homework1 - Dept. of Computer Science HKUST CSIT 561...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Dept. of Computer Science HKUST CSIT 561 Computer Networks: An Internet Perspective Fall Semester 2009 Homework 1 Due Date: Sunday 27 Sep. 2009 11:59 pm Submission Instructions: Please submit your solutions electronically through the LMES website http://lmes2.ust.hk . Please go the CSIT 561 website and look under Assignments. You will see Homework 1 listed there. Please submit your work either in PDF format (preferred), or MS Word format. Problems: 1. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m metres, and suppose the propagation speed along the link is s metres/ sec. Host A is to send a packet of size L bits to host B. a) Express the propagation delay, d prop , in terms of m and s . d prop = length of physical link / propagation speed in medium = m/s sec b) Determine the transmission time of the packet, d trans , in terms of L and R . d tran = packet length / link bandwidth = L/R sec c) Ignoring processing and queuing delays, obtain an expression for the end-to-end delay. End-to-end delay = d prop + d tran = m/s + L/R sec d) Suppose host A begins to transmit the packet at time t = 0 . At time t = d trans , where is the last bit of the packet? The last bit of the packet is just leaving the host A. CSIT 561 (Fall 2009) Homework 1 1
Background image of page 1

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

View Full DocumentRight Arrow Icon
Dept. of Computer Science HKUST e) Suppose d prop is greater than d trans . At time t = d trans , where is the first bit of the packet? The first bit of the packet leaves the host A and does not reach the host B. It is on the physical link. f) Suppose d prop is less than d trans . At time t = d trans , where is the first bit of the packet? The first bit of the packet arrivals at host B. g) Suppose s = 2.5 × 10 8 , L = 100 bits, and R = 28 Kbps. Find the distance m so that d prop equals d trans . d prop = d tran => m/s = L/R => m = L/R*s => m = 100bit / 28Kbps * 2.5*108 => m = 892.86 km h) Use a program like Microsoft Excel to explore the interplay of transmission and propagation delay further. Consider three different packet sizes L = 100 bits, 1000 bits and 1,000,000 bits. Further consider three different link bandwidths R = 56 Kbps, 1.5 Mbps and 1.5 Gbps. Also, consider three different distances m = 2.5 metres, 25 Km, and 2500 Km. For each of these 27 combinations, compute d prop , d trans and the end-to-end delay. Explain your observations in a few sentences. L R m d prop d tran end-to-end 100 56000 2.5 1.00E-08 0.001786 0.00178572 100 56000 25000 0.0001 0.001786 0.00188571 100 56000 2500000 0.01 0.001786 0.01178571 100 150000 0 2.5 1.00E-08 6.67E-05 6.67E-05 100 150000 25000 0.0001 6.67E-05 0.00016667 CSIT 561 (Fall 2009) Homework 1 2
Background image of page 2
Dept. of Computer Science HKUST 0 100 150000 0 2500000 0.01 6.67E-05 0.01006667 100 1.5E+09 2.5 1.00E-08 6.67E-08 7.67E-08 100 1.5E+09 25000 0.0001 6.67E-08 0.00010007 100 1.5E+09 2500000 0.01 6.67E-08 0.01000007 1000 56000 2.5 1.00E-08 0.017857 0.01785715 1000 56000 25000 0.0001 0.017857 0.01795714 1000 56000 2500000 0.01 0.017857 0.02785714 1000 150000 0 2.5 1.00E-08 0.000667 0.00066668 1000 150000 0 25000 0.0001 0.000667 0.00076667 1000 150000 0 2500000 0.01 0.000667 0.01066667 1000 1.5E+09 2.5 1.00E-08 6.67E-07 6.77E-07 1000 1.5E+09 25000 0.0001 6.67E-07 0.00010067 1000 1.5E+09 2500000 0.01 6.67E-07 0.01000067 100000 0 56000 2.5 1.00E-08 17.85714 17.8571429 100000 0 56000 25000 0.0001 17.85714 17.8572429 100000 0 56000 2500000 0.01 17.85714 17.8671429 100000 0 150000 0 2.5 1.00E-08 0.666667 0.66666668 100000 0 150000 0 25000 0.0001 0.666667 0.66676667 100000 0 150000 0 2500000 0.01 0.666667 0.67666667 100000 0 1.5E+09 2.5 1.00E-08 0.000667 0.00066668 100000 0 1.5E+09 25000 0.0001 0.000667 0.00076667 100000 0 1.5E+09 2500000 0.01 0.000667 0.01066667
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/21/2009 for the course CSE csit561 taught by Professor Zq during the Spring '09 term at HKUST.

Page1 / 18

homework1 - Dept. of Computer Science HKUST CSIT 561...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online