This set of Computer Networks Multiple Choice Questions & Answers (MCQs) focuses on “Hierarchical Routing”.
1. Which of the following routing saves more memory in case of storing information about routers in the network?
a) Link state routing
b) Hierarchical routing
c) Broadcast routing
d) Distance vector routing
View Answer
Explanation: Unlike other routing tables, the routing tables in hierarchical routing will have entries for their neighbour within the region and entry for each region in the network. Also, this levelling in storing entries, saves the memory of the router in case of large network.
2. Which name is used for the parts in the network that are divided by hierarchical routing in two level hierarchy?
a) Groups
b) Zones
c) Regions
d) Clusters
View Answer
Explanation: Regions are small parts of the network with dedicated number of routers and these regions can be grouped to form clusters. Clusters can be grouped to form zones, zones into groups. A network can be levelled with names until we run short of names.
3. What is the number of entries in a router, if it belongs to a region with 11 routers and the network has 5 regions?
a) 11
b) 14
c) 15
d) 16
View Answer
Explanation: The routing table will have total number of 15 entries for 11 routers, which belongs to the same region. And 4 entries for the regions other than the one in which the router is present.
4. Routers in the hierarchical routing stores the information about every other router in the network?
a) False
b) True
View Answer
Explanation: Hierarchical routing is to divide the network into tiers that are regions, clusters, zones, groups and so on. Because of this hierarchy, the router need not to have entries for every router in the network. And, it is enough to have entries for routers from the same region and each entry for; clusters, zones, groups, depending on the level of hierarchy.
5. What is the optimum number of levels(hierarchical) that are required for a network if it has M number of routers?
a) Levels = ln M
b) Levels = M
c) Levels = M2
d) Levels = M/2
View Answer
Explanation: A network with “ln M” levels and “e ln M” entries for each router can be treated as optimum in levelling. This was discovered by Kamoun and Kleinrock in 1979.
6. How many entries will be in router4 in the given network if it uses hierarchical routing?
a) 3
b) 4
c) 2
d) 1
View Answer
Explanation: The above network is using hierarchical network. So, the router4 will have one entry for itself and two entries for the other two regions. It will have the entry for itself in its routing table even though it is the only router in the region.
7. A network with two level hierarchy has total of 1600 routers and got divided into some parts, a router in the first part which consists of 500 routers has 503 entries in it. The second part and third part have routers with 303 and 603 entries respectively. What is the total no of regions in the network and how many routers are present in each part?
a) 4; 500, 300, 600, 200
b) 5; 400, 500, 200, 100, 400
c) 3; 500, 600, 500
d) 4; 500, 300, 500, 300
View Answer
Explanation: Network has two level hierarchy and router in the first part has 3 extra entries more than the number of routers in that part. This indicates that the network has divided into 4 parts. After subtracting 500, 300 and 600 from 1600, we get 200 routers in the last part.
8. Which of the following is a disadvantage of the hierarchical routing?
a) It is simple
b) Non-optimal
c) Collision is avoided
d) Fair channel allocation
View Answer
Explanation: Hierarchical routing is simple but it is not optimum. In order to achieve optimum route, every router must be aware of all the routers in the network, it is not possible in hierarchical routing.
9. Which of the following statement is incorrect in case of hierarchical routing?
a) Simple
b) No collisions
c) Non-optimal
d) Reservation based scheduling
View Answer
Explanation: Hierarchical routing does not provide optimum paths for the packet transmission, because every router is not aware of the routes other that the core routers. And, each region may use different local routing algorithms which makes routing non-optimal.
10. Fair channel allocation is provided by the network in hierarchical routing.
a) True
b) False
View Answer
Explanation: A large network is divided into levels which facilitates the devices with good channel allocation. As the number of devices decreases for each part(region), the network communication will be easy in regions.
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