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Advanced Computer Networks Exam Questions with Correct Answers
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Advanced Computer Networks Exam Questions with Correct Answers
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Advanced Computer Networks ExamQuestions with Correct Answers
What do we want from the network (6)? - Answer-Performance
Reliability
Availability
Security
Flexibility
Manageability
What is bandwidth? - Answer-Max rate of data transfer across a given path
- How many data at a time
What is latency? - Answer-The amount of time it takes to delver some data from src to
dst across the network.
- Time to tranmit 1 byte
What is the bottleneck for large objects during the transfer? - Answer-Bandwidth
What are three possible requirements for network Applications? - Answer--
Performance
- Consistency
- Predictability
What is the end-to-end argument? - Answer-Reliable transmission can only be achieved
with end-to-end implementations
What is the fade-sharing principle? - Answer-End systems fail together or not at all. You
do not keep States on intermediary nodes.
Explain Packet VS Circuit switching - Answer-Packet Switching = Message split up in
packets and send over network individualy.
Circuit Switching = Reserve a line for whole Communication.
What are popular Operations in networking? - Answer-Matching and counting
Why are probabilistic data structures more suitable than deterministic ones? - Answer-
Because they are generally faster and consume less space
, What to do if something is critically important (data structure checks)? - Answer-First
probabilistic for fast negative filtering. Then the deterministic (slower) check will be less
frequent.
Explain the bloom filter: - Answer-We maintain M bit cells. Then we apply a hash
function on incoming data and set the corresponding value to 1.
Only supports "Insert" and "Check".
Often multiple hash functions. Elements is then only considered if ALL the hash values
map to 1.
What are the probabilities in bloom filters?
M = Cells
N = Elements
1. Element to be mapped to cell
2. Element not mapped to a cell
3. Probability of a cell being 0
4. False positive rate - Answer-1. Element to be mapped to cell = 1/M
2. Element not mapped to a cell = 1 - (1/M)
3. Probability of a cell being 0 = (1 - (1/M)) ^ N
4. False positive rate = 1 - ((1 - (1/M)) ^ N)
What are the probabilities in bloom filters with multiple hash functions (K)?
M = Cells
N = Elements
1. Element to be mapped to cell
2. Element not mapped to a cell
3. Probability of a cell being 0
4. False positive rate - Answer-1. Element to be mapped to cell = 1/M
2. Element not mapped to a cell = 1 - (1/M)
3. Probability of a cell being 0 = (1 - (1/M)) ^ NK
4. False positive rate = 1 - ((1 - (1/M)) ^ KN) ^ K
What is the tradeoff space for bloom filters? - Answer-Memory
Number of Operations
False Positive Rate
Name two bloom filter extensions - Answer-1. Counting Bloom Filters
2. Invertible Bloom lookup tables
What is Count Min? - Answer-Multiple Bloom filters.
Value + 1 on hit.
When requesting count, we get all and take the min (most probable true value)
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