Chapter 5 - TCP/IP (Questions/Answers)

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Chapter 5 - TCP/IP (Questions/Answers)

Questions and Problems
Section 5.2

1. What are the four layers of the TCP/IP model?
     i. Application – Defines the applications used to process requests and what ports and sockets are used.
          I. (This layer is used to process requests from hosts and to make sure a connection is made to an appropriate port.)
     ii. Transport – Defines the type of connection established between hosts and how acknowledgements are sent.
     iii. Internet – Defines the protocols used for addressing and routing the data packets.
     iv. Network Interface – Defines how the host connects to the network.

2. Which layer of the TCP/IP model processes requests from hosts to make sure a connection is made to the appropriate port?
     i. Application Layer

3. What are well known ports?
     i. Also known as “reserve ports”, which are ports 1 – 1023 that are reserved by ICANN (Internet Corporation for Assigned Names and Numbers).

           Port Number Assignments
        Port Numbers          Description
           1 - 1023          The “well known” ports
       1024 – 49,151            Registered ports
      49,152 – 65,535        Private Ports

4. Identify the port numbers for the following applications.
     a. Telnet – 23
     b. HTTP – 80  (Hypertext Transfer Protocol)
     c. FTP – 20, 21 (File Transfer Protocol)
     d. DNS – 53 (Domain Name Server)
     e. DHCP – 67, 68 (Dynamic Host Control Protocol)

      Common Applications and Their Port Numbers
    Port Number                        Application Description
       20, 21                                            FTP - (File Transfer Protocol)
          22                                            SSH - (Secure Shell)
          23                                          Telnet - (Virtual Terminal Connection)
          25                                           SMTP - (Simple Mail Transfer Protocol)
          53                                               DNS  - (Domain Name Server)
       67, 68                                           DHCP  - (Dynamic Host Control Protocol)
          69                                            TFTP  - (Trivial File Transfer Protocol)
          80                                            HTTP  - (Hypertext Transfer Protocol)
         110                                            POP3  - (Post Office Protocol)
         161                                            SNMP  - (Simple Network Management Protocol)
         443                                           HTTPS  - (Secure HTTP)
         445                                            SMB    - (Server Message Block)
        1701                                            L2TP  - (Layer 2 Tunneling Protocol)
        1720                                       H.323/Q.931  - (Voice Over Protocol)
        1723                                            PPTP  - (Point-To-Point Tunneling Protocol)

5. Define the purpose of a connection oriented protocol. Give an example.
     i. Establishes the network connection, manages the data transfer, and terminates the connection.
          I. Connection Oriented Protocol – Establishes a network connection, manages the delivery of data, and terminates the connection.
     ii. The TCP (Transport Control Protocol) protocol within the TCP/IP transport layer.
          I. TCP protocol establishes a set of rules or guidelines for establishing the connection.

6. What three packets are exchanged between two hosts when establishing a TCP connection?
     i. SYN – (Synchronizing Packet)
     ii. SYN ACK – (Synchronizing Acknowledgement Packet)
     iii. ACK– (Acknowledgement Packet)

7. What is the purpose of a sequence number (SEQ=) in TCP data packets?
     i. SEQ (Sequence Number) is used to keep track of the data packets being transferred from Host A to Host B.

8. Explain how a host knows whether a data packet was not received
     i. A SYN ACK packet is sent back to the host– The ACK is an acknowledgement that Host B received the pack from Host A. There is a number attached to the ACK with a value of (x+1) [where “x” is the SEQ (Sequence Number).] that should be the sum of the SEQ# from packet 1 plus the length (LEN) of packet 1.

9. Describe how a TCP connection is terminated.
     i. The host sends a FIN (Finish) packet to the other connected host.
          1. Host B sends a FIN packet to Host A indicating the data transmission is complete.
          2. Host A responds with an ACK packet acknowledging the reception of the FIN packet.
          3. Host A then sends Host B a FIN packet indicating that the connection is being terminated.
          4. Host B replies with an ACK packet.

10. What is a connectionless protocol? Give an example.
     i. UDP (User Datagram Protocol) Protocol is a connectionless protocol.
     ii. UDP packets are transported over the network without a connection being established and without any acknowledgment that the data packets arrived at the destination.

