What is the hub for?A hub is a network device that connects various network nodes,for example,in Ethernet,connected in a star configuration.In the OSI(Open Systems Interconnection)reference model,a hub is classified as a class 1 device operating at the physical layer.Their main task is to interconnect several computers and immediately forward received data.Hubs are usually made of plastic,run on external electricity,and contain anywhere from 4 to 16 ports,or physical connections.Their maximum bandwidth is usually 10/100 Mbit per second.

　　How do they work?

　　The hub receives the data and sends it in its entirety to all connected devices(hosts).All ports of a hub operate at the same speed and are in a collision domain.Unlike other network devices,hubs don't offer the option to control or exclude only individual receivers.This means that during transmission,all packets are always forwarded to all computers.This means that even devices that the data was not intended for will receive the data.Since all hosts are occupied in this way,other devices cannot send any data themselves during this time.Instead,concurrent requests will be processed one after the other.

　　If more hosts are needed,one center can be connected to another.This connection is created with a simple crossover cable through one of the ports.However,the number of hosts is automatically limited by the 5-4-3 rule or the repeater rule.This means that up to five segments with four repeaters can be used between two end devices.Also,when using a hub,the connected hosts share the entire bandwidth.This inevitably results in a loss of speed,especially when transferring large packets.

　　Disadvantages of hub networks

　　Hubs are an obsolete technology.In addition to the speed loss mentioned above,and the lack of flexibility in terms of data transfer and selected recipients,hub systems are also relatively vulnerable to security issues.For example,systems cannot be isolated and data communication does not occur in a protected manner.Any security or privacy concerns immediately affect all connected hosts.