Interactive Problems, Computer Networking: A Top Down Approach

IPv6 Tunneling and Encapsulation

Consider the network shown below which contains four IPv6 subnets, connected by a mix of IPv6-only routers(shaded blue), IPv4-only routers (shaded red) and dual-capable IPv6/IPv4 routers (shaded blue with red interfaces to IPv4 routers). You might want to review Section 4.3.4 in the textbook before doing this problem.

Suppose that a host of subnet A wants to send an IPv6 datagram to a host on subnet F. Assume that the forwarding between these two hosts goes along the path: A --> C --> a --> c --> d --> b --> F

Question List

1. Is the datagram being forwarded from A to C an IPv4 or IPv6 datagram?

2. What is the source address of this A to C datagram?

3. What is the destination address of this A to C datagram?

4. Is this A to C datagram encapsulating another datagram? Yes or No.

5. Is the datagram being forwarded from C to a an IPv4 or IPv6 datagram?

6. What is the source address of this C to a datagram?

7. What is the destination address of this C to a datagram?

8. Is this C to a datagram encapsulating another datagram? Yes or No.

9. What is the source address of this encapsulated datagram?

10. What is the destination address of this encapsulated datagram?

11. Is the datagram being forwarded from a to c an IPv4 or IPv6 datagram?

12. What is the source address of this a to c datagram?

13. What is the destination address of this a to c datagram?

14. Is this a to c datagram encapsulating another datagram? Yes or No.

15. What is the source address of this encapsulated datagram?

16. What is the destination address of this encapsulated datagram?

17. Is the datagram being forwarded from c to d an IPv4 or IPv6 datagram?

18. What is the source address of this c to d datagram?

19. What is the destination address of this c to d datagram?

20. Is this c to d datagram encapsulating another datagram? Yes or No.

21. What is the source address of this encapsulated datagram?

22. What is the destination address of this encapsulated datagram?

23. Is the datagram being forwarded from d to b an IPv4 or IPv6 datagram?

24. What is the source address of this d to b datagram?

25. What is the destination address of this d to b datagram?

26. Is this d to b datagram encapsulating another datagram? Yes or No.

27. What is the source address of this encapsulated datagram?

28. What is the destination address of this encapsulated datagram?

29. Is the datagram being forwarded from b to F an IPv4 or IPv6 datagram?

30. What is the source address of this b to F datagram?

31. What is the destination address of this b to F datagram?

32. Is this b to F datagram encapsulating another datagram? Yes or No.

33. What is the source address of this encapsulated datagram?

34. What is the destination address of this encapsulated datagram?

35. What router is the 'tunnel entrance'? Give the router's letter

36. What router is the 'tunnel exit'? Give the router's letter

37. Which protocol encapsulates the other, IPv4 or IPv6?

Solution

1. The datagram is an IPv6 datagram.

2. The source IP address is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

3. The destination IP address is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

4. No, the datagram is NOT encapsulated.

5. The datagram is an IPv4 datagram.

6. The source IP address is 56.243.136.102

7. The destination IP address is 212.244.128.177

8. Yes, the datagram is encapsulated.

9. The source address of this encapsulated datagram is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

10. The destination address of this encapsulated datagram is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

11. The datagram is an IPv4 datagram.

12. The source IP address is 56.243.136.102

13. The destination IP address is 212.244.128.177

14. Yes, the datagram is encapsulated.

15. The source address of this encapsulated datagram is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

16. The destination address of this encapsulated datagram is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

17. The datagram is an IPv4 datagram.

18. The source IP address is 56.243.136.102

19. The destination IP address is 212.244.128.177

20. Yes, the datagram is encapsulated.

21. The source address of this encapsulated datagram is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

22. The destination address of this encapsulated datagram is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

23. The datagram is an IPv4 datagram.

24. The source IP address is 56.243.136.102

25. The destination IP address is 212.244.128.177

26. Yes, the datagram is encapsulated.

27. The source address of this encapsulated datagram is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

28. The destination address of this encapsulated datagram is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

29. The datagram is an IPv4 datagram.

30. The source IP address is 56.243.136.102

31. The destination IP address is 212.244.128.177

32. Yes, the datagram is encapsulated.

33. The source address of this encapsulated datagram is F8B7:FE58:5DA6:5D11:CD88:6139:325E:DDFC

34. The destination address of this encapsulated datagram is D693:688D:A93C:DE7D:2FD7:E625:CF39:E68C

35. The tunnel entrance is router C

36. The tunnel exit is router F

37. IPv4, in order to maintain compatibility with existing IPv4 infrastructure, IPv6 datagrams are put in the payload of an IPv4 datagram. These IPv4 datagrams are passed on until it reaches a router which supports IPv6, where the IPv6 datagram is decapsulated and passed on.

We greatly appreciate the work of John Broderick (UMass '21) in helping to develop these interactive problems.

Interactive end-of-chapter exercises

IPv6 Tunneling and Encapsulation

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