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Monday, February 11, 2013

How fast is a Gigabit Network? (Transfer Rate)

When talking about a Gigabit Network, the first thing we have to address is Bits versus Bytes.


When we talk about network hardware, we are commonly using the term Megabit.  For example, a 10/100 Fast Ethernet Network Card is 10/100 Megabit.  1 Gigabit (Gb) equals 1024 Megabits (Mb). 


When Microsoft Windows displays the network transfer speed, it is displayed using Megabytes (mb) not Megabits (Mb). One Megabit (Mb) equals 0.125 Megabytes (mb).  There are 8 Megabytes (mb) in 1 Megabit (Mb).

Theoretical Transfer Speed

Since there are 8 Megabytes (mb) in 1 Megabit (Mb), we can determine the theoretical maximum network transfer speed in Megabytes.  1 Gigabit equals 1024 Megabits which equals 128 Megabytes.  In theory, a 1 Gigabit Network should provide us with a transfer speed of 128 Megabytes.

Average Transfer Speed

On a 100 Megabit network using CAT-5/CAT-6, the average transfer rate is 8.6 Megabytes to 12.5 Megabytes.

On a Gigabit network (1024 Megabit) using CAT-5/CAT-6, the average transfer rate is 21.5 to 45 Megabytes.

The Question

On a Gigabit network using CAT-5/CAT-6, why isn't the average transfer rate closer to the theoretical maximum of 128 Megabytes? 

The Simple Answer

The simple answer is the transfer rate is typically limited by the maximum transfer rate of the computer hard drive found in the origin and/or destination computer.  Ideally, both the origin and destination are using a Modern Computer with a RAID Controller, SSD Drives, Optimal Motherboard Bus Architecture, Multi-Core Processor, Recommended RAM and Recommended Swap File with plenty of Free Space.  Using this configuration, you should be able to obtain an average transfer rate of 72 Megabytes and greater.

The Complete Answer

On a computer network (WAN, LAN, VPN, etc.), the data transfer rate for Client/Server can be impacted by:
  • RAID Controller
  • Hard Drive Type
  • Motherboard Bus Speed
  • Processor
  • RAM
  • Swap File Setting
  • Free Disk Space
  • Free RAM
  • Flow Control
  • Auto Negotiation
  • Shared Resources
  • Cabling Quality and Type (Fiber, CAT-5 and CAT-6)
  • Cabling Length
  • Network Card Driver Version
  • Network Card Firmware
  • Electrical Interference
  • Protocol Type and Overhead
  • Hops (Routers, Switches, Hubs, Firewalls)
  • Poorly Designed or Multiple Antivirus
  • Trojan
  • Open Relay
  • Spam 
  • ISP Circuit Committed Information Rate
  • ISP Type and Bandwidth

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