Interactive end-of-chapter exercises


Learning Switches - Basic

Consider the LAN below consisting of 10 computers connected by two self-learning Ethernet switches. (You may want to re-read section 6.4.3 in the 8th edition textbook). At t=0 the switch table entries for both switches are empty. At t = 1, 2, 3, and 4, a source node sends to a destination node as shown below, and the destination replies immediately (well before the next time step).

Assume that the following transmissions occur (the transmissions in reply occur but are not shown in the list below):

   t=1: E -> A
   t=2: H -> B
   t=3: E -> H
   t=4: L -> F

Fill out the two switch tables and answer the questions below.



Question List


1. At t=1, what is the source entry for switch 1? Format your answer as letter,number or 'n/a'

2. At t=1, what is the destination entry for switch 1? Format your answer as letter,number or 'n/a'

3. At t=1, what is the source entry for switch 2? Format your answer as letter,number or 'n/a'

4. At t=1, what is the destination entry for switch 2? Format your answer as letter,number or 'n/a'

5. At t=2, what is the source entry for switch 1? Format your answer as letter,number or 'n/a'

6. At t=2, what is the destination entry for switch 1? Format your answer as letter,number or 'n/a'

7. At t=2, what is the source entry for switch 2? Format your answer as letter,number or 'n/a'

8. At t=2, what is the destination entry for switch 2? Format your answer as letter,number or 'n/a'

9. At t=3, what is the source entry for switch 1? Format your answer as letter,number or 'n/a'

10. At t=3, what is the destination entry for switch 1? Format your answer as letter,number or 'n/a'

11. At t=3, what is the source entry for switch 2? Format your answer as letter,number or 'n/a'

12. At t=3, what is the destination entry for switch 2? Format your answer as letter,number or 'n/a'

13. At t=4, what is the source entry for switch 1? Format your answer as letter,number or 'n/a'

14. At t=4, what is the destination entry for switch 1? Format your answer as letter,number or 'n/a'

15. At t=4, what is the source entry for switch 2? Format your answer as letter,number or 'n/a'

16. At t=4, what is the destination entry for switch 2? Format your answer as letter,number or 'n/a'




Solution


1. At time t=1, (E,5) is added as an entry to switch table 1.

2. At time t=1, (A,1) is added as an entry to switch table 1.

3. At time t=1, (E,8) is added as an entry to switch table 2.

4. At time t=1, switch table 2 doesn't observe this frame

5. At time t=2, (H,7) is added as an entry to switch table 1.

6. At time t=2, (B,2) is added as an entry to switch table 1.

7. At time t=2, (H,11) is added as an entry to switch table 2.

8. At time t=2, (B,8) is added as an entry to switch table 2.

9. At time t=3, since the entry for computer E in switch table 1 already exists, no new table entry is made

10. At time t=3, since the entry for computer H in switch table 1 already exists, no new table entry is made

11. At time t=3, since the entry for computer E in switch table 2 already exists, no new table entry is made

12. At time t=3, since the entry for computer H in switch table 2 already exists, no new table entry is made

13. At time t=4, (L,7) is added as an entry to switch table 1.

14. At time t=4, (F,6) is added as an entry to switch table 1.

15. At time t=4, (L,15) is added as an entry to switch table 2.

16. At time t=4, (F,8) is added as an entry to switch table 2.



That's incorrect

That's correct

The answer was: E,5

Question 1 of 16

The answer was: A,1

Question 2 of 16

The answer was: E,8

Question 3 of 16

The answer was: n/a

Question 4 of 16

The answer was: H,7

Question 5 of 16

The answer was: B,2

Question 6 of 16

The answer was: H,11

Question 7 of 16

The answer was: B,8

Question 8 of 16

The answer was: exists

Question 9 of 16

The answer was: exists

Question 10 of 16

The answer was: exists

Question 11 of 16

The answer was: exists

Question 12 of 16

The answer was: L,7

Question 13 of 16

The answer was: F,6

Question 14 of 16

The answer was: L,15

Question 15 of 16

The answer was: F,8

Question 16 of 16

Try Another Problem

We gratefully acknowledge the programming and problem design work of John Broderick (UMass '21), which has really helped to substantially improve this site.

Copyright © 2010-2022 J.F. Kurose, K.W. Ross
Comments welcome and appreciated: kurose@cs.umass.edu