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Flashcards

NetAcad 14 & 15

Scott Jones Computer Networking IT Certification English 127 cards

Cards in this deck (127)

  1. 1What does the transport layer do with application layer data?It moves it from source to destination.
  2. 2Data in transit is known as what?A conversation
  3. 3In what layer are conversations traced?Transport layer
  4. 4Packets can only hold so much data, how do networks get around this problem?TCP divides data into segments, and UDP splits data into datagrams.
  5. 5What is conversation multiplexing?It is when multiple applications can use the network at the same time. The data must be segmented first and only one PDU will cross the wire in each direction at any give time.
  6. 6TCP is full-duplex or half-duplex?Full-duplex
  7. 7What is the primary purpose of TCP?Segments can become lost, it ensure their delivery.
  8. 8How does TCP ensure same-order delivery?It divides data into segments, and number and sequence them.
  9. 9What can cause data to not arrive to in the correct order?Data can take different routes to its destination, and the transmission rates may vary.
  10. 10The resources of a receiving host are overwhelmed, rather than retransmitting data and increasing network traffic, what can TCP do?Flow control. TCP will regulate the amount of data the source is transmitting.
  11. 11TCP What happens once data has arrived?The destination device sends an acknowledgement to the source.
  12. 12How does TCP track the state of each session?It records what data has been send and what has been acknowledged.
  13. 13UDP is a connectionless protocol, explain.It does not establish a handshake; there is no connection between the sender and the host. It does not know whether the receiver is ready, nor whether it exists.
  14. 14UDP is a stateless protocol, explain.It does not track the data sent and it has no way of knowing if it was received.
  15. 15UDP is a best-effort delivery protocol, explain.There is no acknowledgement that the data has been received at the other end.
  16. 16Why does a UDP header have fewer fields?It does not manage reliability and flow control.
  17. 17What makes UDP faster than TCP?The UDP header has fewer fields, it does not track data, nor does it establish a handshake.
  18. 18Data is divided into... TCP - UDP -TCP - Segments
    UDP - Datagrams
  19. 19TCP or UDP DHCPUDP
  20. 20TCP or UDP DNSUDP
  21. 21TCP or UDP Simple Network Management ProtocolUDP
  22. 22TCP or UDP DNSUDP
  23. 23Why is UDP an optimal protocol for transmitting VoIP data?Retransmissions of lost data with TCP would slow down the delivery and make voice communications lag.
  24. 24TCP or UDP HTTPTCP
  25. 25TCP or UDP FTPTCP
  26. 26TCP or UDP SMTPTCP
  27. 27TCP or UDP SSHTCP
  28. 28Data is being transmitted, it is ok for some data to be dropped, but there must be minimal delay. Should you use TCP or UDP?UDP
  29. 29Protocols that do not require error detection, flow control, acknowledgements, and error recovery should use TCP or UDP?UDP
  30. 30When data needs to come through in a specific order, would TCP or UDP be best?TCP
  31. 31How does TCP work with video streaming such as watching a movie?It uses buffering, bandwidth probing, and congestion control to ensure all data is transmitted. You do not want to lose any data when watching the movie. When the segments are in order and sufficient bandwidth is restored, the movie will resume playing.
  32. 32How many bytes is the TCP header?20 bytes.
  33. 33The TCP checksum field is for what?Error checking.
  34. 34What size is a UDP header?8 bytes
  35. 35What is a source port number?A port number dynamically generated by the host OS. It identifies the data in transit.
  36. 36What is a destination port?A port number identifying the type of service being requested from a server.
  37. 37A socket pair is a combination of what?The source IP address & source port number. (A socket)
    and
    The destination IP address & destination port number. (A socket)
    These two sockets are a socket pair.
  38. 38How is the source port number important to the application layer?It uses the source port number as a return address.
  39. 39Who determines how port numbers are assigned?The Internet Assigned Numbers Authority (IANA)
  40. 40What are well-known ports used for?Common services and application such as web browsers, email clients, and remote access clients.
  41. 41What is the well-known ports range?0 to 1023
  42. 42What are registered ports used for?They are used by vendors for their distributed applications. The IANA will assign a port number.
