Network Hub

A network hub allows the interlinking of several PCs and devices together to form a network. It can be considered as a normal junction box that passes along a signal to all devices connected to it.

Most technically minded people associate hubs with a primitive form of networking with the notion of a packet collision occurring. Packet collisions give network hubs a tarnished name, so what exactly is a packet collision? Well, if we take the most basic of examples:

We have a 1 network hub with 2 ports and 2 PCs, both of which are connected up to the hub. When one PC wishes to share a slice of information with another, it sends the packet of information through an ethernet cable (standard network cable) to the hub which then shares the information with the other PC. However if the other PC also decides to share a packet of information at the same time, a packet collision occurs and will need to be routinely resolved by both PCs.

Each ethernet adapter has a receiving end and a transmitting end. The receiving end of the cable has to listen out for packets of information and thus the transmitting end can only work at half the flow. Therefore, it is impossible for an ethernet adapter to be able to send and receive information at the same time, prohibiting a free flow of information. Without going into specifics about bandwidth sharing, this limitation basically means that all PCs connected to a hub have to share a certain amount of bandwidth.

So if one PC is downloading a large file from another PC, the network then becomes congested and any other computers will experience a very slow file transfer rate during this time.

A network hub is never aware of the intended destination of any data it receives; it simply acts a broadcasting device allowing any devices connected to it, the right to take packets of data from it.

3 types of hub exist:

  • Passive: A small hub that is actually part of an ethernet cable and requires no outside power source, as it does not renew any of the data signals.
  • Active: The opposite to a passive hub, the active hub does renew the data signal and therefore requires an outside power source to function.
  • Intelligent: Like an active hub, it renews and amplifies a data signal but it also provides an error detection function for excessive packet collisions.

Crossover cables are a far better option if you simply want to share information between 2 devices. Data collision using this method is non-existent, as a process called ‘auto negotiation’ takes center stage allowing the ethernet adapter to operate in full flow (full duplex). The crossover cable hardwires the transmitter of one end of the cable to the receiver on the other end of the cable and thus data can be sent concurrently with a top end bandwidth of 200Mbps shared at a rate of 100Mbps each way.

Network hubs are not used as often as they used to as they have largely been replaced by the newer technology of network switches. Network switches are apble to determine the source and destination of the packets they receive and send them where they need to go. This new technology eliminates the packet collision problem as well as conserves network bandwidth.

Many still had network hubs rather than switches, even after the technology was introduced, because switches used to be quite a bit more expensive than network hubs. As time went on, the costs of network switches has come down to a comparable level so network hubs are now only used in certain circumstances which the average user will probably never encounter.

This Network Hub Review is Written/Updated on Sep 23rd, 2009 and filed under Computer Hardware. Both comments and pings are currently closed.

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