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

Question List

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 IPv4 datagram.

2. The source IP address is 189.183.188.17

3. The destination IP address is 48.170.183.200

4. Yes, the datagram is encapsulated.

5. The source address of this encapsulated datagram is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

6. The destination address of this encapsulated datagram is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

7. The datagram is an IPv4 datagram.

8. The source IP address is 189.183.188.17

9. The destination IP address is 48.170.183.200

10. Yes, the datagram is encapsulated.

11. The source address of this encapsulated datagram is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

12. The destination address of this encapsulated datagram is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

13. The datagram is an IPv4 datagram.

14. The source IP address is 189.183.188.17

15. The destination IP address is 48.170.183.200

16. Yes, the datagram is encapsulated.

17. The source address of this encapsulated datagram is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

18. The destination address of this encapsulated datagram is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

19. The datagram is an IPv4 datagram.

20. The source IP address is 189.183.188.17

21. The destination IP address is 48.170.183.200

22. Yes, the datagram is encapsulated.

23. The source address of this encapsulated datagram is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

24. The destination address of this encapsulated datagram is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

25. The datagram is an IPv4 datagram.

26. The source IP address is 189.183.188.17

27. The destination IP address is 48.170.183.200

28. Yes, the datagram is encapsulated.

29. The source address of this encapsulated datagram is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

30. The destination address of this encapsulated datagram is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

31. The datagram is an IPv6 datagram.

32. The source IP address is AED9:AD68:8976:EF6A:1139:BC68:AB58:4495

33. The destination IP address is AF11:9DC1:FD24:EF1D:F9D3:DF48:9D83:D943

34. No, the datagram is NOT encapsulated.

35. The tunnel entrance is router F

36. The tunnel exit is router C

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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