is called the shared medium. Every node on this cable segment sees transmissions from every other station on the same segment. At each end of the bus is a terminator, which absorbs any signal, removing it from the bus. This medium cable apparently is the single point of failure. Ethernet (IEEE 802.3) is the protocols used for this type of LAN.
Mesh topology: Devices are connected with many redundant interconnections between network nodes such as routers and switches. In a mesh topology if any cable or node fails, there are many other ways for two nodes to communicate. Full mesh topology occurs when every node has a circuit connecting it to every other node in a network. Partial mesh topology where some nodes are organized in a full mesh scheme but others are only connected to one or two in the network, is often used in real network to provide the reliability with less complexity.
Ring topology: Every network node has two branches connected to it and form a ring. If one of the nodes on the ring fails than the ring is broken and cannot work. A dual ring topology has four branches connected to it, and is more resistant to failures.
Star topology: The network nodes are connected to a central node, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only.
Tree topology: The network nodes are arranged as a tree, which resembles an interconnection of star networks in that individual peripheral nodes are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the function of the central node may be distributed.
A hybrid topology is a combination of any two or more network topologies in such a way that the resulting network does not have one of the standard forms. For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit hybrid network topologies. A hybrid topology is always produced when two different basic network topologies are connected.

UTP
Short for unshielded twisted pair, a popular type of cable that consists of two unshielded wires twisted around each other. Due to its low cost, UTP cabling is used extensively for local-area networks (LANs) and telephone connections. UTP cabling does not offer as high bandwidth or as good protection from interference as coaxial or fiber optic cables, but it is less expensive and easier to work with.

STP
Often abbreviated STP, a type of copper telephone wiring in which each of the two copper wires that are twisted together are coated with an insulating coating that functions as a ground for the wires. The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference leaking into or out of the cable. STP cabling often is used in Ethernet networks, especially fast data rate Ethernets.

Fiber Optical Networks
Spawned by the fiber-optic cable technologies in the early 80's, optical networks provide a high-capacity telecommunications network based on fiber optical technologies. Optical networks address increasing bandwidth issues as well as provide a higher capacity and reduce overall costs. The first digital networks were asynchronous networks. Asynchronous is usually used to describe communications in which data can be transmitted intermittently rather than in a steady stream. As optical became more of a popular technology choice, the need for standards lead to the creation of the synchronous optical network (SONET), where SONET provided standards for line rates, coding, operations, and defined the types of network elements required.What Is Fiber Optics Technology? Fiber optics is a technology that uses glass (or plastic) threads, called fibers to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. Over metal cables, fiber optics provide a much greater bandwidth to carry more data, they are are less susceptible than metal cables to interference, they are thinner and lighter than metal wires, and most importantly data can be transmitted digitally (the natural form for computer data) through the use of fiber optics. Like all technologies, fiber optics has its downside. The cost of fiber optic cable is more than metal cable, making the cost for installation much greater. In addition they are more fragile than wire and are difficult to split. Fiber optics is a particularly popular technology for local-area networks. Telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.

Cable Type Data Capacity Length Connection Type

Fiber Optic 100Mbps-1Gbps 2,000 Meters ST, SC, & SMA

Fiber optic Connector
Twisted Pair:
Unshielded (UTP) 10-100Mbps 100 Meters RJ-45 IBM
Shielded (STP) 10-100Mbps 500 Meters DataConnector

Firewire 400 Mbps 700 meters

Advantage and disadvantages

UTP – 10 –100Mbps and only 100 meters maximum length
STP – 10 – 100 Mbps and has 500 meters maximum length
Firewire – 400 Mbps and has 700 meters and above
Fiber Optic cables - 100Mbps-1Gbps and has 2,000 Meters and above maximum length

ETHERNET CABLE: COLOR-CODE STANDARDS

The information listed here is to assist Network Administrators in the color coding of Ethernet cables. Please be aware that modifying Ethernet cables improperly may cause loss of network connectivity. Use this information at your own risk, and insure all connectors and cables are modified in accordance with standards. The Internet Centre and its affiliates cannot be held liable for the use of this information in whole or in part.

T-568A Straight-Through Ethernet Cable

The TIA/EIA 568-A standard which was ratified in 1995, was replaced by the TIA/EIA 568-B standard in 2002 and has been updated since. Both standards define the T-568A and T-568B pin-outs for using Unshielded Twisted Pair cable and RJ-45 connectors for Ethernet connectivity. The standards and pin-out specification appear to be related and interchangeable, but are not the same and should not be used interchangeably.

RJ-45 Crossover Ethernet Cable

A good way of remembering how to wire a Crossover Ethernet cable is to wire one end using the T-568A standard and the other end using the T-568B standard. Another way of remembering the color coding is to simply switch the Green set of wires in place with the Orange set of wires. Specifically, switch the solid Green (G) with the solid Orange, and switch the green/white with the orange/white.

WI-FI

Wi-Fi was originally a brand licensed by the Wi-Fi Alliance to describe the embedded technology of wireless local area networks (WLAN) based on the IEEE 802.11 standard. As of 2007, common use of the term Wi-Fi has broadened to describe the generic wireless interface of mobile computing devices, such as laptops in LANs.[citation needed] The term Wi-Fi was chosen as a play on the term "Hi-Fi", and is often thought to be an abbreviation for wireless fidelity, though the Wi-Fi Alliance no longer recognizes such. Wi-Fi and the Wi-Fi CERTIFIED logo are registered trademarks of the Wi-Fi Alliance, the trade organization that tests and certifies equipment compliance with the 802.11 standards.
Common uses for Wi-Fi include Internet and VoIP phone access, gaming, and network connectivity for consumer electronics such as televisions, DVD players, and digital cameras. In spite of media reports about possible health risks from Wi-Fi, scientific studies have failed to show a causal effect