Internet-routing

Question 1

Say at least 2 requirements for good routing.

Answer 1

For example:
* Efficient
* Simple
* Robust
* Optimal
* Stable
Aka: good.

Question 2

How is routing for a virtual circuit different than for packet circuit?

Answer 2

A virtual circuit only routes when establishing the connection.
A packet switching circuit routes each packet individually. (potentially different paths)

Question 3

What does the least-cost routing criteria mean?

Answer 3

You give each route a cost based on a criteria and pick the cheapest total route.

Question 4

What does the minimum-hop route mean?

Answer 4

The route with the lowest number of hops needed is picked. Probably not the best route all the time.

Question 5

A routing decision can take place on two different places, what are the two types of routing?

Upsides/downsides?

Answer 5

• Centralized: Decision is made by a designated node. This is vulnerable to attacks.
  *Distributed: Every node routes the output it recieves. This is more complex but also more robust.

Question 6

Can you name some routing strategies?

Answer 6

-Fixed routing
-Flooding
-Adaptive routing

Question 7

What are the down/upsides of fixed routing?

(what is fixed routing?)

Answer 7

Fixed routing means you have one “fixed” route between each pair of nodes.
* Upsides: Simple, works well on networks with reliable load.
* Downside: Is not flexible and does not react to failures.

Question 8

What are the up/downsides of flooding as a routing strategy?

Answer 8

Flooding means you send the packet to all other neighbors who did not send the packet. “Flooding the network with the packet”.
* Upside: All possible routes are tested which makes failure near impossible. The packet arriving first will have used the shortest path.
* Downside: High traffic load and security concerns as you need a system to avoid loops in the network.

Question 9

What are the upsides or downsides to adaptive routing?

Answer 9

As the name suggests, adaptive routing has the ability to adapt by re-routing if needed. This is either due to failure in the nodes/paths or congestion caused by high traffic loads in a specific part of the network.
* Upsides: This has high performance and decreases the risk of congestion.
* Downsides: This is a complex system which requires processing power. Additionally the info you need to periodically exchange between the nodes degrades performance. Finally, fluctuations in traffic load can still cause poor performance.

Question 10

Are adapive schemes more commonly using local info for the node or info from all nodes to make decisions?

Answer 10

Strategies based on only local info are exceedingly rare. The scheme can however be both distributed or centralized. (nodes think for themselves or are told what to do).

Question 11

What are the two important terms used for describing first and second generation routing?

Answer 11

The terms are distance-vector routing.
(1st gen routing using estimated delay as performace criterium with Bellman-Ford algorithm.)

-and Link-State routing.
(2nd gen routing using measured delay as performance criturium with Djikstra’s algorithm.)
adaptive