If a certain event occurs every 20 milliseconds (ms) then how many times does it occur each second?~
  20~
  200~
  5000~
  500
~+  50
~~
Network data rates are often described in terms such as Mbit/s, Kbit/s, Gbit/s. If a network's speed is given as 10 Mbit/s how long does it take to send 1000 bits?~
  100 milliseconds~
  1000 milliseconds~
  1000 microseconds
~+  100 microseconds
~+  0.1 milliseconds
~~
Signal propagation speed is usually expressed in terms of m/s or km/s. What is the speed of light in a vacuum?~
   186000 km/s
~+   300000 km/s~
   300000 m/s~
   186000 ft/s
~~
In wires or optical fibers signals travel slower than in a vacuum, and we often use 200,000 km/s as a
rough estimate. Using this estimate how long does it take a signal to travel 5,000 km (approximately
the distance across the US)?
~+ 25ms
~~
When light (or electrical signals) travels in a guided medium 
its speed is ~
  the same as in free space
~+  less than in free space~
  greater than in free space
~~
What is the usual cause of queueing delay in packet switched networks?
~+  More than one packet is ready to be sent on a link at a given time~
  Links break down and can't be used for awhile~
  Packets have to traverse multiple links to get to their destination~
  Some packets are more important than other packets and go to the head of the line