Definition:

In computer networking, Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second. Fast Ethernet increased speed from 10 to 100 megabits per second (Mbit/s). Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE 802.3z, and required optical fiber.

What is the transfer speed of Gigabit Ethernet?

How fast is a gigabit? If you hear the prefix "giga" and assume 1,000 megabytes, you might also figure that a gigabit network should deliver 1,000 megabytes per second. If this sounds like a reasonable assumption to you, you’re not alone. But unfortunately, you’re going to be fairly disappointed.

So what is a gigabit? It is 1,000 megabits, not 1,000 megabytes. There are eight bits in a single byte, so let’s do the math: 1,000,000,000 bits divided by 8 bits = 125,000,000 bytes. There are about a million bytes in a megabyte, therefore a gigabit network should be capable of delivering a theoretical maximum transfer of about 125 MB/s.

While 125 MB/s might not sound as impressive as the word gigabit, think about it: a network running at this speed should be able to theoretically transfer a gigabyte of data in a mere eight seconds. A 10 GB archive could be transferred in only a minute and 20 seconds. This speed is incredible, and if you need a reference point, just recalls how long it took the last time you moved a gigabyte of data back before USB keys were as fast as they are today.

Armed with this expectation, I’ll move a file over my gigabit network and check the speed to see how close it comes to 125 MB/s. We’re not using a network of wonder machines here, but we have a real-world home network with some older but decent technology.

Copying a 4.3 GB file from one of these PCs to another five different times resulted in a 35.8 MB/s average. This is only about 30% as fast as a gigabit network’s theoretical ceiling of 125 MB/s. 

Conclusion:

Gigabit Ethernet, a transmission technology based on the Ethernet frame format and protocol used in local area networks (LANs), provides a data rate of 1 billion bits per second (one gigabit). Gigabit Ethernet is defined in the IEEE 802.3 standard and is currently being used as the backbone in many enterprise networks. Gigabit Ethernet is carried primarily on optical fiber (with very short distances possible on copper media). Existing Ethernet LANs with 10 and 100 Mbps cards can feed into a Gigabit Ethernet backbone. An alternative technology that competes with Gigabit Ethernet is ATM. A newer standard, 10-Gigabit Ethernet, is also becoming available.