lecture5PSI

Question 1

What is routing?

Answer 1

Routing = finding a path between a specific source and
destination station

Question 2

What is external routing?

Answer 2

Routing between networks of different ISPs. External routing protocols
(e.g. BGP, see later) are used for this routing

Question 3

What is a proactive routing and when it is used?

Answer 3

Proactive routing = maintain routing information up to date.
Proactive routing is used in networks that do not change or always change over a longer
period of time.

Question 4

What is an internal routing?

Answer 4

Routing within a network belonging to one ISP. Internal routing protocols
(e.g. OSPF, RIP) are used for this routing

Question 5

How does flood routing works and why do we use it?

Answer 5

Flood routing is performed in order to construct the spanning tree of the network graph, the spanning tree of the network graph is important because it allows data to be delivered acyclically from the root node to all other nodes

Question 6

What are the routing table entries?

Answer 6

Destination, Gateway, Mask, Metric, Interface

Question 7

Whan do we use redundant routing?

Answer 7

Redundant routing is commonly used when it is
necessary to guarantee high availability of the
destination station

Question 8

What is a redundant routing?

Answer 8

Redundant routing = routing to the destination
station is possible via multiple mutually disjoint
paths. The router chooses one path based on a
certain criterion (e.g. shortest distance)

Question 9

What is a path?

Answer 9

Path = the sequence of routers that a packet must pass between a
source and a destination station

Question 10

What are the static routing properties?

Answer 10

▶ It works immediately after turning the routers on.
▶ It is not able to respond to changes.
▶ Requires manual configuration of all elements → hard for large networks.
▶ It is mainly suitable for smaller networks with a simple structure

Question 11

What algorithms does DVA use and in which routing protocol it is used?

Answer 11

It uses Distributed version of the Bellman-Ford Algorithm (DBFA), it is used in a routing protocol called RIP = Routing Information Protocol

Question 12

What is ISP?

Answer 12

ISP = Internet Service Provider, connection provider with assigned specific IP ranges

Question 13

What types of routing do you know?

Answer 13

1. Optimal
2. Redundant
3. By symmetry
   3.1 Symmetrical
   3.2 Asymmetric
4. According to the way-finding method
   4.1 Flood
   4.2 Proactive
   4.3 Reactive
5. According to the calculation area
   5.1 Internal
   5.2 External

Question 14

What is an autonomous system?

Answer 14

Group of all IP address ranges of a specific ISP. Each AS has
its own specific identifier. Identifiers are used for external routing

Question 15

Tell me about EIGRP (Enhanced Interior Gateway Routing Protocol)

Answer 15

It is an advanced distance-vector routing protocol, that was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers, unlike RIP, EIGRP only sends incremental updates, reducing the workload on the router
and the amount of data that needs to be transmitted

Question 16

What is reactive routing and when it is used?

Answer 16

Reactive routing = find a route when needed. The use of this type of routing makes sense, for example, in mobile networks or in ad-hoc
networks, because their arrangement (topology) changes frequently

Question 17

What algorithms does DVA use and in which routing protocol it is used?

Answer 17

LSA uses Dijkstra’s algorithm, and is is being used in OSPF or IS-IS

Question 18

What is PVA? How it works?

Answer 18

It is Path Vector Algorithms (PVA) a dynamic routing algorithm. A typical representative of dynamic routing protocols using PVA is BGP = Border
Gateway Protocol.

Question 19

3 dynamic routing algorithms

Answer 19

▶ Distance Vector Algorithms (DVA)
▶ Link State Algorithms (LSA)
▶ Path Vector Algorithms (PVA)