Computer Networking Final Exam ALL QUIZ/MIDTERM QUESTIONS WITH CORRECT VERIFIED ANSWERS GUARANTEED PASS.

T/F: Before sending a packet into the internet, the source must determine all of the links that packet will traverse between source and destination. - correct answer False T/F: Layers four and five of the Internet protocol stack are implemented in the end systems but not in the routers in the network core. - correct answer True, Layers 4 and 5 are the Application and Transport layers T/F: The Internet provides its applications two types of services, a TDM (Time Division Multiplexing) service and a FDM (Frequency Division Multiplexing) service. - correct answer FALSE. Packet Switching is the now modern used service. T/F: Suppose 10 connections traverse the same link of rate 1 Gbps. Suppose that the client access links all have rate 5 Mbps. Then the maximum throughput for each connection is 100 Mbps. - correct answer False! Maximum throughput is limited to the smallest pipe, i.e. 5 Mbps. T/F: Consider a queue preceding a transmission link of rate R. Suppose a packet arrives to the queue periodically every 1/a seconds. Also suppose all packets are of length L. Then the queuing delay is small and bounded as long as aL < R. - correct answer rTrue! R is bits or bytes per second, so if a packet is L bits/bytes long, and it passing the transmission link at rate 1/a seconds... T/F: In a virtual-circuit packet-switched network, a packet switch maintains state information for each connection passing through the router. - correct answer True! Parts that make up network delay. - correct answer Queuing Delay - Transmission Delay- Processing Delay- Propagation Delay- Ethernet runs on what media: - correct answer rFiber Co-axial cables Unshielded twisted pair (UTP) Processes running on different hosts communicate using: - correct answer Messages Process running on a host machine is identified by: - correct answer host IP address and the associated port number TCP Service Provides: - correct answer Reliable Transport, Flow Control, Connection oriented, Congestion control UDP service: - correct answer Unreliable, used in gaming applications What is true for HTTP: - correct answer It can be both non-persistent and persistent, it uses tcp, and is stateless. HTTP 1.0 protocol supports following methods: - correct answer GET, HEAD, POST T/F: Connections in a UDP application starts with a 3-way handshake - correct answer FALSE! UDP is the sending of information with no handshake to a destination. This is why it is unreliable. 3-Way handshake has the following packet sequence: - correct answer1. SYN, 2. SYN-ACK, 3. ACK Assuming a single non-persistent connection, how long does it take to to download a very small object from a server? What about 3 very small objects? - correct answer1 object: 2 RTT (Round trip time) 3 objects: 6 RTT Which DNS record gives the IP of a host? - correct answer 'A' T/F: Consider an HTTP Web server using persistent connections. Suppose the server spawns a separate process for each client that connects to the server. Then each of these spawned processes will have different server port numbers. - correct answer False! The server uses the client side ip and port to determine what to respond to and where to send a response. T/F: Suppose that host A wants to send data over TCP to host B, and host B wants to send data to host A over TCP. Two separate TCP connections - one for each direction - are needed. - correct answer False! Once a three way handshake is established, data can be transmitted in both directions. A HTTP server has two types of sockets. Name and describe them. - correct answer Passive socket is one that is set up and is just listening for connections, and will establish one when found. Active socket is one that actually does data transfer. What is the TCP/UDP checksum of the following two numbers 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 - correct answer add all bits, carry ones left over around and add again, and one's compliment. In the 'rdt' protocol developed in the class, what is the purpose of the sequence number? - correct answer To handle duplicates. If a packet of the same sequence number is found, the receiver can throw it out. In the 'rdt' protocol developed in the class, what is the purpose of the timer? - correct answer The timer serves the purpose of monitoring not yet acknowledged segments. If a segment reaches a timeout before being acknowledged, it will be re transmitted. In SR (Selective Repeat) protocol, is it possible for the sender to receive ACK for a packet that is outside of the current window. (packets 1,2,3,4,5,6,7,8,9.... window size is 3, current window is 7,8,9. Is it possible to receive ACK for 1 or 2 or ... or 6 at sender? Consider ACK losses, retransmission and duplicate ACKs) Please explain. - correct answer Yes, in Selective Repeat the receiver's window is not linked to the sender's acknowledgement window. So if, for instance, a packet were to delay past the RTT time for that sequence, but was not lost, and another packet and acknowledgement were to get back beforehand, then an ACK could arrive for a packet outside of the current window. Knowing that TCP uses a 32-bit sequence number field, what is the maximum size of file that can be transmitted over a single TCP connection? show your work.. - correct answer2^32 bit / 8 bits per byte = bytes = ~ 535 Megabytes Host A and Host B are communicating over a TCP connection. Host B has already received 130 bytes from Host A. Now Host A sends two more segments back to back containing 30 and 80 bytes respectively. 1. What is the sequence number of the first segment? 2. What is the sequence number of the second segment? - correct answer1. 131 2. 161 TCP assigns a sequence number to each segment that is being sent. The sequence number for each segment is the number of the _______ byte carried in that segment. - correct answer First. The value of the acknowledgment field in a segment defines the number of the ______byte a receiver expects to receive. - correct answer Next! If the ACK value is 200, then which byte has been received successfully. - correct answer199 The value of window size is determined by _________. - correct answer the reciever Connection establishment in TCP is called __________ handshaking - correct answer3-way handshaking In TCP, the receiver can temporarily shut down the window; the sender, however, can always send a segment of _____ byte(s) after the window is shut down. - correct answer one ACK segments consume _______ sequence number(s) and are they acknowledged? - correct answer0; they are not "store-and-forward" technology is used by - correct answer packet switched networks Complexity in the internet is at the ________ of the network. - correct answer edge!!!!! Encapsulation and decapsulation is a process of adding and removing ______ to the messages. - correct answer headers in the 5 layer network we are studying in the class, name the layers in the correct order - correct answer Application Transport Network Data Link Physical Name the two layers implemented only at the end hosts. - correct answer Application layer and Transport layer, layers 5 and 4. Two main attributes that measure the performance of a network are.... - correct answer Throughput and Delay T/F: Throughput measures the number of useful bits delivered at the receiver, and is different from but related to to the bandwidth of the link. - correct answer True! Consider a 125 KB file that needs to be sent through a network path. The bandwidth of the path is 1 Mbps. The one way delay between sender and receiver is 20 ms. Suppose the sender continuously sends data at the bandwidth rate, and no packets are lost, no retransmissions. How long does it take to send the file? And the throughput of the network is? 1KB = 1000Bytes - correct answer125* 1000 * 8 = 1000000 bits or 1 Mb So on a path with bandwidth 1Mbps ( 1 Mb per second) it would take roughly 1 second to transmit the file. The throughput of the network is 1 Mbps.