How is Network Performance Measured?

TYPES OF NETWORK LINKS

Network connection speed and direction is determined by the physical link between a computer and another network device as well as the supporting software. The following connection types are commonly used. Note, however, that some of these are considered obsolete.

10-Base 2: This link is designed for use in a bus topology. Each machine is connected to two others, with the exception of the machines at the end of the bus. If one machine develops a fault it can severely impact or disable the network as a whole. This variety of link is easily identified by its use of coaxial cable.

10-Base T Half-Duplex: This link type allows for the transfer, optimally, of 10 megabits of data per second. This equates to roughly 1,250 kilobytes per second. These links can operate at half-duplex or full-duplex. The former is mainly used for troubleshooting or if full-duplex does not work. It only permits data to be sent or received, but not both at the same time. Full-duplex permits full bidirectional communication.

100-Base T Half-Duplex: This is the most common network link in use today. It supports 100 megabits of bandwidth, which equates to roughly 12.8 megabytes per second. The half-duplex version of this link can send or receive but not perform both tasks at the same time. The full-duplex version is fully bidirectional. This link is fast enough for even intensive network applications. A faster link is typically only needed for extreme situations such as streaming media or web server connections.

Gigabit Ethernet: This link supports up to 1 gigabit of total bandwidth. This equals approximately 128 megabytes per second. This type of link is sufficient even for extremely busy networks and very high speed DOCSIS 3.0 and fiber Internet connections. This link is being widely adopted as the standard and is gradually replacing 100-Base T.
Gigabit Ethernet requires Category 6 Ethernet cable for proper signal delivery.

10 Gigabit Ethernet: Similar to Gigabit Ethernet, this link supports a theoretical 10 gigabits of bandwidth, which equates to 1.28 gigabytes per second. Few applications reasonably require this sort of bandwidth.

MEASURING BANDWIDTH

Data is sent along a network link in the form of “bits,” or individual on and off signals. It is sent serially, which means one bit at a time. Network connections are typically rated in “megabits”, which refers to approximately one million bits. A gigabit refers to one billion bits. Although this is the common nomenclature to describe network data speeds, most users are more perceptive of the rate at which files are transferred over the network. This is measured in bytes, not bits. To convert a value from bits to bytes, divide by eight. For example, a 1 megabit connection is approximately 1,000,000 bits per second but only 125,000 bytes per second.

MEASURING LATENCY

While bandwidth measures how quickly data can be transferred once it begins to flow, latency is an indicator of how long communication across network links takes. It is typically tested using a “ping” command. This command sends a small packet of data to its destination, where it then returns to the source. The round-trip time is measured in milliseconds. In the case of latency, lower is better. Good “ping times” are below 100ms.

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