Question 1 Routing (10 marks)

Given the following network diagram, assume that all the networks shown are aware of each other and have fully updated routing tables. Answer the questions that follow.

The questions (1 mark each except q.8):

From the point of view of router R4, what is the next-hop address for a packet addressed to host 161.22.0.15/18?

From the point of view of router R1, which of its interfaces would it choose for a packet being sent to network 161.22.0.0/18?

A host with an IP address of 200.11.60.36/24 has just sent a packet to a host with address 150.32.0.240/18. How many hops is required between source and destination?

A packet originating from network 220.10.40.0/24 arrives at router R1, however, R1 determines that the destination network is not in its routing table. What does R1 do with the packet?

A packet arrives at router R2 with a destination address of 140.21.0.10/22. Which interface port does R2 forward the packet out of?

A packet at router R3 has a destination address of 220.10.40.5/24. What next-hop address would R3 use for this packet?

A packet is waiting at router R4 for forwarding. If the next-hop was a direct delivery, which of these three networks is the destination network? 150.3.0.0/16, or 150.32.0.0/18, or 220.10.40.0/24?

Complete the information in the routing table for router R2 as shown in the Answer Template for networks 150.3.0.0/16, 150.32.0.0/18, and the Default network. Show the masks in longest mask order using CIDR format (3 marks).

Question 2 Fragmentation in IPv4 (5 marks)

An IP datagram 5,400 bytes long with no options arrives at a router, which determines that the next destination has an MTU of 1,500 bytes. Use the Answer Template to complete the following questions, showing your calculations and reasoning.

Assuming that the router decides to fragment the packet into 4 fragments, determine a correct size for each fragment, and identify the starting byte and ending byte of each fragment (2.5 marks).

Calculate the fragmentation offset for each fragment (1.5 marks).

State whether the total number of bytes from all 4 fragments leaving the router will be greater than the initial datagram size that arrived, or less than the initial datagram size, and the reason (1 mark).

Question 3 Congestion controls in TCP (10 marks)

This question affords you the opportunity to extend your thinking about congestion controls in TCP beyond the textbook to observe what a real-world technology company, Google, is doing in this space.

First, read this Network World article that reports on Googles approach to improving congestion controls in TCP:

https://www.networkworld.com/article/3218084/lan-wan/how-google-is-speeding-up-the-internet.html?idg_eid=f32fc7aec843db7ef67d0a4f08e3322d&email_SHA1_lc=&cid=nww_nlt_networkworld_daily_news_alert_2017-08-22&utm_source=Sailthru&utm_medium=email&utm_campaign=NWW%20Daily%20AM%20Alert%202017-08-22&utm_term=networkworld_daily_news_alert

You should also read the following more technical paper about it: https://tools.ietf.org/id/draft-cardwell-iccrg-bbr-congestion-control-00.html

After reading both articles, answer the following questions:

Write a brief summary of the congestion controls currently available in TCP as covered in this Unit (1 mark)

Identify and explain two problems with current congestion controls in TCP that are pointed out in the articles (2 marks)

Summarize in your own words the difference(s) between the current TCP congestion controls and Googles new BBR protocol (3 marks)