F1.3/4 Naming/Coordination

Question 1

What are some examples of Flat naming?

Answer 1

Broadcasting
Forwarding Pointer
Home-based approach

Question 2

Explain broadcasting naming

Answer 2

Request entity to return its current location (for example ARP)

Drawbacks: Cannot scale beyond LAN

Question 3

Explain Forwarding pointer and one drawback with it

Answer 3

When the entity moves, it leaves a pointer to next location

Drawback: Geographical scalability problems, too long chain of pointers introduce problems

Question 4

Explain home-based approach

Answer 4

Let a “home” keep track of where an entity is. If someone wants to connect to entity, first connect to the “home” and because the home knows where the entity is, it forwards the request to the entity.

Question 5

What is the problem with physical clocks? And whats the solution

Answer 5

Problem: We need the exact time
Solution: Universal Coordinated Time (UTC)

Question 6

What’s Internal- and External synchronization?

Answer 6

Internal: Keep clocks precise
External: Keep clocks accurate

Question 7

What’s the berkely algorithm?

Answer 7

Let time server scan machines, calculate the average time of all machines and inform each machine on how to correct their time.

Question 8

What does logical clocks do?

Answer 8

Count number of events that occurred instead of time elapsed.

Question 9

Explain lamports logical clocks

Answer 9

Each process has a counter Ci , for each happening of that process, the counter increments. Attach the the Ci or t to each message to sync the system

Question 10

What an assumption of Total-ordered multicast?

Answer 10

Communication is reliable and that we are using FIFO