A hub or hub is a device that enables centralized wiring a network and to enlarge . This means that the device receives a signal and repeats the signal emitted by the different ports.
hub (hub) is the most basic connection device. It is used in local networks with a very limited number of machines. There is only one power strip that amplifies the signal RJ45 network (base 10/100). In this case, a request aimed at a particular PC on the network will be sent to all PCs on the network. This greatly reduces the bandwidth and causes problems of listening on the network. Network hub is a device in which we find many network ports, I think the smallest I've seen is 4 network ports. It takes a computer signal and redistributes all network ports that are under the next signal. There are many types depending on the technologies with which to design and shape but usually are classified as passive, active and intelligent. Liabilities that do not need power, take the signal and redistributes it simply and are recommended for cases that are networked computers that are relatively close. The active power is required, ie extra power needed, "up" signal received, ie make it a little harder, then distributed and are recommended when computers are not close.
The intelligent hub or hub has a processor that helps distribute the signal more quickly, it looks like a router or router but the signal is distributed equally on all ports so there is no router. The needs of people send in the use of them if you have a small network and located in a room should ideally be a passive hub, if the network is large and covers several rooms it is recommended as an intelligent hub. The Hub also respond to the needs of network configuration. For example they are ideal for star-shaped networks, ie where there is a distribution point (hence the name) where several computers communicate with a server or a router.
As for the usb hub which today are popular because they allow to connect multiple printers, scanners and up to several computers (usb networks are in their infancy but are extremely easy to set up), in theory to a USB port may branch up to 32 ports through a hub or more on but much weaker signal ends. What is often recommended in these cases is that ACADA USB port of the computer case at most, are placed eight ports, with the best four.
The intelligent hub or hub has a processor that helps distribute the signal more quickly, it looks like a router or router but the signal is distributed equally on all ports so there is no router. The needs of people send in the use of them if you have a small network and located in a room should ideally be a passive hub, if the network is large and covers several rooms it is recommended as an intelligent hub. The Hub also respond to the needs of network configuration. For example they are ideal for star-shaped networks, ie where there is a distribution point (hence the name) where several computers communicate with a server or a router.
As for the usb hub which today are popular because they allow to connect multiple printers, scanners and up to several computers (usb networks are in their infancy but are extremely easy to set up), in theory to a USB port may branch up to 32 ports through a hub or more on but much weaker signal ends. What is often recommended in these cases is that ACADA USB port of the computer case at most, are placed eight ports, with the best four.
A hub works by repeating each data packet in each one of the ports which account, except that it has received the package, so that all points have access to data. Also responsible for sending a signal shock to all ports if it detects a collision . They are the basis for networks of topology type star. Alternatively there are systems in which computers are connected in series, ie a line connecting some or all computers to one another, before reaching the central computer. also called multiport repeater, there 3 classes. Liabilities: You do not need electricity. It is dedicated to networking.
Active: Needs food. In addition to concentrating the wiring, regenerates the signal, remove noise and amplify the signal
Smart: Also called smart hubs are active hubs including microprocessor.
Within the OSI model the hub operates at the physical layer , like repeaters, and can be implemented using only analog technology. Simply joins connections and does not alter the frames that arrive.
Considering the above we can draw the following conclusions:
The hub sends information to computers that are not interested. At this level there is only one recipient of the information, but to ensure that you receive the hub sends the information to all computers connected to it, and sure hits.
This generates added traffic collision more likely. A collision occurs when a computer wants to send information and issued simultaneously with another computer that does the same. By colliding the two messages are lost and need to relay. Moreover, as we add computers to the network will also increase the likelihood of collision. A hub works
at the speed of the slowest device on the network. If we observe how the hub is not capable of storing anything. So if a computer that emits at 100 Mb / s you convey to a 10-Mb / s something is lost in the message. In the case of ADSL the routers typically operate at 10 Mb / s, if we connect to our home network, the entire network will operate at 10 Mb / s, but our cards are 10 / 100 Mb / s.
A hub is a simple device, this affects both traits. The price is cheap. Add delays resulting from the transmission package to all computers on the network (including those who are not recipients of it).
Hubs were popular until the cheaper switch having a similar function but provide more security against programs like sniffer. The availability of ethernet switches low price has made them obsolete, but can still be found in older plants and in specialized applications.
Hubs also often come with a BNC and / or AUI connector to allow connection to 10Base5, 10Base2 or network segments. USES
Historically, the main reason for purchasing hubs rather than switches was the price. This has been largely eliminated by reductions in the price of switches, but hubs can still be useful in special circumstances:
A protocol analyzer connected to a switch not always receive all packets from that switch separates the ports into different segments. The protocol analyzer connected to a hub can see all traffic on the segment. (The expensive switches can be configured to allow a port to listen for traffic from another port. This is called port mirroring. However, these costs are much higher).
Some groups of computers or cluster require each team member to receive all traffic is going to the pool. A hub will do this, of course, use a switch in these cases requires the application of special tricks.
When a switch is accessible for end users to make connections, for example, in a conference room, an inexperienced user can reduce the network by connecting two ports together, causing a loop. This can be avoided by using a hub, where a loop is broken in the hub to other users. (It can also be prevented by purchasing switches that can detect and deal with loops, for example through the use of Spanning Tree Protocol.)
A cheap hub with a 10BASE2 port is probably the easiest and cheapest way to connect devices that only support 10BASE2 to a modern (not usually come with 10BASE2 ports switches flights
A protocol analyzer connected to a switch not always receive all packets from that switch separates the ports into different segments. The protocol analyzer connected to a hub can see all traffic on the segment. (The expensive switches can be configured to allow a port to listen for traffic from another port. This is called port mirroring. However, these costs are much higher).
Some groups of computers or cluster require each team member to receive all traffic is going to the pool. A hub will do this, of course, use a switch in these cases requires the application of special tricks.
When a switch is accessible for end users to make connections, for example, in a conference room, an inexperienced user can reduce the network by connecting two ports together, causing a loop. This can be avoided by using a hub, where a loop is broken in the hub to other users. (It can also be prevented by purchasing switches that can detect and deal with loops, for example through the use of Spanning Tree Protocol.)
A cheap hub with a 10BASE2 port is probably the easiest and cheapest way to connect devices that only support 10BASE2 to a modern (not usually come with 10BASE2 ports switches flights
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