(a). Suppose each node creates a report from its initial configuration and sends
ID: 3589157 • Letter: #
Question
(a). Suppose each node creates a report from its initial configuration and sends that to each of its neighbors. What will each node’s forwarding table be after this set of exchanges? The exchanges, in other words, are all conducted simultaneously; each node first sends out its own report and then processes the reports arriving from its two neighbors.
(b). What will each node’s table be after the simultaneous-and-parallel exchange process of part (a) is repeated a second time?
Hint: you do not have to go through each exchange in detail; the only information added by an exchange is additional reachability information.
Explanation / Answer
(a) Answer:
For Node A:
It has <B,B,1> and <D,D,1>
Node B will send <A,A,1> , <C,C,1>
Node D will send <A,A,1> , <E,E,1>
As Node A came to know it can reach C through B at cost of 2 (A to B 1+from B to C 1), E through D at cost of 2 (A to D 1+from D to E 1),
A will update its table as <B,B,1> , <C,B,2> , <D,D,1> , <E,D,2>
For Node B:
It has <A,A,1> and <C,C,1>
Node A will send <B,B,1> , <D,D,1>
Node C will send <B,B,1> , <F,F,1>
As Node B came to know it can reach D through A at cost of 2 (B to A 1+from A to D 1), F through C at cost of 2 (B to C 1+from C to F 1),
B will update its table as <A,A,1> , <C,C,1> , <D,A,2> , <F,C,2>
For Node C:
It has <B,B,1> and <F,F,1>
Node B will send <A,A,1> , <C,C,1>
Node F will send <C,C,1> , <E,E,1>
As Node C came to know it can reach A through B at cost of 2 (C to B 1+from B to A 1), E through F at cost of 2 (C to F 1+from F to E 1),
C will update its table as <A,B,2> , <B,B,1> , <E,F,2> , <F,F,1>
For Node D:
It has <A,A,1> and <E,E,1>
Node A will send <B,B,1> , <D,D,1>
Node E will send <D,D,1> , <F,F,1>
As Node D came to know it can reach B through A at cost of 2 (D to A 1+from A to B 1), F through E at cost of 2 (D to E 1+from E to F 1),
D will update its table as <A,A,1> , <B,A,2> , <E,E,1> , <F,E,2>
For Node E:
It has <D,D,1> and <F,F,1>
Node D will send <A,A,1> , <E,E,1>
Node F will send <C,C,1> , <E,E,1>
As Node E came to know it can reach A through D at cost of 2 (E to D 1+from D to A 1), C through F at cost of 2 (E to F 1+from F to C 1),
E will update its table as <A,D,2> , <C,F,2> , <D,D,1> , <F,F,1>
For Node F:
It has <C,C,1> and <E,E,1>
Node C will send <B,B,1> , <F,F,1>
Node E will send <D,D,1> , <F,F,1>
As Node F came to know it can reach B through C at cost of 2 (F to C 1+from C to B 1), D through E at cost of 2 (F to E 1+from E to D 1),
F will update its table as <B,C,2> , <C,C,1> , <D,E,2> , <E,E,1>
(b) Answer:
In second iteration
For Node A:
It has <B,B,1> , <C,B,2> , <D,D,1> , <E,D,2>
Node B will send <A,A,1> , <C,C,1> , <D,A,2> , <F,C,2>
Node D will send <A,A,1> , <B,A,2> , <E,E,1> , <F,E,2>
As Node A came to know it can reach F through B at cost of 3 (A to B 1+from B to F 2) or through D at same cost.
A will update its table as <B,B,1> , <C,B,2> , <D,D,1> , <E,D,2> , <F,B,3>
For Node B:
It has <A,A,1> , <C,C,1> , <D,A,2> , <F,C,2>
Node A will send <B,B,1> , <C,B,2> , <D,D,1> , <E,D,2>
Node C will send <A,B,2> , <B,B,1> , <E,F,2> , <F,F,1>
As Node B came to know it can reach E through A at cost of 3 (B to A 1+from A to E 2) or through C at same cost.
B will update its table as <A,A,1> , <C,C,1> , <D,A,2> , <E,A,3> , <F,C,2>
For Node C:
It has <A,B,2> , <B,B,1> , <E,F,2> , <F,F,1>
Node B will send <A,A,1> , <C,C,1> , <D,A,2> , <F,C,2>
Node F will send <B,C,2> , <C,C,1> , <D,E,2> , <E,E,1>
As Node C came to know it can reach D through B at cost of 3 (C to B 1+from B to D 2) or through F at same cost.
C will update its table as <A,B,2> , <B,B,1> , <D,B,3> , <E,F,2> , <F,F,1>
For Node D:
It has <A,A,1> , <B,A,2> , <E,E,1> , <F,E,2>
Node A will send <B,B,1> , <C,B,2> , <D,D,1> , <E,D,2>
Node E will send <A,D,2> , <C,F,2> , <D,D,1> , <F,F,1>
As Node D came to know it can reach C through A at cost of 3 (D to A 1+from A to C 2) or through E at same cost.
D will update its table as <A,A,1> , <B,A,2> , <C,A,3> , <E,E,1> , <F,E,2>
For Node E:
It has <A,D,2> , <C,F,2> , <D,D,1> , <F,F,1>
Node D will send <A,A,1> , <B,A,2> , <E,E,1> , <F,E,2>
Node F will send <B,C,2> , <C,C,1> , <D,E,2> , <E,E,1>
As Node E came to know it can reach B through D at cost of 3 (E to D 1+from D to B 2) or through F at same cost.
E will update its table as <A,D,2> , <B,D,3> , <C,F,2> , <D,D,1> , <F,F,1>
For Node F:
It has <B,C,2> , <C,C,1> , <D,E,2> , <E,E,1>
Node C will send <A,B,2> , <B,B,1> , <E,F,2> , <F,F,1>
Node E will send <A,D,2> , <C,F,2> , <D,D,1> , <F,F,1>
As Node F came to know it can reach A through C at cost of 3 (F to C 1+from C to A 2) or through E at same cost.
F will update its table as <A,C,3> , <B,C,2> , <C,C,1> , <D,E,2> , <E,E,1>
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