How is the Bandwidth of a Network Measured?

[nelson]

Bandwidth can also be Evaluated Concerning a Network

Bandwidth also sometimes refers to the theoretical maximum transmission rate of a communications channel. Normally, people think of bandwidth as the "speed" of a networking link; actually, bandwidth indicates how much data can be transferred over the line during a certain time period, while speed indicates the rate at which data is transferred at any instant.

Assessment of bandwidth is crucial in understanding network performance and its sufficiency for user needs and application requirements. In this elaborative discussion, we're going to review a number of techniques used in measuring bandwidth, units of measurement involved, and what aspects affect the length.

 

Understanding Bandwidth

Before looking at the measurement of bandwidth, it is necessary to take a moment to clearly define what is meant by the term bandwidth.

Bandwidth describes the maximum amount of data that can be transmitted in any given time, measured in bps, which denotes bits per second. High bandwidth allows more data to travel over a network at any given time.

Bandwidth can be envisaged as the flow of water through a pipe. The volume of water able to flow at any one time will be decided by the width or diameter of the pipe. The greater the diameter, or more simply the greater the bandwidth, the more volume of water or data that can flow through the pipe during a given period.

 

Measurements of Bandwidth

Units of measurement for bandwidth are usually measured in terms of bits per second. The prefixes change depending on the scale of the measurement. Some include the following: 

bps: This is the basic unit used in measuring bandwidth.

1,000 bits per second = Kbps
1,000,000 bits per second = Mbps

1,000,000,000 bits per second = Gbps

1,000,000,000,000 bits per second = Tbps.

Note that these are usually applied to refer to network throughput—the rate at which data is transferred, not the amount of data stored or the size of the data itself.

 

How Bandwidth is Measured

There are numerous techniques and tools for network bandwidth measurement. Methods applied are based on whether the measurement is made from a network level, link level, or user experience perspective.

a) Throughput Measurement

Throughput generally means the actual measure of bandwidth usage on any given network. Bandwidth is the theoretical maximum rate of transfer, but the throughput is the actual rate of transfer. Actual rates are normally lower than the theoretical maximum due to network congestion, latency, and packet loss.

Throughput Measurement Tools

Speed Test Sites: These are websites like Speedtest.net, Fast.com, among others. These sites measure the download and upload speeds of one's internet connection. Most of them do their tests based on the speed at which data is transferred between the client-your device-and a server.

iPerf: A command-line tool that is usually used to measure bandwidth between two points in a network. The operation of sending packets of data via a TCP or UDP connection and afterwards determining the speed at which data took to get to the other end can provide an accurate bandwidth measurement.

Wireshark: Although it is normally used as a network protocol analyzer, it can perform some capturing over networks and give details regarding the data transferred. It can provide an estimated throughput.

b) Network Simulation for Bandwidth Measurement

Network simulators can reveal the actual condition of the traffic by simulating the pattern of the traffic and calculating the expected bandwidth under different conditions. These may be based on real events that happen around the world, such as latency, packet loss, and jitter.

Examples of Tools

ns-3: This is one of the renowned free and open-source network simulators, capable of modeling and investigating bandwidth in various network topologies under different traffic conditions.

GNS3: It is a network emulator for emulating complex network topologies and measure bandwidth between nodes.

c) Link Capacity Tests

In general, link capacity refers to the maximum theoretically available bandwidth for a physical medium or link, which can be anything from fiber optic, Ethernet, or even wireless. Normally measured by sending traffic over the link and by determining at what point the link starts to degrade due to congestion.

Testing Approaches

Ping Test: Although it does not directly measure bandwidth, a ping test does convey information about the latency times and how many packets can be thrown across a link before congestion starts to kick in.

Path MTU Discovery: The bandwidth usage depends on it since it determines the largest MTU size that could be sent without fragmentation.

d) Quality of Service (QoS) Tools

Generally, QoS tools are deployed by utilizing the control and monitoring over the bandwidth consumption of a network administrator while offering quality service for mission-critical applications. QoS tools may analyze available bandwidth, prioritize traffic, and optimize performance in a network.

QoS Tools Examples

SolarWinds Bandwidth Analyzer Pack: A complete set of utilities and tools for real-time monitoring of network bandwidth, analysis of throughput, and detection of problems.

PRTG Network Monitor: This is used in bandwidth usage monitoring to find out network bottlenecks and measure available bandwidth. Bandwidth Measurement When a bandwidth measurement is done, the resulting value can be affected by many factors. Some of the common ones are:

 

Factors Influencing Bandwidth Measurement

a) Network Overload
High network traffic can be represented as overloaded, which in turn limits available bandwidth. With more users or devices on a network, actual throughput compared to the theoretical value can be much lower.

b) Packet Loss

The effective bandwidth decreases if the packets get lost during transmission because the lost packets have to be retransmitted. Along with a minimum speed requirement, there is low latency for some applications, including video streaming or VoIP. This again is a significant concern for them.

c) Delay

Time in milliseconds, which the data packets take to travel from sender to receiver reduces the effective bandwidth for the latency-sensitive protocols like TCP.

d) Jitter

Jitter is the variability in the time of arrival for packets. Applications requiring steady timing, such as video calling and online gaming, are severely affected by high levels of jitter. It can even give the illusion of lower effective bandwidth.

e) Protocol Overhead

The actual bandwidth utilized for transmitting data is inferred by the reduction of total bandwidth by protocol overhead. Examples of protocols with different magnitudes of protocol overhead include TCP and UDP. Protocol overhead includes header data carried by each packet, error correction, and packet retransmission.

f) Hardware Limitations

Devices used in the past for transmission and reception of data include routers, switches, and network cards each have limits of bandwidth. Bottlenecks, or limitations, in older or lower capacity hardware reduces the full possible bandwidth that can be achieved by a network.

g) Transmission Medium

Another factor affecting bandwidth is the physical medium over which the data are sent. Fiber optic cables, for example, have far greater bandwidth than copper cables, such as DSL or coaxial and those cables in turn provide far greater bandwidth compared with wireless systems.

 

Interpretation of Bandwidth Measurements

Once bandwidth has been measured, it must be interpreted in context with the requirements of the network:

Expected Bandwidth versus Utilized Bandwidth: If the actual bandwidth utilization is considerably lower than the expected amount, it might be due to network congestion, faulty hardware, or interference.

Bandwidth Utilization: Sometimes bandwidth is available but is not utilized. This may be because of inefficient applications that are not configured properly or a resource contention issue.

Different Networks, Different Bandwidth: The bandwidth comparison for different kinds of fiber optic, DSL, and 5G should be given in order to incorporate the fact that this maximum capability is just one of the many defining parameters of the bandwidth of a network, with their performance and suitability falling into very distinct categories.

 

Summary

There are various techniques, measuring tools, and considerations applied in the measurement of network bandwidth. From throughput tests using iPerf to real-time bandwidth monitoring using tools such as SolarWinds and PRTG, network administrators and network engineers depend on these metrics to know a network is capable of sustaining any given demands on it. Bandwidth is not intrinsically a fixed quantity; it changes around due to congestion, packet loss, latency, and jitter. The ability to make this differentiation is critical in measuring and interpreting bandwidth for effectiveness.
 

Edited November 8 by nelson