Week 6

Question 1

Whats the purpose, process, goals, and features of GOSSIPING?

Answer 1

purpose - disseminate info accross network
process - nodes share info with a few peers, peers spread it
goals - ensure nodes receive the same info eventually, effeciently
features - fast, scalable, no guarantee of agreement (conflicting info is possible)

Question 2

Whats the difference between gossiping and consensus?

Answer 2

gopssing - fast, scalable, nodes share data untill all receive it
consensus - slow, resource-intensive, all nodes musit agree to validity and order of data

Question 3

when to flood vs gossip?

Answer 3

flood - need quick, reliable info to all nodes in network

gossip - fast, scalable communication without need for immediate validation or agreement

Question 4

How should a blockchain react to a 51% attack, sybil attack, ddos?

Answer 4

51 - implement stronger proof of sake, increase cost of attack

sybil - use reputation systems, peer verification to limit malicious nodes

ddos - use rate limiting, distributed nodes, redundancy to mitigate overload

Question 5

why should mining difficulty be recalculated periodically?

Answer 5

• ensures blocks are mined at a consistent rate to balance performance
• good time ensures blocks process transactions effeciently, but not quick enough to be vulnerable to attacks/forks

Question 6

is a blockchain secure?

Answer 6

yes, secure because each block has a unique hash and references previous hash, creating an immutable record. also consensus makes participants agree on a state

Question 7

is the DHT in bittorrent similar to a fancy ring solution?

Answer 7

yes, uses dist. network where peers are organized in a ring-like structure to share files, tracker (known-host) allows users to connect to network, DHT allows peers to locate other sharing same file

Question 8

how does a query work in a ring based system?

Answer 8

when query comes in, passed around the ring and each node checks if it has the relevant data, continues on until found

Question 9

what could the message be in a ring-based query system? what how does it get back?

Answer 9

message typically contains the query itself, target data/result, and metadata like an identifier or timestamp. once correct node is located, it sends response back through same path/reverse route in the ring

Question 10

Whats the cost if a node goes offline in a DHT?

Answer 10

if node goes offline, other nodes may lose access to the data that was stored by that node, so the system would need to reassign that data to another node. also queries would need ot be rerouted, so DHTs usually have replication/backup strategies to maintain performane