  43. 43Private - Dynamic ports used for?Identifying the client application during communication.
  44. 44What is the registered port range?1024 to 49,151
  45. 45What is the private port range?49,152 to 65,535
  46. 46What does the netstat command do?It will show active TCP connections. Unexplained connections may pose a security risk.
  47. 47Why does TCP initiate a handshake?To validate the destination host is available to communicate.
  48. 48Explain the three-way TCP handshake process.1 - Client sends SYN request to server.
    2 - Server ACK the session and sends back a request for a server to client communication session.
    3 - The clients sends an ACK to the server.
  49. 49TCP A session termination is a two-way or three-way handshake process?Two-way.
  50. 50Explain the TCP session termination process.1 - Client sends a segment with the control flag set to FIN.
    2 - The server acknowledges.
    3 - Server sends its onw FIN.
    4 - Client acknowledges.
  51. 51What is the control flag used for in the TCP header?It determines the purpose of the segment. For example, a FIN to initiate a session termination.
  52. 52TCP Control Flag URGThe data should be prioritised.
  53. 53TCP Control Flag ACKAcknowledge connection establishment and session termination.
  54. 54TCP Control Flag PSHData should be pushed immediately to the application instead of buffering.
  55. 55TCP Control Flag RSTReset the connection when an error or timeout occurs.
  56. 56TCP Control Flag SYNSynchronise sequence numbers used in the connection establishment.
  57. 57TCP Control Flag FINDo not sent any more data. Terminate the session.
  58. 58What values are used to represent what the control flag does?A sequence of binary values.
  59. 59What is the purpose of sequence numbers?It allows data to be reassembled in the original order.
  60. 60The sequencing of transmitted data has an ISN, what is this?The initial sequence number of the conversation. It is randomly generated and helps prevent malicious attacks.
  61. 61What is a receiving buffer?This is where the TCP organises the data into proper sequence order before being sent to the application layer.
  62. 62What is an exceptional acknolwedgement?It is the next byte the receiver expects to receive. This is placed in the ACK field when the receiver is acknowledging segments it receives.
  63. 63What are sequence numbers?The first byte of data in the segment being transmitted.
  64. 64Why are exceptional acknowledgements not efficient?If a segment fails to send, many of the already sent ones will be retransmitted again.
  65. 65What is selective acknowledgement (SACK)?Negotiated during the three-way handshake. It allows the receiver to acknowledge the specific segments it receives, the sending host only needs to retransmit the missing data.
  66. 66How does TCP decide how long to wait before resending a segment which has not been acknowledged.A timer.
  67. 67What is the maximum window size?The maximum number of bytes that can be transmitted without an ACK coming through.
  68. 68Data segments are transmitting a web page. When will an ACK come through?Usually after 2 segments, but always before the window size is reached.
  69. 69Managing the amount of data that the destination can receive and process reliably is a method of what?Flow control.
  70. 70What does the sliding windows protocol allow?It is when the device requesting the data can modify the window size depending on buffer availability.
  71. 71What is TCP window scaling?The window size can increase with successful acknowledgements.
  72. 72Does TCP on the destination, or source determine the window size?The destination side.
  73. 73What is the maximum segment size?The maximum number of bytes allowed in a single TCP segment.
  74. 74What is the default MSS size?1460 bytes.
  75. 75What can TCP do to manage congestion?Reduce the number of byte it sends before receiving an ACK.
  76. 76What does the application layer do?Provides an interface between the application and the underlying network.
  77. 77What OSI layer is responsible for formatting, compressing, and encrypting data for transmission?The Presentation layer.
  78. 78What does the OSI session layer do?Handles the exchange of information. It keeps sessions active and restarts them if they are disrupted or idle too long.
  79. 79What port does DNS use?53
  80. 80What ports to DHCP use?Client 68, and Server 67
  81. 81What port does SMTP use?25
  82. 82What port does POP3 use?110
  83. 83What port does IMAP use?143
