How to Calculate Network Traffic Throughput – Networking Guide

networking

I came across this question in a textbook, but there are no solutions and I'm not sure how to solve this.

The question is: Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three links of rates R1=500Kb/s, R2=2Mb/s and R3=1Mb/s. Assuming that there is another busy flow that travels through the same set of links (say from Host C to Host D), what will be the throughput for this file transfer?

I know that the throughput for no traffic would be the min(R1, R2, R3), so would the throughput with traffic be the max(R1, R2, R3)?

Best Answer

 Speed = min(R1,R2,R3) / number_of_connections

Related Solutions

Web Applications Networking – Calculate Web-Application Acceptable Use Bandwidth

In the past I have approached problems like this by minimizing latency either on the client side or on the server side. Knowing the size of the network pipe is one thing, but it usually something that you cannot modify. Usually, with a centralized server, it is the server that is the issue.

Although quite a bit is left to judgement, there are some approximations.

    Wide area network 100s of millisec
    Disk access 10 milli sec
    Ssd disk access .5 milli sec
    Local area network, .5 mill sec
    Local memory 100 nano sec
    Processor Cache  100 pico sec

So consider what basic steps you web app has to do and tally the up. See how close you are - either you have forgotten something ( most likely), or you need to modify your approximations.

For example, there was a web application that I was working on that most requests took a bit more than 70 ms to respond. I traced this to 7 database operations. A Proposal to increase performance was to cache more data locally (we were hitting a couple of static tables that could be cached locally), bringing the latency down to bit more than 50 ms. Furthermore, by going with SSDs, we could potentially bring it down a bit more 5 ms. Of, course lower latency means that the server can handle a higher peak load.

Networking – Can Someone Implement a Custom Network Protocol

That's exactly the problem – intermediary routers may not understand new protocols and only forward IP packets if they look like UDP or TCP that they understand.

There are actually many extensions to the TCP protocol to make it more performant, but takeup by routers has been slow.

If a new protocol is created, it will need to sit on top of an existing protocol. Because many of TCP's convenience features are undesirable for a new protocol (in particular, the particular congestion control mechanisms, head-of-line blocking, and the three-way handshake), this means that new protocols will typically extend UDP. However, UDP has its own share of problems with regards to NAT traversal, because it is a connectionless protocol.

As an example of a new protocol that sits on top of UDP, consider the QUIC protocol. It is intended as a more performant TCP, and is used widely in the Google ecosystem. For more details consider reading QUIC as a solution to protocol ossification on LWN.

New protocols on top of IP can only be used reliably if you control the network in which they are used. However, you can still use tunnelling to use these protocols over the public internet (i.e., through a VPN).

Best Answer

Related Solutions

Web Applications Networking – Calculate Web-Application Acceptable Use Bandwidth

Networking – Can Someone Implement a Custom Network Protocol

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