14.6. Network protocols
A subsection of Information Technology, 9626, through 14. Communications technology
Listing 10 of 32 questions
A packet switched network has routers at nodes labelled A, B, C, D, E, F, G and H. Each router stores its own ‘routing table’ which shows how it is connected to the other routers. Router Connected to routers: A B B A C D C B D E F D B C F E C F F C D E G G F H H G Complete the diagram by drawing routers C, D, E, F and G with connection lines to show how the routers are inter-connected to communicate with each other. A B H Router A regularly sends out packets to check that router H is reachable. When H receives a packet from A it sends a packet back to confirm that it is reachable. Assume that each router takes zero time units to receive, process and resend a packet and that each packet takes six time units to travel from one router to the next. Describe the shortest route that a packet can take from router A to router H. Calculate the shortest time taken for router A to receive an acknowledgement from router H confirming that H is reachable. Assuming that the packets visit each router only once, calculate the longest time it could take for router A to receive an acknowledgement from router H confirming that H is reachable. Describe the route that the packets would take. An additional router, J, is to be added to reduce the time for packets to travel from router A to router H to a minimum. However, no further connections can be directly made to routers A and H. Describe where J would be placed to reduce the travel time to a minimum. Calculate the new minimum time that it would take for A to receive an acknowledgement that H was reachable.
9626_s19_qp_32
THEORY
2019
Paper 3, Variant 2
View
Fig. 3 shows a diagram of interconnected computer networks that use internet protocol (IP) and packet switching to communicate. A large file is sent from network A to network H. Nodes B to G are routers used to connect the networks. During the sending of the file from network A, network I also starts to send a much larger video file to network H. A B G C E D F H I File sent from A File from A being received at H File from I being received at H File sent from I Fig. 3 Explain, in detail with reference to the diagram, how the file from network A and the file from network I travel through the network from router to router and start to arrive at network H at the same time. Explain why router C does not always send the packets to router D.
9626_w18_qp_32
THEORY
2018
Paper 3, Variant 2
View
Questions Discovered
32