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most used topology

Bus: This topology allows all stations to receive the information that is transmitted, one station transmits and all other stations listen. It consists of a cable with a terminator at each end of which all the elements of a network are hung. All the nodes of the network are connected to this cable: which is called "Backbone Cable". Both Ethernet and Local Talk can use this topology.

The bus is passive, there is no regeneration of the signals in each node. The nodes in a "bus" network transmit the information and hope that it will not collide with other information transmitted by another of the nodes. If this occurs, each node waits a small amount of random time, then tries to relay the information.

Ring: The stations are connected to each other forming a circle by means of a common cable. The last node of the chain is connected to the first one by closing the ring. The signals circulate in only one direction around the circle, regenerating at each node. With this methodology, each node examines the information that is sent through the ring. If the information is not directed to the node that examines it, pass it to the next one in the ring. The disadvantage of the ring is that if a connection is broken, the entire network goes down

Star: The data in these networks flows from the sender to the concentrator, it performs all the functions of the network, also acts as an amplifier of the data.

The network joins at a single point, usually with a centralized control panel, such as a wiring hub. The information blocks are directed through the central control panel to their destinations. This scheme has an advantage by having a control panel that monitors traffic and prevents collisions and an interrupted connection does not affect the rest of the network

Hybrids: The linear bus, the star and the ring combine sometimes to form combinations of hybrid networks
Star Ring: This topology is used in order to facilitate network administration. Physically, the network is a centralized star in a hub, while at the logical level, the network is a ring.

"Bus" in Star: The end is equal to the previous topology. In this case the network is a "bus" that is physically wired as a star through hubs.

Hierarchical Star: This wiring structure is used in most current local networks, through cascading hubs to form a hierarchical network

Tree: This structure is used in cable television applications, on which future network structures that reach homes could be based. It has also been used in analog local broadband network applications.

Plot: This network structure is typical of WANs, but can also be used in some local network (LAN) applications. Workstations are connected to each other.

The three most used topologies are:

Central Link Network: It is generally found in office or field environments, in which the networks of the floors of a building are interconnected over central cables. Bridges and routers manage traffic between connected network segments.

Mesh Network: This involves or is done through WAN networks, a mesh network contains multiple paths, if a path fails or traffic is congested, a packet can use a different path to the destination. Routers are used to interconnect separate networks.

Hierarchical Star Network: This wiring structure is used in most of the current local networks, through cascaded hubs to form a hierarchical network

Network Topology

The network topology or logical network form is defined as the communication chain that the nodes that make up a network use to communicate. It is the geometric distribution of connected computers

Bus network

Network whose topology is characterized by having a single communications channel (called bus, trunk or backbone) to which the different devices are connected. In this way all devices share the same channel to communicate with each other.
The bus topology has all its nodes connected directly to a link and has no other connection to each other. Physically each host is connected to a common cable, so they can communicate directly. The cable break causes the hosts to be disconnected.

The ends of the cable are terminated with a coupling resistor called terminator, which in addition to indicating that there are no more computers at the end, allow the bus to be closed by means of an impedance coupling.

It is the third of the main topologies. The stations are connected by a single cable segment. Unlike a ring network, the bus is passive, there is no signal generation at each node.

Advantage

Ease of deployment and growth.
Economic.
Simplicity in architecture.

Disadvantages

Limited channel lengths.
A problem in the channel usually degrades the entire network.
Performance decreases as the network grows.
The channel needs to be properly closed (closed roads).
High transmission losses due to collisions between messages

STAR NETWORK

A star network is a network in which the stations are directly connected to a central point and all the communications that must necessarily be made through it.
Given its transmission, an active star network has an active central node that normally has the means to prevent echo related problems.

It is used mostly for local networks. Most local area networks that have a router, a switch, or a hub follow this topology. The central node in these would be the router, the switch or the hub, through which all packets pass.

Advantage

It has two means to prevent problems.
It allows all nodes to communicate with each other conveniently.

Disadvantages

If the central node fails, the entire network is disconnected.
It is expensive, since it requires more cable than the Bus and Ring topology.
The cable travels separately from the hub to each computer

Ring network

Network topology in which each station is connected to the next and the last is connected to the first. Each station has a receiver and a transmitter that acts as a repeater, passing the signal to the next station.

