Network Layer

Question 81

Match the following:

• (1)

• (2)

• (3)

• (4)

Question 82

Assume that source S and destination D are connected through two intermediate routers labeled R. Determine how many times each packet has to visit the network layer and the data link layer during a transmission from S to D.

• Network layer – 4 times and Data link layer – 4 times
• Network layer – 4 times and Data link layer – 3 times
• Network layer – 4 times and Data link layer – 6 times
• Network layer – 2 times and Data link layer – 6 times

Question 83

Consider a source computer(S) transmitting a file of size 10⁶ bits to a destination computer(D)over a network of two routers (R₁ and R₂) and three links(L₁, L₂, and L₃). L₁connects S to R₁; L₂ connects R₁ to R₂; and L₃ connects R₂ to D.Let each link be of length 100 km. Assume signals travel over each link at a speed of 10⁸ meters per second.Assume that the link bandwidth on each link is 1Mbps. Let the file be broken down into 1000 packets each of size 1000 bits. Find the total sum of transmission and propagation delays in transmitting the file from S to D?

• 1005 ms
• 1010 ms
• 3000 ms
• 3003 ms

Question 84

Consider a network with five nodes, N1 to N5, as shown below. The network uses a Distance Vector Routing protocol. Once the routes have stabilized, the distance vectors at different nodes are as following. N1: (0, 1, 7, 8, 4) N2: (1, 0, 6, 7, 3) N3: (7, 6, 0, 2, 6) N4: (8, 7, 2, 0, 4) N5: (4, 3, 6, 4, 0) Each distance vector is the distance of the best known path at the instance to nodes, N1 to N5, where the distance to itself is 0. Also, all links are symmetric and the cost is identical in both directions. In each round, all nodes exchange their distance vectors with their respective neighbors. Then all nodes update their distance vectors. In between two rounds, any change in cost of a link will cause the two incident nodes to change only that entry in their distance vectors. 52. The cost of link N2-N3 reduces to 2(in both directions). After the next round of updates, what will be the new distance vector at node, N3.

• (3, 2, 0, 2, 5)
• (3, 2, 0, 2, 6)
• (7, 2, 0, 2, 5)
• (7, 2, 0, 2, 6)

Question 85

Consider the data given in above question. Suppose the weights of all unused links in the previous question are changed to 2 and the distance vector algorithm is used again until all routing tables stabilize. How many links will now remain unused?

• 0
• 1
• 2
• 3

Question 86

Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries:

Prefix           Output Interface Identifier
131.16.0.0/12              3
131.28.0.0/14              5
131.19.0.0/16              2
131.22.0.0/15              1

The identifier of the output interface on which this packet will be forwarded is ______.

• 1
• 2
• 3
• 5

Question 87

Two computers C1 and C2 are configured as follows. C1 has IP address 203.197.2.53 and netmask 255.255.128.0. C2 has IP address 203.197.75.201 and netmask 255.255.192.0. which one of the following statements is true?

• C1 and C2 both assume they are on the same network
• C2 assumes C1 is on same network, but C1 assumes C2 is on a different network
• C1 assumes C2 is on same network, but C2 assumes C1 is on a different network
• C1 and C2 both assume they are on different networks.

Question 88

Assume the following information: Original timestamp value = 46 Receive timestamp value = 59 Transmit timestamp value = 60 Timestamp at arrival of packet = 69 Which of the following statements is correct?

• Receive clock should go back by 3 milliseconds
• Transmit and Receive clocks are synchronized
• Transmit clock should go back by 3 milliseconds
• Receive clock should go ahead by 1 milliseconds