Note: These exercises are quite simple but be sure to be careful about the difference between bits and bytes (8 bits make a byte) and seconds, milliseconds (1/1000 sec), and microseconds (1/1,000,000 sec). The notation 30ms means 30 milliseconds.

Note: Be careful whether distances are reported as meters (such as distances on a campus or within a building) or in kilometers (km) such as distances between cities!!

Note: In these exercises, there are questions asking transmission delay. This means just the time to send x bits at y bits/sec. It does not include real-world complexities like acknowledgements, router delays etc. We call it "transmission delay" rather than "transmission time" to indicate that this is the delay due to transmission, not the total time counting all kinds of delays.

Note: Times should all be reported as decimal numbers, not fractions. Thus an answer should be .001 seconds (or 1 ms), NOT 1/1000 sec.

1. How many bits are in a packet with 55,000 bytes? ___________________________

2. The Ethernet to most machines on campus is 100Mbps (100 million bits/sec). What is the transmission delay to send a huge file of 50,000,000 bytes (50 Mbytes).

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3. Using a 100Mbps Ethernet, what is the transmission delay for a music file of 10Megabytes (10 million bytes)?

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4. What is the transmission delay for a packet of 1000 bytes if the link speed is 10,000 bits/sec?

   _______________________________

5. Assuming propagation speed of 2 x 10⁸ meters/sec, what is the propagation delay for a link 100 meters (across campus)? (Be sure to indicate if your answer is in seconds, ms, or microseconds).

   ______________________________________________

6. Using the propagation speed above, what is the propagation delay for a link of 10,000 km? (km = kilometer, 1000 meters)

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7. Using the approximate propagation speed above, what is the propagation delay to send from Canton to Bangalore, India?

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8. We are sending a packet though a network with 4 nodes, each with a nodal processing time of 1/100 ms. There are 3 links. One is 100 meters, one is 1000 km, and the other is 100 meters. (Propagation speed is 2 x 10⁸ meters/sec) The first link is 100Mbps, the second is 10Mbps, and the third is 100Mbps. Assuming no queuing or other router delay, what is the total time needed to send a 500,000 byte file from the first node to the last? Times you know are MUCH smaller than others may be reported as "trivial".

   Nodal delay total: _____________________________

   Link 1: Propagation: __________________ Transmission: __________________

   Link 2: Propagation: __________________ Transmission: __________________

   Link 3: Propagation: __________________ Transmission: __________________

   Total: ____________________________ (to 2 significant figures only)

   link 1 link 2 link 3 NODE1------------NODE2-------------NODE3------------NODE4