Chapter 6…………

Topologies in networking

A network topology is the geometric arrangement of nodes and cable links in a LAN, thats what we learn in the class...need 2 find 2 more types of topologys...MESH n TREE

There are three topology’s to think about when you get into networks. These are the star, ring, and the bus.
Star - a ring topology features a logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater, meaning it regenerates the signal
Ring - in a star topology each node has a dedicated set of wires connecting it to a central network hub. Since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics.
Bus - the bus topology, each node (computer, server, peripheral etc.) attaches directly to a common cable. This topology most often serves as the backbone for a network. In some instances, such as in classrooms or labs, a bus will connect small workgroups

MESH TOPOLOGY
A type of network setup where each of the computers and network devices are interconnected with one another, allowing for most transmissions to be distributed, even if one of the connections go down. This type of topology is not commonly used for most computer networks as it is difficult and expensive to have redundant connection to every computer. However, this type of topology is commonly used for wireless networks. Below is a visual example of a simple computer setup on a network using a mesh topology.


TREE TOPOLOGY

Among all the Network Topologies we can derive that the Tree Topology is a combination of the bus and the Star Topology. The tree like structure allows you to have many servers on the network and you can branch out the network in many ways. This is particularly helpful for colleges, universities and schools so that each of the branches can identify the relevant systems in their own network and yet connect to the big network in some way.

NETWORKING CABLE 2...PRO'S N CON'S
Types of Networking Cables:

The three main types of networking cables are coaxial cable, twisted-pair cable and fiber optic cable and the differences................

Coaxial Cable:

Coaxial cable is made of two conductors that share the same axis; the center is a copper wire that is insulated by a plastic coating and then wrapped with an outer conductor (usually a wire braid). This outer conductor around the insulation serves as electrical shielding for the signal being carried by the inner conductor. A tough insulating plastic tube outside the outer conductor provides physical and electrical protection. At one time, coaxial cable was the most widely used network cabling. However, with improvements and the lower cost of twisted-pair cables, it has lost its popularity.

Network Cable Types

There are two types of coaxial cable.

1. ThickNet
2. ThinNet

ThickNet:

ThickNet is about .38 inches in diameter. This makes it a better conductor, and it can carry a signal about 1640 feet (500 meters) before signal strength begins to suffer. The disadvantage of ThickNet over ThinNet is that it is more difficult to work with. The ThickNet version is also known as standard Ethernet cable.

ThinNet:

ThinNet is the easiest to use. It is about .25 inches in diameter, making it flexible and easy to work with (it is similar to the material commonly used for cable TV). ThinNet can carry a signal about 605 feet (185 meters) before signal strength begins to suffer.


Twisted-Pair Cable:

Twisted-pair cable consists of two insulated strands of copper wire twisted around each other to form a pair. One or more twisted pairs are used in a twisted-pair cable. The purpose of twisting the wires is to eliminate electrical interference from other wires and outside sources such as motors. Twisting the wires cancels any electrical noise from the adjacent pair. The more twists per linear foot, the greater the effect.

Network Cable Types

There are two types of twisted pair cable

1. Shielded Twisted Pair (STP)

2. Unshielded Twisted Pair (UTP)

Shielded Twisted Pair (STP):

The only difference between STP and UTP is that STP has a foil or wire braid wrapped around the individual wires of the pairs. The shielding is designed to minimize EMI radiation and susceptibility to crosstalk. The STP cable uses a woven-copper braided jacket, which is a higher-quality, more protective jacket than UTP.

Unshielded Twisted Pair (UTP):

As the name implies, "unshielded twisted pair" (UTP) cabling is twisted pair cabling that contains no shielding. UTP cables can be divided further into following categories:
Category 1 : Traditional telephone cable. Carries voice but not data
Category 2 : Certified UTP for data transmission of up to 4 megabits per second (Mbps). It has four twisted pairs
Category 3 : Certified UTP for data transmission of up to 10 Mbps. It has four twisted pairs
Category 4 : Certified UTP for data transmission of up to 16 Mbps. It has four twisted pairs
Category 5 : Certified for data transmission of up to 100 Mbps. It has four twisted pairs of copper wire
Category 6 :Offers transmission speeds up to 155 Mbps
Category 7 :Category 7 is a proposed standard that aims to support transmission at frequencies up to 600 MHz

Twisted-pair cable has several advantages over other types of cable (coaxial and fiberoptic): It is readily available, easy to install, and inexpensive. Among its disadvantages are its sensitivity to electromagnetic interference (EMI), its susceptibility to eavesdropping, its lack of support for communication at distances of greater than 100 feet, and its requirement of a hub (multiple network connection point) if it is to be used with more than two computers. Twisted pair cables use RJ45 connector.

Unshielded Twisted Pair (UTP)
This is the most popular form of cables in the network and the cheapest form that you can go with. The UTP has four pairs of wires and all inside plastic sheathing. The biggest reason that we call it Twisted Pair is to protect the wires from interference from themselves. Each wire is only protected with a thin plastic sheath.

Shielded Twisted Pair (STP)
Is more common in high-speed networks. The biggest difference you will see in the UTP and STP is that the STP use’s metallic shield wrapping to protect the wire from interference.
-Something else to note about these cables is that they are defined in numbers also. The bigger the number the better the protection from interference. Most networks should go with no less than a CAT 3 and CAT 5 is most recommended.
-Now you know about cables we need to know about connectors. This is pretty important and you will most likely need the RJ-45 connector. This is the cousin of the phone jack connector and looks real similar with the exception that the RJ-45 is bigger. Most commonly your connector are in two flavors and this is BNC (Bayonet Naur Connector) used in thicknets and the RJ-45 used in smaller networks using UTP/STP.