Tutorial 5

Question 1

What are the properties of a centralized routing algorithm and give an example

Answer 1

• Done between source and destination
• Complete knowledge of global network

Example: Open Shortest Path First (OSPF) which has complete map constructed by each router

Question 2

What are the properties of a decentralized/distributed routing algorithm and give an example

Answer 2

• Done by routers in a more local manner
• Only neighbours are known

Example: Border gateway protocol (BGP) now maintains cost estimates

Question 3

What is meant by an area in an OSPF autonomous system?

Answer 3

System divides its hierarchy into an area consisting of routers that help in broadcasting the link state to the other routers in the same area.

Question 4

Why introduce the concept on an area?

Answer 4

The area will be responsible for routing traffic between other areas of the system.

Question 5

Uncontrolled flooding properties

Answer 5

• A node may receive multiple copies of the same packet
• A node may forward multiple copied of a packet over the same outgoing link

Question 6

Controlled Flooding properties

Answer 6

• A node may receive multiple copies of the same packet
  -A node MAY NOT forward multiple copies of a packet over the same outgoing link

Question 7

Spanning tree broadcast properties

Answer 7

• A node MAY NOT receive multiple copies of the same packet
• A node MAY NOT forward multiple copies of a packet over the same outgoing link