I have the following Questions regarding Delays and throughput

  1. Is transmission rate same as Bandwidth?
  2. What is throughput and while calculating throughput why do we consider transmission delay. Shouldn't we also consider the propagation delay?

I know the question might sound silly,but please help.

  • 1
    bandwidth = maximal transmission rate, as is discussed all over internet. – Valentin Tihomirov Mar 23 '16 at 12:14
  • Delay could play a part in throughput only with certain protocols. For Instance, it will affect TCP, but UDP, as an uninterrupted sender, will not be affected by delay. – Ron Maupin Mar 23 '16 at 13:55
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 13 '17 at 20:00

Is transmission rate same as Bandwidth?

In essence yes, with some small adjustments for the difference between the clocking of the media ("bandwidth") and the actual rate at which packets are accepted onto the media (ie, minus minor overheads like ethernet headers, SDH segmentation, forward-error control, tunnelling like VLANs, MPLS, GRE).

We can do "traffic shaping" in the router so that the packet transmission rate presented to the media is substantially less than the available transmission rate of the media. This is how you can order a 200Mbps service over a gigabit ethernet fibre.

What is throughput

Throughput is the speed visible to the application.

Often we aren't so much interested in the throughput of a link as the "end-to-end throughput" between two applications communicating over a path consisting of multiple links and routers. End-to-end throughput can be affected by the lowest transmission rate of the links on the path; the path error rate, packet re-ordering, latency and jitter affecting the TCP congestion-control algorithm; the path MTU and packet re-ordering affecting operating system efficiency; the choice of TCP congestion control algorithm used.

why do we consider transmission delay

We usually don't. We used to, since getting a 1.5KB of packet onto the wire took some time at 9600bps. But at the high data rates in modern networks the number is so small as to be safely ignored outside of weird situations.

Shouldn't we also consider the propagation delay?

Also called "latency". Latency remains important as it's the one performance factor in a global network which isn't improving rapidly. As everything else improves then avoiding latency becomes increasingly important to improving performance. This has effects from avoiding round-trips packet exchanges in application and protocol designs; fielding new protocols which move data closer to their endpoint; and architectural responses such as content distribution networks.

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Transmission rate is not same as bandwidth. Channel Bandwidth – the range of signal bandwidths allowed by a communication channel without significant loss of energy (attenuation). Channel Capacity or Maximum Data rate – the maximum rate (in bps) at which data can be transmitted over a given communication link, or channel.

A typical method of performing a measurement is to transfer a 'large' file from one system to another system and measure the time required to complete the transfer or copy of the file. The throughput is then calculated by dividing the file size by the time to get the throughput in megabits, kilobits, or bits per second.

From the definition I would say they would be considering propagation delay also.

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  • Why do you compute thourghput this way? I would say that file time/size = bandwidth. It is throughput only if you watch realtime movie which does not load your channel to the max. From the definition I would say they would be considering propagation delay also makes no sense. – Valentin Tihomirov Mar 23 '16 at 12:13
  • @ValentinTihomirov You mistyped. Correct - "size/time = bandwidth" – mmv-ru Jul 22 '16 at 16:28

A lot depends on the protocols you are using.

For instance, if you are using a protocol that has some sort of end to end flow control (e.g. TCP) then the latency end to end will could have an effect on throughput. This effect is referred to as the BDP (bandwidth delay product - Google it).

Another answer to your question could be considered where you have a sub-rate service from a provider. The provider runs a fibre to your premise, this fibre could be a 1Gb/s Ethernet link. However, you contract for a 200Mb/s service. So your transmission rate is 1Gb/s, as that's the speed the bits are being sent, but your bandwidth is still 200Mb/s. This is normally controlled with a policer (if you the provider), or a shaper (if you are the subscriber).

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bandwidth or throughput is / where implied - data is received by destination and frequently implied - data is application data (at least L2 or upper) All protocol overhead count there.

transmission rate or bitrate is similar, but data just transmitted but no warranty on receiving by destination. And it not count protocol overhead. It L1 speed.

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