In this type of network the communication is given by the passage of a token or witness, which can be conceptualized as a mailman who passes collecting and delivering information packages, thus avoiding possible loss of information due to collisions.

It is worth mentioning that if any node in the network stops working, communication throughout the ring is lost.

In a double ring, two rings allow data to be sent in both directions. This configuration creates redundancy (fault tolerance), which means that if one of the rings fails, the data can be transmitted by the other.

Advantage

· Simplicity of architecture. Ease of implesion and growth.

Disadvantages [edit]

· Limited channel lengths.
· The channel will usually degrade as the network grows.

Mesh network

The mesh topology is a network topology in which each node is connected to all nodes. In this way it is possible to take messages from one node to another by different paths. If the mesh network is completely connected, there can be absolutely no interruption in communications. Each server has its own connections with all other servers.


The establishment of a mesh network is a way to route data, voice and instructions between nodes. Mesh networks differ from other networks in that the elements of the network (node) are all connected to all, by separate cables. This configuration offers redundant paths throughout the network so that, if one cable fails, another will take care of the traffic.


This topology, unlike others (such as tree topology and star topology), does not require a central server or node, which reduces maintenance (an error in a node, whether important or not, does not imply the fall of the entire network).


Mesh networks are auto routable. The network can work, even when a node disappears or the connection fails, since the rest of the nodes avoid passing through that point. Consequently, the mesh network is transformed into a very reliable network.


It is an option applicable to wireless networks (Wireless), wired networks (Wired) and node software interaction.


A network with mesh topology offers superior redundancy and reliability. Although the ease of troubleshooting and increasing reliability are very interesting advantages, these networks are expensive to install, since they use a lot of wiring. Therefore, they become more important in the use of wireless networks (due to the lack of wiring) despite the inconveniences of Wireless.


In many cases, the mesh topology is used together with other topologies to form a hybrid topology. It is connected to a server that sends other computers
A mesh network effectively extends a network, sharing access to a larger infrastructure.

Tree network

Network topology in which the nodes are placed in the form of a tree. From a topological view, the tree connection is similar to a series of interconnected star networks except that it does not have a central node. Instead, it has a trunk link node, usually occupied by a hub or switch, from which the other nodes branch. It is a variation of the bus network, the failure of a node does not imply interruption in communications. The same communications channel is shared.

The tree topology can be seen as a combination of several star topologies. Both the tree and the star are similar to the bus when the interconnection node works in broadcast mode, since the information is propagated to all stations, only in this topology the branches extend from a root point ( star), as many branches as possible, depending on the characteristics of the tree.

types of network cables

MAIN TYPES OF CABLES

The vast majority of networks are connected by some type of wiring, which acts as a means of transmission where the signals pass between the equipment. A large number of cable types are available to meet the needs and sizes of different networks, from the smallest to the largest.

There are a lot of types of cables. Some manufacturers publish a catalog with more than 2000 different types that can be grouped into 3 groups:

COAXIAL CABLE

 

A coaxial cable consists of a core of copper wire surrounded by an insulator, a braided metal shield and an outer sheath. The term shielding refers to the braided or metal mesh that surrounds some types of cable. The shield protects the transmitted data by absorbing spurious electronic signals, called noise, so that they do not pass through the cable and do not distort the data. The cable containing an insulating sheet and a braided metal shielding layer is called a double shielded cable. For environments that are subject to large interference, a quadruple shield is available. This shield consists of two insulating sheets and 2 layers of braided metal shielding.


TYPES OF COAXIAL CABLES

There are two types of coaxial cable:


FINE CABLE (THINNET)

 THICKNET CABLE

THINNET CABLE: is a flexible coaxial cable about 0.64 cm thick. It can be used for most types of networks, it is a flexible cable and easy to handle. It can support a signal of an approximate distance of 185 m, before the signal begins to suffer attenuation. It is included in a group called THE RG-58 FAMILY and has an impedance of 50 ohm.

