Assignment 6

Due March 9, 2016 6:55pm via sakai

Introduction

Please answer the questions precisely and concisely. Every question can be answered in one or at most a few sentences. I will not have the patience to read long paragraphs or essays and you may lose credit for possibly correct answers.

Submit your work via sakai as a plain text or pdf document. No Microsoft Word, Apple Pages, ePub, et cetera formats.

Reading

Text: Sections 3.5 (Connection-Oriented Transport: TCP) through 3.7 (the end of Fast Recovery) pages 230–277

Questions

(1a,b) [Kurose & Ross text: page: 288, question R15] Suppose Host A sends two TCP segments back to back to Host B over a TCP connection. The first segment has sequence number 90; the second has sequence number 110.

(1a). How much data is in the first segment?

(1b). Suppose that the first segment is lost but the second segment arrives at B. In the acknowledgment that Host B sends to Host A, what will be the acknowledgment number?

(2a,b,c,d) [Kurose & Ross text: page: 288, question P3]
Note: the text poses a number of questions in this problem and does not divide them into individual sections. Please associate your answers clearly with each sub-part.

UDP and TCP use 1s complement for their checksums. Suppose you have the following three 8-bit bytes:

01010011
01100110
01110100

(2a) What is the 1s complement of the sum of these 8-bit bytes? (Note that although UDP and TCP use 16-bit words in computing the checksum, for this problem you are being asked to compute 8-bit sums.) Show all work.

(2b) Why is it that UDP takes the 1s complement of the sum; that is, why not just use the sum? With the 1s complement scheme, how does the receiver detect errors? (These two questions share a common answer.)

(2c) Is it possible that a 1-bit error will go undetected?

(2d) How about a 2-bit error?

(3) [Kurose & Ross text: page: 290, question P15]
Consider the cross-country example shown in Figure 3.17. How big would the window size have to be for the channel utilization to be greater than 98 percent? Suppose that the size of a packet is 1,500 bytes, including both header fields and data.

(4) [Kurose & Ross text: page: 295, question P34]
What is the relationship between the variable SendBase in Section 3.5.4 and the variable LastByteRcvd in Section 3.5.5?

(5) [Kurose & Ross text: page: 295, question P3]
What is the relationship between the variable LastByteRcvd in Section 3.5.5 and the variable y in Section 3.5.4?