Let’s consider a scenario, there are two user located in USA and India. They both wish to download recent documentary “Social Dilemma” on Netflix.They both request for download to Netflix server located in India at same time.
Do you think data packets will transfer to both in equal time interval??. They both noticed that guy in USA have to wait for more time than Indian guy to receive data packets. This is due to Latency (Delay) in Internet.
First let’s take some information before coming back to our case study.
Latency or delay defines how long it takes for an entire message to completely arrive at the destination from the time the first bit is sent out from source.
Four types or Delay :
- Transmission Delay :
Time taken to place complete data packet on transmission medium . It solely depend upon bandwidth and message size.
- Propagation Delay :
Time it takes for a bit to go from node A to node B. It depends upon on distance and propagation velocity. Now in our study, American guy is farther away from server as compared to Indian guy. So propagation delay for American guy is more than Indian guy.
- Queing Delay :
Time it takes for each intermediate or end device to hold the message before it can be processed. Data traffic plays a critical factor in this delay. This delay is not fixed and totally depends upon condition of node .
- Processing Delay :
It is simply how much time node takes to process the message it receives.
Now, jumping back to our case study, propagation delay and queing delay are responsible for late packet recieval by American guy as compared to Indian guy.As distance is more between server and American guy, thus propagation delay is more. As it is far away, data packets comes through more number of routers , and each routers may have any number of request already to be processed. Now, routers flow FIFO principle, and thus our packet has to wait until all packet before it is processed by each routers. Thus, queing delay is way more in American guy data transfer as compared to Indian guy.
Now, next time you experience a buffer on YouTube, you know reason behind it!!