1. Delay Tolerant Networks Routing Protocols                             [33 marks]

a) Which protocol would have a better performance in a Smart City pedestrian scenario, Spray and Wait or Spray and Focus? Please explain why. [5 marks]

b) Provide brief description of the functionality of “contact manager” and “congestion manager” in the Café routing protocol. Explain why both functionalities are needed. [5 marks]

c) What problem with congestion is not solved by the Autonomous Congestion Control protocol (ACC)? Please provide an example of a DTN protocol that solves it. [5 marks]

d) Describe the fully autonomous decision making in open-loop DTN protocols. How can it improve the problem of faults in smart manufacturing environments with multiple robots, assembly lines and Industrial Internet of Things (IIoT)? [5 marks]

e) Explain three different challenges for the use of aerial vehicles (UAV) and ground vehicles (UGV) network communications in smart cities for emergency applications. [3 marks]

f) Consider a busy underground with no mobile coverage/no cellular network/no WiFi. Which type of network and protocol would you use to report an accident? Justify your answer. [3 marks]

g) Read through the pseudo-code below and identify which DTN algorithm it implements. Justify your answer. [7 marks]

upon reception of Hello message h from node m do

if newNeighbour(m) == true

if msgQueue.hasMsgsForDest(m) == true

deliverMsgs(m)

requestEncounters(m)

upon reception of encounter vector ev from node m do

addNodeEncounters(m, ev)

updateBetweenness()

updateSimilarity()

exchangeSummaryVector(m)

upon reception of summary vector sv from node m do

Vector requestMsgs

for all destinations e   sv do

if m.utility(d) < utility(d)

requestMsgs.add(d)

sendMsgRequest(m, requestMsgs)

upon reception of message request vector mrv from node m do

Vector transferMsgs

for all messages e  mrv do

transferMsgs.add(msgQueue.getMsgs(d))

sendTransferMsgs(m, transferMsgs)

upon reception of transfer message tm from node m do

msgQueue.add(tm)

2. Mobile Ad Hoc Networks and Vehicular Ad Hoc Networks        [33 marks]

a) What are the two connectivity aspects of VANETs that differentiate them from MANETs? Please provide an example of a protocol which can be used with VANETs and justify your answer. [5 marks]

b) Describe and compare Beacon and Event safety messages in VANETs. Which of these two types of safety messages will be used to report on an accident? [5 marks]

c) Explain how you would need to change traditional VANET protocols to enable disconnection and disruption tolerance. [5 marks] 

d) Explain one way how you could change a passive MANET protocol to enable improved energy efficiency. [5 marks]

e) Provide three examples of information which cars send to infrastructure nodes and discuss the scenarios. [3 marks]

f) Is V2V communication in VANET sufficient for dealing with road accident reporting? Please justify your answer. [5 marks]

g) Consider a self-driving top instrumented car which has many sensors to allow the car to “see” exactly what a human driver would see. Would such a car need V2V communications? Explain your answer. [5 marks]

3. Delay Tolerant Networks Reliability                                          [33 marks]

a) What is more disruptive to a DTN, a black hole node or a grey hole node? Please discuss your answer. [6 marks]

b) Discuss how self-organised distributed reputation mechanisms can help malicious behaviour detection and prevention in DTNs. [7 marks]

c) List and discuss four features of IPNs that motivate the use of delay-tolerant communications? [4 marks]

d) Assume that there are 100 sensing edges monitoring temperature on the manufacturing floor. 99 of them are reporting 30 degrees and one is reporting 10 degrees. Does this mean that the single sensing edge reporting 10 degrees is faulty? Discuss your answer. [3 marks]

e) Describe how predicting “fault likelihood” can be done to help improve the reliability of DTNs and provide 5 examples of fault metrics which can be used for fault-aware communications. [7 marks]

f) Below is the First Contact router code as it appears in the ONE simulator. Modify it so   that it acts as a more disruptive Black Hole Router. Explain and justify your modifications. [6 marks]

package routing;

import core.Connection;

import core.DTNHost;

import core.Message;

import core.Settings;

/**

* First contact router which uses only a single copy of the message

* (or fragments) and forwards it to the first available contact.

