434hw1sol

# 434hw1sol - CSE 434 TTh 9:15 AM Homework #1 Sample Solution...

This preview shows pages 1–2. Sign up to view the full content.

CSE 434 – TTh 9:15 AM Homework #1 Sample Solution September 16, 2003 Please email Catherine ( [email protected] ) if you have questions about the sample solution. 1. (1.1) Imagine that you have trained your St. Bernard, Bernie, to carry a box of three 8mm tapes instead of a flask of brandy. (When your disk fills up, you consider that an emergency.) These tapes each contain 7 gigabytes. The dog can travel to your side, wherever you may be, at 18 km/hour. For what range of distances does Bernie have a higher data rate than a transmission line whose data rate (excluding overhead) is 150 Mbps? 1 gigabyte = 2 30 byte = 1 073 741 824 byte A data tape carries 7 GB. Since a dog can carry 3 tapes at a time, he can carry 3*7*(8*2 30 ) bits per load, at a rate of 18 km / hour (or 0.005 km / second). Let x be the distance Bernie travels. We need to determine for what range of distances Bernie have a data rate higher than 150 Mbps (or 150*10 6 bps), that is, ( 29 sec / 10 150 sec 005 . 0 2 8 7 3 6 30 bits xkm km bits × × × × × Solve to obtain x < 6.01km (1.5) A factor in the delay of a store-and-forward packet-switching system is how long it takes to store and forward a packet through a switch. If switching time is 10 microseconds, is this likely to be a major factor in the response of a client-server system where the client is in New York and the server is in California? Assume the propagation speed in copper and fiber to be 2/3 the speed of light in a vacuum ( 3 x 10 8 m/sec ). The distance between SJC airport (San Jose, CA) and JFK airport (New York, NY) is 2968.2 miles (or 4749.1 km). So the time for a signal from client to server (without switching) is ms s 95 09498 . 0 ) 300000000 * 3 2 /( 1000 * 1 . 4749 = = 10 microsecond : 95ms is approximately 1 : 10 4 , so the 10 microsecond switching time to store and forward packets is unlikely to have a significant effect on the response of the client- server system unless thousands of switches occur along the way. The more significant

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This document was uploaded on 04/29/2010.

### Page1 / 5

434hw1sol - CSE 434 TTh 9:15 AM Homework #1 Sample Solution...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online