  84. 84What ports do FTP use?20, 21
  85. 85What ports do HTTP use?80 and 8080
  86. 86What port does HTTPS use?443
  87. 87What is the client-server model?The client requests a service and the server provides it.
  88. 88What is a peer?Any connected end device capable of functioning as a server and client.
  89. 89What is a peer-to-peer network?It is when data is accessed from a peer instead of a dedicated server.
  90. 90BitTorrent What is a swarm?Peers obtain data from multiple peers at the same time.
  91. 91What is a torrent file used for?To locate peers who have what you need.
  92. 92What request does a client send to a web server?A GET request.
  93. 93How does a web server respond to a request it can fulfil.It sends a (200) OK message.
  94. 94What are two message types used by HTTP when uploading to a web server.POST and PUT
  95. 95How are HTTP GET requests not secure?They are in plaintext, which means they can be interpreted.
  96. 96What makes HTML pages unsecure.The pages are unencrypted.
  97. 97What protocol encrypts data streams on HTTPS?Transport Layer Security
  98. 98Does HTTPS authenticate data?Yes
  99. 99SMTP is the abbreviation for...Simple Mail Transfer Protocol
  100. 100What is SMTP used for?Sending emails.
  101. 101What port does SMTP use?Port 25
  102. 102What does SMTP do if the destination email server is offline or busy?It will spool the message back and send it later. The server will check periodically and send it as soon as possible.
  103. 103An SMTP server has spooled an outgoing email, and the expiry time has been reached. What happens to the email?It is returned to sender.
  104. 104POP3 is the abbreviation for...Post Office Protocol 3
  105. 105What is POP used for?Retrieving emails from an email server.
  106. 106What will POP do with emails on a server once they have been downloaded?It deletes them.
  107. 107IMAP is the abbreviation for...Internet Message Access Protocol
  108. 108An email is only deleted from an IMAP server when...The client deletes it on their email application.
  109. 109What is IMAP used for?Downloading your emails from the server as copies.
  110. 110DNS Records What is A?An end device IPv4 address.
  111. 111DNS Records What is NS?An authoritative name server.
  112. 112DNS Records What is AAAA?An end device IPv6 address.
  113. 113DNS Records What is MX?A mail exchange record.
  114. 114What does the following command do? ipconfig /displaydnsShow the cached DNS entries stored in memory.
  115. 115What are DNS top-level domains?It is where the DNS request will initially go through. Businesses, countries, and educational institutes etc will use different domains.
    (.com .edu .gov .fr)
  116. 116When a DNS request reaches the correct top-level domain, where does it go next?The second level domain. For example, cisco.com. DNS then sends the IP address of the web server of the domain back to the sender.
  117. 117What does the nslookup command do?Show the default DNS server configured on your PC.
  118. 118On a home network, where would the DHCP server typically be located?The router provides this service.
  119. 119What is the main difference between DHCP and DHCPv6?DHCPv6 does not configure the device with a default gateway address. This must be obtained dynamically from the router advertisement message.
  120. 120What message will a client broadcast to locate the DHCP server?DHCPDISCOVER
  121. 121What is a DHCPOFFER message?It is when the DCHP server responds to a discover message. It will offer the device addressing information.
  122. 122What does the DHCPREQUEST broadcast do?The client will choose an offer (if there is more than one DHCP server) and send back the request message to the chosen server.
  123. 123What are common DHCPv6 messages?SOLICIT
    ADVERTISE
    INFORMATION REQUEST
    REPLY
  124. 124What does an FTP server do?It allows data to be exchanged from one computer to another.
  125. 125What are the two connections made to the FTP server?The first is for control traffic using TCP port 21.
    The second connection on TCP port 20 is where data is transferred.
  126. 126What does the server message block protocol do?Provides shared access to files, printers, and servers across a network.
  127. 127What do Linux and Unix use to share resources with Microsoft networks? What about Mac OS?SAMBA
    SMB

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IT Certification Computer Networking Flashcards on NetAcad 14 & 15, created by Scott Jones on 24/12/2022.
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