11. What is the purpose of the Internet layer in the TCP/IP protocol suite?
     i. It defines the protocols used for addressing and routing the data packets.
          I. Examples – IP, ARP, ICMP, & IGMP.
               1. IP (Internet Protocol) – Defines the addressing used to identify the source and destination addresses of data packets being delivered over an IP network
               2. ARP (Address Resolution Protocol) – Used to map an IP address to its MAC address.
               3. ICMP (Internet Control Message Protocol) – Used to control the flow of data in the network, for reporting error, and for performing diagnostics.
                    a. Contains “Ping” (packet Internet groper) troubleshooting tool.
               4. IGMP (Internet Group Message Protocol) – Used when one host needs to send data to many destination hosts.
                    a. This process is called Multicasting.
                    b. Example - Streaming (audio and video) - data is sent without waiting for an acknowledgement that the data packets were delivered.

12. What is the purpose of an ARP request?
     i. A BROADCAST message is sent to all networking devices asking which network interface has the specific IP address detailed in the ARP query that was sent.
          I. ARP – is used to resolve an IP address to a hardware address for final delivery of data packets to the destination. ARP issues a query in a network called an ARP request asking which network interface has this IP address

13. What is the purpose of an ARP reply?
     i. A reply from the host assigned the IP address replies with an ARP reply.
          I. ARP Reply - The protocol that contains the hardware address (MAC address) for the destination host that sent the ARP request.

14. What important networking –troubleshooting tool is part of ICMP, and how does it test a network connection?
     i. Ping – Packet Internet Groper
          I. The ping command uses a series of echo requests, and the networking device receiving the echo requests responds with a series of echo replies to test a network connection.

15. When is IGMP used?
     i. IGMP is used when multicasting (when one host wants to send data to many destination hosts). The source doesn’t care whether the destination receives a packet.
          I. Example – Steaming audio and video files over the internet.

16. The network interface layer of the TCP/IP model defines how the host connects to what network?
     i. Ethernet, Token-Ring network, or a router connected to a frame relay wide area network.
          I. Not dictated by the TCP/IP protocol
          II. Every TCP/IP data packet must have a destination and source MAC address in the TCP/IP header.

Section 5-3

                     128 –  64 –  32 –  16 – 08  –  04 –  02   – 01
                     ___ -____-____-____-____-____- ____ -____

17. Convert the following 8-bit binary number to decimal: 10010011?
     i. 147

18. Convert the following octet to decimal: 11000000?
     i. 192

19. Convert the following 8-bit number to decimal 11111100?
     i. 252

20. Convert the following binary number to decimal 11111111?
     i. 255

21. Convert the number 192 to its binary equivalent?
     i. 11000000

22. Convert the number 65 to its binary equivalent?
     i. 01000001

23. Convert the number 96 to its binary equivalent?
     i. 01100001

24. What is the equivalent hexadecimal number for 13?
     i. 1101

25. Convert 0x5AF3 to binary. Use Table 5-5.
     i. 0101101011110011

26. Convert 1011011011110001 to hexadecimal.
     i. B6F1

Section 5-4

27. What is the IP address range for class C addresses?
     i. –

28. What is the purpose of class D IP addresses?
     i. Reserved for Multicast groups
          I. Example – Skype for video conferencing

29. How many bits are in an IPv4 address? How many octets?
     i. Bits – 32

Example –     {xxxxxxxx}     |          {xxxxxxxx}          |         {xxxxxxxx}           |          {xxxxxxxx}
               1,2,3,4,5,6,7,8   |  9,10,11,12,13,14,15,16 | 17,18,19,20,21,22,23,24 | 25,26,27,28,29,30,31,32

     ii. Octets – 4
          I. Example - xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
                                1           2          3          4

30. The IP address is typically expressed in what format for the user?
     i. A dotted-decimal format.
          I. Example – X.X.X.X

31. The IP address is an example of what format?
     i. Dotted decimal format and is a Class C network.

32. How many network bits are in each of the following classes?
     i. Class A – 8 Network bits and 24 Host Bits
     ii. Class B -  16 Network bits and 16 Host Bits
     iii. Class C – 24 Network bits and 8 Host Bits

33. How many network and host bits are in a class C network address?
     i. 24 Network bits and 8 Host Bits

34. What is the purpose of a private IP address?
     i. Have been set aside for private use.
          I. Are not used for Internet data traffic but are intended to be used specifically on internal networks called intranets.

35. Can private IP address be routed?
     i. No, They  are Non- Internet Routable IP Addresses and not routed on the internet
          I. Non- Internet Routable IP Addresses - IP addresses not routed on the internet and are blocked by the ISP.

36. How are private IP addresses handled on the Internet?
     i. They are blocked by the ISP.

37. What organization assigns IP addresses?
     i. The ARIN (American Registry for Internet Numbers)
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