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3 votes
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In hierarchical routing with 4800 routers, what region and cluster sizes should be chosen to minimize the size of the routing table for the three-layer hierarchy?

  1. 10 clusters, 24 regions and 20 routers
  2. 12 clusters, 20 regions and 20 routers
  3. 16 clusters, 12 regions and 25 routers
  4. 15 clusters, 16 regions and 20 routers
in Others 5.7k views
1
I see the same question without options being asked. Is there a way to solve it directly , ans being 51. cube(17)=4913 but we have 4800 routers only. So how the ans is 51 , didn't understand that  part

1 Answer

4 votes
 
Best answer
$Clusters \times  regions \times routers =4800 \text{ for all options}$

 so we use following

$(clusters- 1) + (regions - 1) + routers$ , which option gives minimum is the ans...

 Option 1 gives us 52.

Option 2 gives us 50

Option 3 gives us 51

Option 4 gives us 49

So the answer is D

edited by
0
How the following formula came?

(clusters- 1) + (regions - 1) + routers , which option gives minimum is the ans...
2

that's how 

(clusters- 1) + (regions - 1) + routers 

 

0
Could you please explain further?
Answer:

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