THICKNET CABLE: It is a 1.27 cm rigid coaxial, sometimes referred to as standard ETHERNET because it was the first type of cable with the Ethernet network. The greater the thickness of the copper core, the farther it can carry the signals. It can carry a signal of 500 meters. It is used as a central link or backbone to connect small networks based on thinnet.
A TRANSCEIVER designed for Ethernet, thicknet includes a connector known as VAMPIRO or FORADOR to establish the connection to the thicknet core.
THERE ARE TWO TYPES OF BRAIDED TORQUE CABLES

- UNPLASHED BRAIDED TORQUE CABLE (UTP)


SCREENED TWISTED TORQUE CABLE (STP)

 A series of twisted pair wires are often grouped together and enclosed in a protective sheath to form a cable. Braiding eliminates electrical noise from adjacent pairs and other sources such as motors, networks and transformers.



UNPLASHED BRAIDED TORQUE CABLE (UTP)With the 10baset specification, it is the best known type of twisted pair cable and has been the most used LAN wiring. The maximum cable length segment is 100 meters. It consists of 2 insulated copper wires the specifications dictate the number of interlocks allowed per cable foot; The number of interlocking depends on the purpose with which the cable is installed.

SCREENED TWISTED TORQUE CABLE (STP)Use a wrap with braided copper, more protective of higher quality than used in the utp cable. Stp also uses a foil surrounding each of the pairs of wires, offers excellent shielding in the stp to protect the transmitted data from external intermodulations, allowing it to withstand higher transmission rates than the utp at greater distances.



OPTICAL FIBER CABLE

This signals that are transported are digital data signals in the form of light modulated pulses. It is suitable for transmitting data at very high speeds and with large capacities. It consists of an externally thin glass cylinder, called a nucleus, covered by a concentric glass layer called a coating sometimes made of plastic.

Wireless transmission: they are radio waves are easy to generate, they can travel long distances and penetrate the building without problems, they are omnidirectional travel in all directions from the source, so the transmitter and receiver do not have to line up.
Microwave transmission: above 100 mhz the waves travel in a straight line can be focused on a narrow sickle. Concentrating all the energy in a small sickle with a satellite dish produces a much higher signal in relation to noise, but the transmitting and receiving antennas must align with each other.

Infrared waves: do not cross solids is an advantage so that an infrared system does not interfere with a similar system on an adjacent side. This system does not need a government license to operate in contrast to radio systems.
Transmission by light waves: it offers a very high bandwidth and a very low cost. Easy to install and does not require a license. The disadvantage is that laser beams do not penetrate rain and fog.

Wireless networks: they facilitate the operation where the computer cannot remain in one place, the current wireless networks offer speeds of 2mbps.

Types of Network Topology

TOPOLOGY: or logical form of a network is defined as the way to lay the cable to individual workstations; by walls, floors and ceilings of the building. There are a number of factors to consider to determine which topology is most appropriate for a given situation. The topology in a network is the configuration adopted by the workstations to connect to each other.

BUS TOPOLOGY

Network whose topology is characterized by having a single communications channel called a trunk bus or backbone connects to different devices or other nodes.


ADVANTAGE:

Ease of implementation
Growth and simplicity of architecture

DISADVANTAGES:

Limited channel lengths
A problem in the channel usually degrades the network

DOUBLE RING TOPOLOGY


It consists of two concentric rings where each network is connected even or more rings although the two rings are not connected to each other.

ADVANTAGE:

Architecture Simplicity
Ease of deployment and growth

DISADVANTAGES:

The channel usually degrades the network


TREE TOPOLOGY

 

It is a cable of ramifications and hierarchical information flow.

ADVANTAGE:

The wiring is point to point for individual segments
Support from a multitude of software and hardware vendors

DISADVANTAGES:

The size of each segment is determined by the type of cable if the segment falls apart.


RING TOPOLOGY

It consists of a single ring

ADVANTAGE:

Architecture Simplicity
Ease of implementation

DISADVANTAGES:

The channel usually degrades the network


STAR TOPOLOGY

 
It is the physical way in which all stations were connected to a single central node.

ADVANTAGE:

It allows the communication of the other nodes, presents means to prevent problems
Economic maintenance

DISADVANTAGES:

If the hub fails the network has no communication if the central node fails the entire network is disconnected


NETWORK TOPOLOGY

It is similar to the star topology, except that it has no central nodes.

ADVANTAGE:

Point to point wiring

DISADVANTAGES:

If the main segment fails, the entire network collapses


MESH TOPOLOGY

In which each node is connected to all nodes in this way it is possible to take messages from one node to another by different paths.

