Interactive end-of-chapter exercises


Supplement to Computer Networking: A Top Down Approach 8th Edition


"Tell me and I forget. Show me and I remember. Involve me and I understand." Chinese proverb

Textbook Cover

Openflow Flow Tables

Consider the 4-router network shown below, where packet forwarding is controlled by flow tables (e.g., configured via OpenFlow in an SDN controller), rather than by a forwarding table computed by a routing algorithm. The addresses of networks attached to each of the router is also shown. The interfaces at each of the routers are also as indicated.


Suppose we want the following forwarding behavior of packets to be implemented:

Complete the match-plus-action tables in each of the routers, s1, s2, s3, and s4, that implement these forwarding behaviors. Your rules should be as strict as possible (should only allow these behaviors, and no other forwarding behaviors). You can assume that any packet arriving at a router that does not match a rule in that table will be dropped.



Question List


1. For router s1, what should the value of the 'IP Src' be? Pick either a specific address (including CIDR), any, or none

2. For router s1, what should the value of the 'IP Dst' be? Pick either a specific address (including CIDR), any, or none

3. For router s1, what should the value of the 'Src Port' be? Pick either a specific port, or any

4. For router s1, what should the value of the 'Dst Port' be? Pick either a specific port, or any

5. For router s1, what should the value of the 'IP Proto' be? Pick either TCP, UDP, or any

6. For router s1, what should the action of the rule be? Some examples include forward, allow, deny, etc

7. For router s1, what interface should the packets be forwarded to?

8. For router s2, what should the value of the 'IP Src' be? Pick either a specific address (including CIDR), any, or none

9. For router s2, what should the value of the 'IP Dst' be? Pick either a specific address (including CIDR), any, or none

10. For router s2, what should the value of the 'Src Port' be? Pick either a specific port, or any

11. For router s2, what should the value of the 'Dst Port' be? Pick either a specific port, or any

12. For router s2, what should the value of the 'IP Proto' be? Pick either TCP, UDP, or any

13. For router s2, what should the action of the rule be? Some examples include forward, allow, deny, etc

14. For router s2, what interface should the packets be forwarded to?

15. For router s4, what should the value of the 'IP Src' be? Pick either a specific address (including CIDR), any, or none

16. For router s4, what should the value of the 'IP Dst' be? Pick either a specific address (including CIDR), any, or none

17. For router s4, what should the value of the 'Src Port' be? Pick either a specific port, or any

18. For router s4, what should the value of the 'Dst Port' be? Pick either a specific port, or any

19. For router s4, what should the value of the 'IP Proto' be? Pick either TCP, UDP, or any

20. For router s4, what should the action of the rule be? Some examples include forward, allow, deny, etc

21. For router s4, what interface should the packets be forwarded to?




Solution


(Q1-Q7) Rule 1. | IP_Src=128.122/16, IP_Dst=128.120/16, Src_Port=Any, Dst_Port=Any, IP_Protocol=Any, Action=Forward(2) |

(Q8-Q14) Rule 2. | IP_Src=128.122/16, IP_Dst=128.120/16, Src_Port=Any, Dst_Port=Any, IP_Protocol=Any, Action=Forward(1) |

(Q15-Q21) Rule 3. | IP_Src=128.122/16, IP_Dst=128.120/16, Src_Port=Any, Dst_Port=Any, IP_Protocol=TCP, Action=Forward(2) |



That's incorrect

That's correct

The answer was: 128.122/16

Question 1 of 21

The answer was: 128.120/16

Question 2 of 21

The answer was: Any

Question 3 of 21

The answer was: Any

Question 4 of 21

The answer was: Any

Question 5 of 21

The answer was: Forward

Question 6 of 21

The answer was: 2

Question 7 of 21

The answer was: 128.122/16

Question 8 of 21

The answer was: 128.120/16

Question 9 of 21

The answer was: Any

Question 10 of 21

The answer was: Any

Question 11 of 21

The answer was: Any

Question 12 of 21

The answer was: Forward

Question 13 of 21

The answer was: 1

Question 14 of 21

The answer was: 128.122/16

Question 15 of 21

The answer was: 128.120/16

Question 16 of 21

The answer was: Any

Question 17 of 21

The answer was: Any

Question 18 of 21

The answer was: TCP

Question 19 of 21

The answer was: Forward

Question 20 of 21

The answer was: 2

Question 21 of 21

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