What you should know about Gigabit Ethernet

Gigabit Ethernet is part of the Ethernet family of computer networking and communication standards. The Gigabit Ethernet standard supports a theoretical maximum data rate of 1gigabit per second (Gbps) (1000 Mbps).

What Kind of Cables are Required to Support Gigabit Ethernet?
When first developed, some thought achieving gigabit speeds with Ethernet would require using fiber optic or other special network cable technology. The 1000BASE-X cabling standards support Ethernet over fiber.
However, today's Gigabit Ethernet works well using twisted pair copper cable (specifically, the CAT5e and CAT6 cabling standards) similar to older 100 Mbps Fast Ethernet (that works over CAT5 cables). These cable types follow the 1000BASE-T cabling standard.

How Fast is Gigabit Ethernet in Practice?
Because of factors like network protocol overhead and re-transmissions due to collisions or other transient failures, devices cannot actually transfer useful message data at the full 1 Gbps (equal to 125 megabytes per second) rate.
 
Under normal conditions the effective data transfer over the cable may still reach 900 Mbps at least for brief periods.
On PCs, disk drives can greatly limited the performance of a Gigabit Ethernet connection. Traditional hard drives spin at rates between 5400 and 9600 revolutions per second, that can only handle between 25 and 100 megabytes per second of data transfer.
Finally, some home routers with Gigabit Ethernet ports may have CPUs that are unable to handle the load needed to support incoming or outgoing data processing at the full rates of the network connection. The more client devices and concurrent sources of network traffic, the less likely for a router processor to be able to support maximum speed transfers over any one link.

Does a Device Support Gigabit Ethernet?
A person usually cannot tell simply by looking at the physical device whether it supports Gigabit Ethernet. Network devices provide the same RJ-45 connection type whether their Ethernet ports support 10/100 (Fast) or 10/100/1000 (Gigabit) connections.
Network cables are often stamped with information about the standards they support. These markings help confirm whether a cable is capable of operating at Gigabit Ethernet speeds but do not indicate whether the network is actually configured to run at that rate.
To check the speed rating of an active Ethernet network connection, find and open up the connection settings on the client device. In Microsoft Windows, for example, the Network and Sharing Center allows clicking on a link which displays information about an active connection.

What Happens if A Device Only Supports 100 Mbps Ethernet?
All newer broadband routers now support Gigabit Ethernet along with other mainstream computer network equipment. Gigabit Ethernet also provides backward compatibility to older 100 Mbps and 10 Mbps legacy Ethernet devices: Connections to these devices function normally but perform at the lower rated speed.