*/

public class FirstContactRouter extends ActiveRouter {

public FirstContactRouter(Settings s) {

super(s);

}

protected FirstContactRouter(FirstContactRouter r) {

super(r);

}

@Override

protected int checkReceiving(Message m, DTNHost from) {

int recvCheck = super.checkReceiving(m, from);

if (recvCheck == RCV_OK) {

/* don't accept a message that has already traversed us */

if (m.getHops().contains(getHost())) {

recvCheck = DENIED_OLD;

}

}

return recvCheck;

}

@Override

public void update() {

super.update();

if (isTransferring() || !canStartTransfer()) {

return;

}

if (exchangeDeliverableMessages() != null) {

return;

}

tryAllMessagesToAllConnections();

}

@Override

protected void transferDone(Connection con) {

/* don't leave a copy for the sender */

this.deleteMessage(con.getMessage().getId(), false);

}

@Override

public FirstContactRouter replicate() {

return new FirstContactRouter(this);

}

}

4. Complex Network Topologies                        [33 marks]

a) Density aware Spray and Wait is an improvement of Spray and Wait. What is the key challenge of the Density Aware Spray and Wait protocol? Discuss two reasons it can fail. [5 marks]

b) Describe two differences between geographical routing and DTN routing protocols. Give examples of two application domains where you would use two different types of routing protocols. Justify your answers. [5 marks]

c) Describe the difference between a temporal network and a geo-temporal network. Please provide examples for each type of network. [5 marks]

d) Below is an extract of DTN connectivity events that is listed using the ONE connectivity format.

The ONE simulator reads DTN connectivity events using the connectivity format below.

T1 CONN n1 n2 up

T2 CONN n1 n2 down

The format is to be interpreted as follows:

At time T1 node n1 and node n2 come into contact with one another.

At time T2 node n1 and node n2 lose contact with one another other.

The nodes maintain contact between times T1 and T2.

Look at the DTN connectivity events provided below:

1 CONN 1 2 up

2 CONN 1 4 up

3 CONN 2 3 up

3 CONN 3 4 up

7 CONN 5 7 up

10 CONN 1 2 down

11 CONN 1 4 down

13 CONN 6 8 up

13 CONN 1 4 down

14 CONN 8 10 up

15 CONN 7 11 up

16 CONN 5 7 down

18 CONN 6 8 down

22 CONN 1 5 up

22 CONN 1 6 up

26 CONN 1 6 down

29 CONN 1 5 down

30 CONN 9 10 up

33 CONN 5 6 up

36 CONN 5 6 down

38 CONN 5 7 up

40 CONN 6 8 up

At time 4 node 2 generates a message M1 for node 10 and node 4 generates a message M2 for node 11.

i) Assuming that all nodes are using the First Contact protocol, determine if and when M1 and M2 will be delivered to their destination. Justify your answer. [4 marks]

ii) Assuming that all nodes are using Spray and Focus (with number of copies 3) protocol, determine if and when M1 and M2 will be delivered to its destination. Justify your answer. [4 marks]

iii) Which node has the highest degree connectivity? Justify your answer. [3 marks]

iv) Which nodes has the longest and the shortest connectivity durations? Justify your answer. [4 marks]

v) At time 20 which two nodes have the highest contact similarity? [3 marks]

5. Domain Name Service, Border Gateway Protocol, Information Centric Networks, and Content Centric Networks        [33 points]

a) With the aid of a diagram explain how information retrieval in web systems differs from information retrieval in mobile DTNs. [5 marks]

b) Describe two caching approaches in ICNs and explain the reasons for using them. [6 marks]

c) Describe two challenges of mobile publishers and two challenges of mobile subscribers. [4 marks]

d) Explain how you would modify data dissemination architecture so that a user can obtain trustable data from any untrusted node and over any untrusted link. [6 marks]

e) Describe and compare DNS and BGP architectures. [4 marks]

f) Describe and compare how the DNS and BGP would deal with records hijacking or misconfiguration of regional records? [4 marks]

g) Describe compare how DNS and BGP would deal with node failure [4 marks]