Terms

• Transmission delay

Amount of time transmitting data. Measured from when the first bit of data is pushed on the wire to the when last bit of data is pushed on the wire.

• Propagation delay

Time a single bit spends traversing the link. Measured as how long it takes to travel the distance of the wire at approximately the speed of light.

• Round-Trip Time (RTT)

Total time for a packet to reach destination and a response to return to the sender

• Bandwidth (capacity)

Amount of data sent (or received) per unit time. Measured in bits/time.

• transmission delay vs propagation delay

transmission delay

In a network based on packet switching, transmission delay (or store-and-forward delay) is the amount of time required to push all of the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link.
Transmission delay is a function of the packet's length and has nothing to do with the distance between the two nodes. This delay is proportional to the packet's length in bits,

propagation delay

The time required for a signal to pass through a given complete operating circuit
The time it takes to transmit a signal from one place to another. Propagation delay is dependent solely on distance and two thirds the speed of light

http://in.answers.yahoo.com/question/index?qid=20090218195707AA8qyoK

Propagation delay is how long it takes one bit to travel from one end of the "wire" to the other (it's proportional to the length of the wire, crudely).
Transmission delay is how long it takes to get all the bits into the wire in the first place (it's packet_length/data_rate).
http://stackoverflow.com/questions/17868153/propagation-delay-vs-trasmission-delay