Routing

Question 1

How is global information classified in a routing algorithm?

Answer 1

All routers have complete topology alongside the link cost info.

There’s also the presence of link state algorithms.

Question 2

How is decentralized information classified in a routing algorithm?

Answer 2

The router knows physically connected neighbors and the link costs to those neighbors.

There is an iterative process of computation and the exchange of information with neighbors

There’s the presence of distance vector algorithms

Question 3

What are the characteristics of a static routing algorithm?

Answer 3

This is hardly an algorithm. The network administrator establishes table mappings. These mappings do not change unless network admin alters them.

Question 4

What are the characteristics of a dynamic routing algorithm?

Answer 4

Routes change more quickly due to periodic updates and also in response to link cost changes

Question 5

Describe flooding

Answer 5

Flooding is a static algorithm that sends out every incoming packet on every outgoing line except the one it arrived on. It generates vast numbers of duplicate packets, an infinite number unless measures are taken to dampen the process.

Question 6

What is a measure that can be used to reduce the number of duplicate packets during flooding?

Answer 6

A hop counter contained in the header of each packet and that is decremented at each hop. The packet is discarded when the counter reaches zero.

Question 7

Is flooding practical?

Answer 7

It isn’t practical in many applications because of the large number of packets generated.

Question 8

What are the applications of flooding?

Answer 8

Robust, for example military applications where large numbers of routers may be destroyed at any instance.

Broadcasting for example distributed database applications since you can update all of the databases concurrently.

It always chooses the shortest path since it chooses every possible path in parallel.

Question 9

What is an advantage of using flooding?

Answer 9

No other algorithm can produce a shorter path

Question 10

How do routing algorithms view the network?

Answer 10

The view them as a graph

Question 11

What are the factors that affect routing?

Answer 11

Semi-dynamic topology (deal with link failures)
Dynamic load: congestion/delay
Policy

Question 12

What is the internet?

Answer 12

A collection of Autonomous Systems. It is defined by control not geography

Question 13

What are the two types of routing?

Answer 13

Intra Domain Routing
Inter Domain Routing

Question 14

What are examples of intra domain routing?

Answer 14

Distance vector
Link State

Question 15

What are examples of inter domain routing?

Answer 15

Path vector

Question 16

What are characteristics of dynamic routing algorithms?

Answer 16

In the environment the links and routers are unreliable, and the traffic patterns can change rapidly.

The algorithms used are the distance vector algorithm and the link state algorithm both of these assume the router knows the address of each neighbor and cost of reaching each neighbor. The router gets to determine the global routing information by talking to its neighbors.

Question 17

What is the basic idea of the distance vector?

Answer 17

The node tells it neighbors its best idea of distance to every other node in the network. The node then receives these distance vectors and updates its notion of best path to each destination and the next hop for this destination.

It is distributed and adapts to traffic changes and link failures

Question 18

Why does the distance vector work?

Answer 18

Each node knows its true cost to its neighbors. This information is spread to its neighbors the first time it sends out its distance vector.
Each dissemination spreads the truth one hop and eventually it is incorporated into routing table everywhere in the network.

Question 19

What is the basic idea of the link state?

Answer 19

Each router must discover its neighbors and learn their network addresses.
Measure the delay or cost to each of its neighbors
Construct a packet telling all it has learned
Flood the router using link state packets
Compute the shortest path to every other router

Question 20

How is information distributed for the map?

Answer 20

Each node periodically makes up a short message, the link state packets. These identify the node which is producing it and identifies all the other nodes to which it is directly connected. Includes a sequence number which increases every time the source node makes up a new version of the message.

Question 21

What is the difference between distance vector routing protocols and link state routing protocols?

Answer 21

Distance vector are simple and efficient in small networks and require little if any management and do not scale well and have poor convergence. On the other hand link state routing protocols require more processing power and more memory, use flooding and are more scalable than simple distance vector protocols for use in large networks.

Question 22

What are examples of distance vector and link state protocols used in intra domain routing protocols?

Answer 22

Distance Vector - Routing Information Protocol (RIP)

Link State - Open Shortest Path First (OSPF)

Question 23

What are characteristics of Routing Information Protocol?

Answer 23

It is a distance vector routing protocol. The cost metric is hop count and its is useful for small subnets since it is easy to install.

Question 24

What are characteristics of Routing Information Protocol?

Answer 24

It is a link state routing protocol. It is more scalable and complex than RIP

Question 25

Characteristics of intra domain routing vs inter domain routing

Answer 25

Distance vector and link state are examples of intradomain and these can be used inside an autonomous system but not between autonomous systems. These two protocols are not suitable for interdomain routing mostly because of scalability. This made the need for another routing protocol called path vector routing.

Question 26

What are characteristics of inter domain routing?

Answer 26

It uses a class of distance vector protocols called path vector routing.

Question 27

What is the principle of path vector routing?

Answer 27

The speaker node acts on behalf of the entire autonomous system. It creates a routing table of the nodes in its system and advertises this table to speaker nodes in the neighboring autonomous systems. The speaker node advertises the path of the nodes in its autonomous system.

Question 28

What is an explanation of the border gateway protocol (BGP)?

Answer 28

It uses path vector routing where the distance vector is annotated with the entire path and with the policy attributes. It is guaranteed loop free

Question 29

What are the uses of multicast?

Answer 29

Any applications with multiple receivers
Live Video Distribution
Collaborative Groupware
e-Learning
Periodic Data Delivery - “Push” technology such as stock quotes
Server/Web-site replication
Reducing Network/Resource Overhead - this is more efficient to multicast rather than multiple unicasts

Question 29

What is Internet Group Management Protocol (IGMP)?

Answer 29

This is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships.

Question 30

What can IGMP be used for?

Answer 30

One to many networking applications such as online streaming and gaming since it allows for more efficient use of resources when supporting these types of applications.

Question 31

What network is IGMP used on?

Answer 31

Ipv4 networks

Question 32

What is Multicast Listener Discovery used for?

Answer 32

It is used for multicast management on IPv6 networks

Question 33

What is hierarchical routing used for?

Answer 33

It is used to solve the problem of large networks needing large routing tables to have more computation to find shortest paths and more bandwidth