You are building a communication network based on RFC 1149 "IP over avian carrier". You attach two 128GB flash drives to your pigeon. You can write data to the flash drive at the rate of 20 MB/s and you can read data from the flash drive at the rate of 50MB/s. The flying speed of a pigeon is 80km/h and pigeons do not need to stop for food or rest before reaching destination. Under what conditions would IP over avian carrier have a lower propagation delay or transmission delay than using the Internet? Explain your answer.
Try an answer before revealing the guidance below.
Key Concepts
- Propagation speed of signals vs pigeon
- Transmission rate of flash writes
- Large data volume
- Effective throughput
Answer Approach
- Compare the “propagation speed” of a pigeon with signal speed in a cable.
- Treat writing to the flash drive as the pigeon link’s transmission rate.
- Compare that rate with the Internet link rate.
- Consider how the answer changes with file size.
Full Answer
Answer status: Draft answer (unofficial). Revision notes, not an official marking scheme.
Propagation delay: practically never — a pigeon at 80 km/h is vastly slower than signals at about 2 × 10^8 m/s, so avian propagation delay is always far higher (unless the Internet path is extremely long or detoured). Transmission delay: the pigeon’s “transmission rate” is the flash write rate, 20 MB/s = 160 Mb/s per drive (320 Mb/s if both drives are written in parallel). If the Internet access link is slower than this, putting the file “onto the link” is faster by pigeon. For very large files (up to 256 GB per flight) on a slow Internet connection, the pigeon’s total delay can also be lower, because the fixed flight time is spread over a large volume of data while Internet transfer time grows with file size.
Pigeon wins if F/R_internet > F/R_write + d/v_pigeon + F/R_readShortcuts: K concepts · A approach · F answer · R reviewed · B bookmark · ← / → previous / next