1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Networking speed

  1. Oct 2, 2009 #1
    1. The problem statement, all variables and given/known data

    I would like to send a packet of size 1500 kilobytes from point A to
    point B. There are a total of 3 links that it has to cross, of length 1000,
    2000, 3000m respectively. The bandwidth on those links is 100, 1000,
    and 500 kilobytes/second. Assume that there is no processing time,
    but they have to wait about 1 second at each intermediate router due
    to congestion. Assuming that a bit travels at about half the speed of
    light in the medium, and that a router must have the entire packet
    before it can process it, how long must I wait to get my packet?

    2. Relevant equations

    3. The attempt at a solution

    I'm just trying to see if I'm understanding this correctly.

    If Router A to Router B has a 1000m physical link with a bandwidth of 100 KB per second, then it takes 1 second to push 100 KB of data on to the physical line (of 1000m length). Once it is pushed on the physical line, and I have calculated that one bit takes 0.0000067 seconds to travel 1000m, that 100 KB of data takes 0.0000067 seconds to travel to Router B (which is 1000m away).

    There is 1 second in congestion delay so it'd take 2 seconds (one second to push it on the line and one second in queue) + 0.0000067 seconds of physical travel tie for every 100 KB of data from Router A to Router B. So total time from A to B is 15 * (2 + 0.0000067) seconds.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted