Lecture 6: Facebook & IGP

Question 1

What kind of networking system does facebook use?

Answer 1

A singular administrative control

(one autonomous system)

Question 2

What is the first assumption of the cause for the FB being taking offline?

Answer 2

DNS

Question 3

How do we know that DNS was not the cause of shut down?

Answer 3

The underlying IP address should have been reachable directly.

FBs began to become unresolvable

Question 4

What caused FB shut down?

Answer 4

They accidentally withdrew all their routes

Question 5

How did they fix the BGP?

Answer 5

Relied on system admins and onsite network engineers to update the routing software at each FB datacenter

Question 6

What was the first protocol developed for IGP routing?

Answer 6

Distance-vector protocols

Question 7

What type of protocol has distance-vector lost favor to over the years?

Answer 7

link-state protocols

Question 8

What benefit did distance vectors have for when hardware had limited memory and access speed?

Answer 8

Didnt require that routers keep full maps of the network topology

Question 9

What is the algorithm that is the core of Distance-Vector protocols?

Answer 9

Bellman Ford algorithm

Question 10

What is the bellman ford algorithm

Answer 10

Determines the shortest path in a weighted graph

Question 11

What are the 4 steps of bellman ford?

Answer 11

1. assign infinite cost to getting to every vertex in the graph
2. From the starting vertex, calculate costs to get to neighboring vertices based on the edge weight
3. Recalculate vertex costs as necessary when new paths to that vertex lower the cost to get there
4. After N-1 repetitions (n=# of nodes) the weights are properly assigned

Question 12

What is the oldest IGP protocol?

Answer 12

RIP

Question 13

How does RIP protocol work?

Answer 13

Uses 1 metirc - The hop count

Each edge in the RIP graph has a cost of one, so the total number of edges traversed = total number of hops