## NPTEL Advanced Computer Networks Week 2 Assignment Answers 2024

1. Given a destination address of 11101000 in a binary trie, what is the first step during the IP lookup?

- Traverse to the left
- Traverse to the right
- Randomly choose to move left or right
- Alternate between left and right traversal

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2. Consider the prefix database table shown below; how many fewer nodes will be needed to represent a path-compressed trie compared to a 1-bit binary trie?

- 0
- 2
- 3
- 4

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3. Which among the following is true when the trie constructed with a set of prefixes resulted into a full binary tree?

- Only binary trie has the best lookup and update complexity
- Only path compressed trie has the best lookup and update complexity
- Both binary and path-compressed tries have the same lookup and update complexity
- Binary trie and path-compressed tries have the same lookup complexity but different update complexity

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4. Consider the prefix database table shown below; what is the height of the trie constructed using a 1-bit binary trie?

**Note: The height of the root node (P1) is 1.**

- 6
- 7
- 8
- 9

Answer :-

5. Consider the following scenarios for how the DIR-24-8 algorithm performs route lookups using two tables. Assume the routes listed below are already in the table: 10.54/16 (1), 10.54.34/24 (2), and 10.54.34.192/26 (3). The first route requires entries in TBL24 (First Table), while the second and third routes require entries in TBLlong (Second Table). Which of the following statements is/are correct based on the above scenario?

- If a packet arrives with the destination address 10.54.22.147, the table will return an entry with the correct next hop (1).
- If a packet arrives with the destination address 10.54.34.23, the table will return an entry with the correct next hop (2)
- If a packet arrives with the destination address 10.54.34.15, the table will return an entry with the correct next hop (1)
- If a packet arrives with the destination address 10.54.39.128, the table will return an entry with the correct next hop (1)

Answer :-

6. Given the prefix table provided below, identify which prefixes should be combined to minimize the table size for efficient storage in TCAM.

- P1 and P4
- P1 and P5
- P2 and P3
- P4 and P6

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7. What is the overall storage complexity for the binary trie structure in terms of the number of prefixes (N) and the maximum length of the prefix (W)?

- O(W)
- O(N)
- O(NW)
- O(N
^{2})

Answer :-

8. How are route prefixes longer than 24 bits handled in the DIR-24-8-BASIC algorithm

- Stored directly in TBL24
- Utilize a separate table, TBLlong, with pointers from TBL24
- Merged with shorter prefixes for compact storage
- Increasing the width of memory entries

Answer :-

9. Consider the prefix database table shown below; what is the skip value for node P5 and the segment for node P9 when a trie is constructed using path-compressed technique?

- Skip: 3 and Segment: 01
- Skip: 1 and Segment: 1010
- Skip: 2 and Segment: 101
- Skip: 2 and Segment: 010

Answer :-

10. In the TCAM device, the IP address 192.131.76.84 yields matches at various memory locations: 4012, 2535, 1035, and 536. When confronted with multiple matches, the priority encoder determines the output based on the highest priority. Which memory location is prioritized by the priority encoder in case of multiple matches?

- 536
- 1035
- 2535
- 4012

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