Delay and the HTTP

• Calculate the time it takes to download a page. NYTimes home page
  • Recall that total delay is: $d_{proc} + d_{queue} + d_{trans} + d_{prop}$
    • Lets ignore $d_{proc}$ and $d_{queue}$
  • What are all of the components of a page that we need to keep in mind:
    • How many images? 47 images each ~50k
    • javascript files 10 javascript @ 93k each
    • css files 10 css files @ 20k each
    • initial page is 173k
  • What other factors are important?
    • assuming terrestrial link at 8Mbps
    • propagation delay of 5000km at 2.4e8 m/s
    • assuming that the connection is closed after each request
  • Use this notebook to compute the total delay for the page to be loaded.

• Redo the calculation for this page, but assume that the connection is through a satellite link.
  • Distance to satellite is 35786e3 meters

Now, there are many ways that the process can be speeded up. Not having to reopen a connection for every request is certainly one of them.

• Redo the calculations assuming that we can keep the connection open.
• How might we really speed up the process?
  • use a local cache
  • redo the calculations