ADVANTAGE:

Offers superior redundancy and reliability
They are routable

DISADVANTAGES:

It is of low efficiency of connections and links due to the existence of redundant links

ELEMENTS OF A NETWORK

SERVER: it is the main processing element, it contains the network operating system and is responsible for managing all the processes within it, it also controls access to common resources such as printers and storage units.



WORKSTATIONS: sometimes called nodes, they can be personal computers or any terminal connected to the network. You work with your own programs or take advantage of existing applications on the server.

NETWORK OPERATING SYSTEM: it is the program that allows the control of the network and resides in the server.

COMMUNICATION PROTOCOLS: they are a set of rules that regulate the transmission and reception of data within a network.

NETWORK INTERFACE CARD: provides the connectivity of the terminal or user of the physical network, since it handles the communication protocols of each specific topology.

WIRING: is the cable that is going to be used in the network that is physical is called utp.

HUB OR CONCENTRATOR: in communications, distribution center, hub. A Hub is a network device that allows other computers or devices to connect to each other by retransmitting data packets from any of them to everyone. They have stopped being used because of the large number of collisions and network traffic they produce.

  SWITCH: it is a digital device of interconnection logic of computer networks that operates in layer 2 (data link level) of the osi model: its function is to interconnect 2 or more network segments, similar to bridges (bridges), passing data from one segment to another according to the Mac address of different frames in the network.

 The switches are used when you want to connect multiple networks, merging them into one. Like bridges, since they function as a filter in the network, they improve the performance and security of the lans.



REPEATER: it is an electronic device that receives a weak or low level signal and retransmits it to a higher power or level, so that longer distances can be covered without degradation or with tolerable degradation. The term repeater was created with telegraphy and referred to an electromechanical device used to regenerate telegraphic signals. The use of the term has continued in telephony and data transmission.

BRIDGE : it is a computer network interconnection device that operates in layer2 (data link level) of the osi model. It interconnects 2 network segments by passing data from one network to another, based on the physical destination address of each package. A bridge connects 2 network segments as a single network using the same network establishment protocol. It works through a table of Mac addresses detected in each segment to which it is connected. When it detects that a node of one of the segments is trying to transmit data to a node of the other, the bridge copies the frame for the other subnet. By using this machine learning mechanism, bridges do not need manual configuration.

The main difference between a bridge and a hub is that the second passes any frame with any destination for all other connected nodes, instead the first only passes frames belonging to each segment. This feature improves network performance by reducing useless traffic.

To make the bridging or interconnection of more than 2 networks, the switches are used.


ROUTER: It is a general purpose device designed to segment the network, with the idea of ​​limiting brodcast traffic and providing security, control and redundancy between individual brodcast domains, it can also provide firewall service and economic access to a WAN. It operates in layer 3 of the osi model and has more software facilities than a switch. When operating on a layer greater than that of the switch, the router distinguishes between different network protocols, such as ip, ipx, apple talk or decnet. This allows you to make a smarter decision than the switch, when forwarding packets.



GATEWAY: A device that is frequently a computer, which allows networks to be interconnected with protocols and different architectures at all levels of communication. Its purpose is to translate the protocol information used in a network to the protocol used in the destination network.

The IP address of a Gateway (or gateway) often resembles 191.167.1.1 or 191.166.0.1 and uses some predefined ranges, 127 xxx, 10 xxx, 172 xxx, 192 xxx, which encompass or reserve networks local, also it should be noted that necessarily a team that fulfills the role of gateway in a network, must have 2 network cards.

 MODEM: It is a device used to modulate and demodulate a signal called carrier by another input signal called modulator. The modulating signal constitutes the information that is prepared for a transmission (a modem prepares the information to be transmitted, but does not perform the transmission). The modulator modifies some characteristic of the potador so that a signal is obtained, which includes the information of the modulator. Thus the demodulator can recover the modulating signal can recover the original modulating signal, removing the carrier. The characteristics that can be modified from the carrier signal are:

• Amplitude, resulting in an amplitude modulation (am / ask).

• Frequency, resulting in a frequency modulation (fm / fsk).

• Phase, resulting in a phase modulation (pm / psk).