University of Southern California EE450 Introduction to Computer Networks Final Exam 2 10 Hours May 7 2021 Last Name First Name Part 1 T F Part 2 MC Part 3 Fill in the Blank Part 4 Routing Algorithms Part 5 TCP Congestion Control X Credit Addressing Subnetting Total 20 10 30 20 20 10 110 Notes The exam is 2hours and 10 minutes plus an extra 30 minutes to be used for organizing to write your name and number your pages scanning printing and uploading ONLY The drop box will close at 10 40 PM I will NOT accept any exam via e mail One File and one upload ONLY make sure You can work the problems in any order you wish including the x credit the goal is to try to accumulate as many points as you can Try your best to be clean and to show all the steps of your work Anything I can NOT read I will NOT grade Rules This is a closed book closed notes exam One 8 x11 containing formulas only is allowed along with a calculator It is preferred if you use a dark pen rather than a pencil Adherence to the University s Code of Ethics will be strictly monitored and enforced Academic Integrity violations such as cheating will result in a series of actions and penalties including the student failing the class EE450 Spring 2021 Final Zahid 1 F T F F T Part 1 True False 1 Subnetting is the process of extracting the network address from an IP address 2 TCP has the property of slow start to probe the congestion level in the network 3 The MTU is the maximum number of Bytes that the IP packet can encapsulate 4 Communications can be initiated either from the private network or from the public network if the private network is using a NAT mechanism 5 The following masks in slash notation for simplicity are only used as default masks 8 16 and 24 6 In link state routing every router has the same link state database but the routing tables are different in each router 7 In distance vector routing each router receives distance vectors from every router in the network 8 Unlike Ethernet wireless nodes may not be able to transmit and listen at the same IF time making collision detection impossible 9 In TCP A source s retransmission timeout value RTO is always set equal to the te most recently measured RTT 10 An ACK number of 500 in the TCP header indicates that the receiver has received 499 Bytes and the next byte it expects to receive is 500 11 The outcome of the routing process is used to populate the forwarding tables at the z routers 12 If an IP fragment does not arrive at the destination then only that fragment not the entire packet is retransmitted by the source host 13 The IP header changes each time a packet passes through an IP router T TL 14 Unlike in shared hubs unicast frames are never flooded in switched Ethernet TO F T EE450 Spring 2021 Final Zahid 2 TF TE F T T 15 In 802 3 standard if the maximum size coverage were increased the minimum znrhi frame size would increase as well 16 In 802 3 standard if the bandwidth isincreased the minimum frame size would not pop t ti v v 17 In 802 3 if an ACK is not received within a specified time timeout the sender will 18 In the case fragmentation is needed the TCP UDP headers always end up in the first increase as well retransmit the frame fragment 19 If a TCP and a UDP flows share the same bottleneck the UDP flow is more likely will get a greater percentage of the bandwidth 20 In An Ethernet Adapter passes only non corrupt frames that it receives up to the O o network layer EE450 Spring 2021 Final Zahid 3 Part 2 Multiple Choice Questions d 1 Suppose a Certificate Authority CA has Bob s certificate registered with it binding Bob s public key to Bob This certificate is signed with 2 A sender sends an unencrypted message and its encrypted digest over a network Which of the following types of information assurance is provided in this scenario b 3 A sender sends a message encrypted by a public key of the recipient Which of the following is NOT provided in this scenario a Bob s public key b The CA s public key c Bob s private key d The CA s private key a Authentication b Integrity c Confidentiality d None of the above a Confidentiality b Integrity c Authentication d All the above a Integrity b Confidentiality c Authentication d All the above 4 A sender sends a message encrypted by his own private key Which of the following has is NOT provided in this scenario Tied EE450 Spring 2021 Final Zahid 4 ae Hub 5 Replacing a Hub by a switch results in Circle all that applies Swbffnh si a It increases the number of collision domains b It decreases the number of collision domains c It increases the number of broadcast domains d It decreases the number of broadcast domains e It makes smaller collision domains f It makes larger collision domains 6 Based on the following diagram choose all that applies to device A circle all that bde applies a With a network wide mask of 255 255 255 128 each interface does not require an b With a network wide mask of 255 255 255 128 each interface does require an IP c With a network wide mask of 255 255 255 0 it must be a Layer 2 device for the d With a network wide mask of 255 255 255 0 it must be a Layer 3 device for the PCs to communicate with each other PCs to communicate with each other e With a network wide mask of 255 255 254 0 each interface does not require an IP IP address i address EE450 Spring 2021 Final Zahid 5 7 In the following diagram which destination addresses will be used by Host A to send data to Host C circle all that apply Cf resided a The IP address of Switch 1 b The MAC address of Switch 1 c The IP address of Host C d The MAC address of Host C e The IP address of the router s E0 interface f The MAC address of the router s E0 interface 8 Which statement describes remote access VPNs Select all that applies a a Client software is usually required to be able to access the network b Remote access VPNs are used to connect entire networks such as a branch office airs to headquarters c Remote access VPNs support the needs of telecommuters and mobile users d A dedicated line is required to implement remote access VPNs e End users are not aware that VPNs exists In EE450 Spring 2021 Final Zahid 6 9 Based on the VLSM addressing scheme what prefix will RA advertise to the co Internet a 172 16 0 …