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Network Throughput

Throughput can be defined as the amount of material transferred through an system or process, if associated with the Network, the material referred to here is "Packet", while the system through which the packet is passed can be a "link" which is Physical or Virtual.

When discussing Network Throughput, measurements are usually carried out per units of time, between two devices, and represented in Bits per second (Bps), Kilobits per second (Kbps), Megabits per second (Mbps), Gigabits per second (Gbps), and so on.

Network throughput can be defined as the amount of data transferred through a medium or connection. There is such a thing as constant throughput means the rate at which data is received at one end-system (in bits / sec) at a time.

Bandwidth VS Throughput

What is the difference between Bandwidth and Throughput? Bandwidth is defined as the maximum transfer capacity from a network. Bandwidth doesn't measure the transfer speed of the network, but it does lots of data that can be transferred at the same time. If network A has bandwidth is 5 times higher than network B, and network B can send messages 1MB in 1 second, then network A can send 5MB messages within 1 second too. The increase in bandwidth doesn't increase the speed, however it does increase throughput.

try to look at the illustration below.

pipe-image

Of the two pipes in the image above, by default Pipe B must drain more water because Pipe B is thicker and has a larger diameter. However, actually it all depends, depending on what? depending on many factors.

If water flows with maximum capacity through both pipes, then Pipe B will drain more water. But what if more water enters through pipe A than pipe B? or what if there is dirt or debris in Pipe B which blocks the flow of water in Pipe B so that more water flows from Pipe A?

In short, we can conclude that under ideal conditions and at capacity maximum, Pipe B delivers more water than Pipe A. However, there could be several factors that can cause Pipe A to flow more water than Pipe B in time units.

Using the analogy above, we can liken the bandwidth as the thickness of the pipe (capacity pipe maximum in theory). Meanwhile, throughput can be likened to the amount actual flow of water per unit time. Therefore, despite the bandwidth set a throughput limit, throughput can be influenced by other factors.

Factors That Affect The Throughput Of A Network

  1. The Limitation Of Transmission Medium
    The transmission medium does have a limit or we can say as a theoretical rate of the medium that can only reach to maximum capacity of it self and limit the throughput too. So when you can only have a theoretical rate capacity of the medium is around 100 Mbps that does mean the throughput only can reach a maximum of 100 Mbps data rate capacity and sometimes its practical rate capacity is only using 95% percent of its theoretical rate capacity.

  2. Enforced Limitation
    Let's say if we were going to transfer some link capacity from some place to another place, it must be the transfered link capacity will have a bigger and larger link medium to be transfered from one place to another because it is naturally based on the current technology. It will immediately find a medium that can transfer more than just the link capacity can cover the medium. But it will affect the throughput because the deliverer of the link capacity will try to enforce the link capacity to fit to the transfer medium or the capacity of the medium and will affect the actual throughput.

  3. Congested Network
    When we have some data with a lot of rate capacity and cannot make up the medium transfer rate capacity, it will make the data congested in the line and make the throughput less available on the network. The more congested of the network is the less throughput that the network get.

  4. Latency
    The packet from the sender to the deliverer can get a little bit slower than before. It's because of the delay from the packet itself. They can make it alot slower than before because of the latency or delay on the time of the packet delivery. It will affect the throughput too, because if we get a latency to the network packet it will slowdown anothet packet to move from one place to another, hence it will make the throughput much lower than before.

  5. Packet Loss and Errors
    With the same ability as a latency would do to the packet. It will make the throughput got much lower than before because of the time to retransmitted the missing packet to the destinations. The different schedule of the transmission can cause the lower throughput and affect the troughput. Some of the cause of latency and packet loss is usually because of damaged devices, bottlenecks, and security attacks.

  6. Some Protocol Operations
    It can also affect the throughput because of protocol operations to ensure the transmission go smoothly. Sometimes the protocol operations active to make flow control and avoid congestions on the network. They will have a feature to make the packet prefectly transmitted to the destinations, but it also will affect the how much the packet got transmitted and when the packet got transmitted. That's why protocol operations could affect the throughput of the transmission of a network.

Optimization Throughput

The throughput on a network can be improved once the cause of low/reduced throughput has been identified as listed under the “Factors that affect Throughput” section above:

  • Bandwidth can be increased to provide more throughput especially in cases where the network is overloaded i.e. the bandwidth cannot support the load on the network.

  • Bottlenecks should be identified and removed from the network. This will go a long way in reducing latency and packet loss/errors, and thereby reducing congestion on the network. Note that bottlenecks can be as a result of medium limitation e.g. using 100 Mbps interfaces instead of 10 Gbps interfaces.

  • Faulty devices/components should be replaced and overburdened devices should be upgraded.

  • Quality of Service (QoS) can be applied to ensure that critical traffic is unaffected by network congestion. While this will not improve overall throughput on the network, it will ensure good throughput for critical traffic.

References

James Kurose and Keith Ross, Computer Networking: A Top-down Approach 7th Ed., Pearson, 2017.

https://www.pcwdld.com/network-throughput

https://www.youtube.com/watch?v=qL7ZGeSoQRM