What is Hub ?
What is Hub or Concentrator :
A hub is a device used to connect all of the computers on a star or ring network. Hub or concentrator works at Passive Hubysical layer of OSI reference model.
A hub is a multi port repeater. Hubs have anywhere from and to over 400 Ports. When a signal is received on one port of the hub it is regenerated out all the other ports.
Installing hub is very simple, just connecting it to power source and plugging in cables connected to the network interface adapter in your computers.
All network (except those using coaxial cable) require a central location to bring media segment together. These central locations are called hubs or concentrators.
Hubs are special purpose repeaters that overcome the electromechanical limitations of a media signa; path.
The hub organizes the cables and transmits incoming signals to other media segments.
Two important properties of Hub :
1) Hubs echo all data from each port to all other ports on the hub. Because of this echoing, no filtering or logic occurs to prevent collision between packets being transmitted by any of the connected nodes.
2) Hubs posses automatic partitionning capability. Where the hub can automatically partition any node having trouble from the other nodes, if the hub port is receiving excessive packets that are flooding the network or if any serious problem detected for a ginev port on the hub.
Advanced built-in features of the Hubs :
1) Built-in management :The hub can be centrally managed over the network using SNMP(Simple Network Management Protocol) or other network management protocols and softwares.
2) Auto-sensing of different connection speeds :A hub that can automatically detect and run each node at either 10 Mbps(10 Base T) or 100 Mbps(100 Base T) are common.
3)High speed uplink that connects the hub to a backbone :A 10 Mbps hub usually operates at 10 times the basic speed that is uplink ports run 1 Gbps.
4) Built-in bridginig and routing fuunctions :That is not require seperate device to perform bridging and routing.
5) Built in switching :Nodes on hubs can be switced insteed of shared.
Following are three types of Hubs :
1> Passive Hubs
2> Active Hubs
3> Intelligent Hubs
1> Passive Hub :Unlike standalone repeaters. hub supplies cable connection by passing all the signals entering the device throough any port out through all other ports. Passive hub operates only at the Passive Hubysical layer, has no intelligence and does not amplify or modify the signal in any way. Maximum distanch covered by Passive Hub hub is about 300 feet. Passive Hub do not require electrical power to run.
2> Active Hub :Active Hub is that regenerates or amplifies the signals. Because of this, the diatance between devices can be increased. Some Active Hubs amplify noise in the signal. Active Hubs are expensive than Passive Hub. Active Hub functions as repeaters, they are some times called as multiport repeaters. Maximum distanch covered by Active Hub hub is about 2000 feet. Active Hub requires electrical power to run.
3> Intelligent Hub :Intelligent Hubs are units that have integrated management capability. Intelligent hub regenerates the signal and performs some network management and intelligent path selection. Intelligent Hub monitor rhe operation of each port.The network management capability is to provide the network administrator to remotely control the connection to be isolate particular segmants. Intelligent Hubs have ability to offer flexible transmission rates to various devices. This supportes standerd transmission rates of 10, 16 & 100 Mbps to desktop system using standard topologies such as Ethernate, Token Ring or FDDI.
Advantages of Hubs :
1> No need of configuration.
2> Active Hubs can extend maximum network media distance.
3> No processing is done at the hub to slow down performance.
Disadvantages of Hubs :
1> Passive Hub can greatly limit maximum media distance.
2> Hub have no intelligence to filter traffic, so all data is sent out to all ports whether it is needed or not.
3> Hubs can act as repeaters, networks using them must follow the same rules as repeaters.
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