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ICND1 – TCP & UDP Questions

June 25th, 2017 in ICND1 100-105 Go to comments

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Question 1

[am4show have=’p2;’]Which of the following are types of flow control? (Choose three)

A. buffering
B. cut-through
C. windowing
D. congestion avoidance
E. load balancing

 

Answer: A C D[/am4show]

Explanation

Three types of flow control are buffering, windowing & congestion avoidance:

+ Buffering: If a device receives packets too quickly for it to handle then it can store them in a memory section called a buffer and proceed them later.

+ Windowing: a window is the quantity of data segments that the transmitting device is allowed to send without receiving an acknowledgment for them. For example:

With the window size of 1, the sending device sends 1 segment and the receiving device must reply with 1 ACK before the sending device can send the next segment. This “waiting” takes some time.

By increasing the window size to 3, the sending device will send up to 3 segments before waiting an ACK -> helps reduce the waiting time.

+ Congestion avoidance: lower-priority traffic can be discarded when the network is overloaded -> minimize delays.

Question 2

[am4show have=’p2;’]A receiving host has failed to receive all of the segments that it should acknowledge. What can the host do to improve the reliability of this communication session?

A. decrease the window size
B. use a different source port for the session
C. decrease the sequence number
D. obtain a new IP address from the DHCP server
E. start a new session using UDP

 

Answer: A[/am4show]

Question 3

[am4show have=’p2;’]What must occur before a workstation can exchange HTTP packets with a web server?

A. A UDP connection must be established between the workstation and its default gateway.
B. A UDP connection must be established between the workstation and the web server.
C. A TCP connection must be established between the workstation and its default gateway.
D. A TCP connection must be established between the workstation and the web server.
E. An ICMP connection must be established between the workstation and its default gateway.
F. An ICMP connection must be established between the workstation and the web sewer.

 

Answer: D[/am4show]

Explanation

HTTP is based on TCP connection so a TCP connection must be established first between the workstation and the web server.

Question 4

[am4show have=’p2;’]How does TCP differ from UDP? (Choose two)

A. TCP provides best effort delivery.
B. TCP provides synchronized communication.
C. TCP segments are essentially datagrams.
D. TCP provides sequence numbering of packets.
E. TCP uses broadcast delivery.

 

Answer: B D[/am4show]

Explanation

Before two computers can communicate over TCP, they must synchronize their initial sequence numbers (ISN) -> B is correct.

TCP uses a sequence number to identify each byte of data. The sequence number identifies the order of the bytes sent from each computer so that the data can be reconstructed in order, regardless of any fragmentation, disordering, or packet loss that may occur during transmission -> D is correct.

Question 5

[am4show have=’p2;’]What is the purpose of flow control?

A. To ensure data is retransmitted if an acknowledgement is not received.
B. To reassemble segments in the correct order at the destination device.
C. To provide a means for the receiver to govern the amount of data sent by the sender.
D. To regulate the size of each segment.

 

Answer: C[/am4show]

Question 6

[am4show have=’p2;’]Refer to the exhibit. A network technician has added host A to the network. Host A cannot communicate on the network. A ping that is issued on the host to address 127.0.0.1 fails. What is the problem?

pc_ping_fail.jpg

A. The router is not forwarding the ping packets to network 127.0.0.0.
B. The remote host at 127.0.0.1 is unreachable.
C. The default gateway is incorrect.
D. The IP address of host A is incorrect.
E. The TCP/IP protocols are not loaded.

 

Answer: E[/am4show]

Comments (13) Comments
  1. chuck
    July 30th, 2017

    Question 6. The TCP/IP protocols are not loaded??

  2. jde
    July 30th, 2017

    Question 6. I don’t understand why E is the correct answer?

  3. KL
    August 23rd, 2017

    to jde
    you can try the following steps in you computer
    1> from cmd line, you can ping 127.0.0.1 which is your loopback address
    2> go to network connections,
    3> click the LAN and un-select the TCP/IPv6 and TCP/IPv4
    4> no you are not able to ping 127.0.0.1 from cmd line.

  4. Hyatt
    September 23rd, 2017

    Hi, could someone please explained to me Question 6 answer of E and not C?

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    November 2nd, 2017

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  6. quanghuy147
    January 5th, 2018

    Hi Hyatt,
    To my understanding, 127.0.0.1 is the local loopback address, one of the purposes of that address is to test TCP/IP stack on the local computer. It is not an address for routing.

    If you can ping 127.0.0.1 , it means your TCP/IP stack is good but it only ‘local’, which means it does not guarantee you are connected to other devices.

    **By ‘local’ I mean ‘within the host only’ .

  7. JamesX
    May 15th, 2018

    That is correct. When you ping 127.0.0.1 you are pinging the Local Loopback in the physical machine. This is meant to test the local machine so the signal never goes out onto the media. If you disconnected the Ethernet cable from your computer you would still be able to ping 127.0.0.1

  8. Neemaamaparri
    May 23rd, 2018

    Question 6 is very helpful which justifies that the ping 127.0.0.1 command from the host helps in testing its own tcp/ip protocol stack.

  9. alberthdr
    July 15th, 2018

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  10. Pkay
    August 12th, 2018

    Where can I find the questions for these answers. I cannot find them. Please help me.

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    August 15th, 2018

    Get a membership Pkay. I was in the same boat.

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