Lecture 9 - Communication III and Lecture 10 - Naming I

Question 1

In epidemic (Gossip-based) protocol:

a) Node forwards message to a randomly chosen neighbor
b) Node forwards message to all their neightbors

Answer 1

a) Node forwards message to a randomly chosen neighbor

Question 2

Overlay network is formed by:

a) Network routers
b) Application layer processes

Answer 2

b) Application layer processes

Question 3

When using flooding multicasting model:

a) Node forwards message to a randomly chosen neighbor
b) Nodes forwards message to all their neighbors

Answer 3

b) Nodes forwards message to all their neighbors

Question 4

How many messages can be sent in an ALM of N processes with a mesh topology?

a) N-1
b) 1/2 * N * N-1

Answer 4

b) 1/2 * N * N-1

Question 5

What is the major challenge in flooding-based multicasting?

a) Redundant and excessive messages in the network
b) Network outages
c) Not fault tolerant

Answer 5

a) Redundant and excessive messages in the network

Question 6

Which overlay network topology is more efficient in the number of messages sent in the network?

a) Tree topology
b) Mesh toplogy

Answer 6

a) Tree topology

If G is a tree, we’ll send M = N-1 messages (Optimal situation)

Question 7

Which overlay network is more robust and fault-tolerant for routing messages?

a) Tree topology
b) Mesh topology

Answer 7

b) Mesh topology

If G is fully connected (mesh), we’ll send M = ½ . N . (N-1)
messages (worst-case)

Question 8

In gossip-based protocols, which of the nodes initiates a pull update?

a) Infectious node
b) Susceptible node
c) Removed node

Answer 8

b) Susceptible node

Question 9

Un gossip-based protocols, which of the nodes initiates a push update?

a) Susceptible node
b) Infectious node
c) Removed node

Answer 9

b) Infectious node

Question 10

What are some characteristics of FLAT NAMING?

Answer 10

• Entities are refered to by an ifentifier/name with no meaning
• It bears no structure
  *e.g. MAC or memory adresses

Question 11

What is the core issue of FLAT NAMING?

Answer 11

Needs special mechanisms to trace the location of refered entities

Question 12

What are some approaches for searching/resolving a name/identifier of an entity to its adress in regards to FLAT NAMING?

Answer 12

• Broadcasting
• Chains of forwarding links
• Home-based approach
• Distributed Hash Tables
• Hierachical Location services