Layer Function Specifics

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  1. Provides a user interface
    Application Layer
  2. • Presents data
    • Handles processing such as encryption
    Presentation Layer
  3. • Keeps different applications’
    • data separate
    Session Layer
  4. • Provides reliable or unreliable delivery
    • Performs error correction before retransmit
    Transport Layer
  5. • Provides logical addressing,
    • which routers use for path determination
  6. • Combines packets into bytes and bytes into frames
    • Provides access to media using MAC address
    • Performs error detection not correction
    Data Link
  7. • Moves bits between devices
    • Specifies voltage, wire speed,
    • and pin-out of cables
  8. Acts as an interface between the application program
    Application Layer
  9. Responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exist.
    Application Layer
  10. It presents data to the Application layer and is responsible for data translation and code formatting.
    Presentation Layer
  11. Tasks like data compression, decompression, encryption, and decryption are associated
    with this layer.
    Presentation Layer
  12. Provides dialogue control between
    devices, or nodes.
    Presentation Layer
  13. It coordinates communication between systems and serves to organize their communication by offering three different modes: simplex, half duplex, and full duplex.
    Session Layer
  14. Segments and reassembles data into a data stream.
    Transport Layer
  15. Can establish a logical connection between the sending host and destination host on an internetwork.
    Transport Layer
  16. It also hides details of any network-dependent information from the higher layers by providing transparent data transfer.
    Transport Layer
  17. TCP and UDP both work at this layer.  Which protocol is reliable and which is not reliable?
    Transport Layer.  TCP is reliable, UDP is not.
  18. Explain Connection-Oriented Communication
    Before a transmitting host starts to send segments down the model, the sender’s TCP process contacts the destination’s TCP process to establish a connection. What is created is known as a virtual circuit. This type of communication is called connection-oriented. During this initial handshake, the two TCP processes also agree on the amount of information that will be sent in either direction before the respective recipient’s TCP sends back an acknowledgment. With everything agreed on in advance, the path is paved for reliable communication to take place.  This virtual CKT setup is called overhead.
  19. Explain the three-way handshake concerning connection-oriented session.
    The first “connection agreement” segment is a request for synchronization.

    • The second and third segments acknowledge the request and establish connection
    • parameters—the rules—between hosts.

    The final segment is also an acknowledgment.

  20. Explain Flow Control
    Provides a means for the receiver to govern the amount of data sent by the sender.
  21. Flow Control happens at what layer of the OSI model?
    Transport Layer
  22. Protocols involved during Flow Control ensure...
    The segments delivered are acknowledged back to the sender upon their reception.

    Any segments not acknowledged are retransmitted.

    Segments are sequenced back into their proper order upon arrival at their destination.

    • A manageable data flow is maintained in order to avoid congestion, overloading, and
    • data loss.
  23. What criteria must be meet to consider a circuit communication session connection-oriented?
    A virtual circuit is set up (such as a three-way handshake).

    It uses sequencing

    It uses acknowledgments

    It uses flow control
  24. What protocol is being used if a connection is not setting up a virtual CKT?
  25. What are the two types of packets used at the Network Layer?
    Data Packets - Routed protocols: IP and IPv6

    Route-Update Packets - Routing Information Protocols (RIP), RIPv2, Enhanced Interior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF).
  26. What is the purpose of Routing-Update Protocols.
    Route-update packets are used to help build and maintain routing tables on each router.
  27. How to routers and switches affect domains.
    • Routers break up BCST domains
    • Switches break up collision domains.
  28. This layer provides the physical transmission of the data and handles error notification,
    network topology, and flow control.
    Data Link Layer
  29. This layer formats messages into pieces, each called a data frame, and adds a customized header containing the destination and source hardware address.
    Data Link Layer
  30. What is one of the primary functions of the Data Link Layer?
    It is responsible for the unique identification of each device that resides on a local network. (MAC addresses)
  31. What are the two sublayers of IEEE Ethernet Data Link Layer?
    • Logical Link Control (LLC)
    • Media Access Control (MAC)
  32. What is the purpose of MAC?
    It defines how packets are placed on the media.
  33. What is the purpose of LLC?
    Responsible for identifying Network-Layer protocols and then encapsulating them.
  34. Responsible for identifying Network-Layer protocols and then encapsulating them.
    The purpose of LLC
  35. It defines how packets are placed on the media.
  36. How does encapsulation work?
    • User information is converted to data.
    • Data is converted to segments.
    • Segments is converted to packets/datagrams
    • Packets/datagrams is converted to frames
    • Frames is converted to bits
  37. During the encapsulation process, what layers hosts what process?
    • Transport layer - Segment
    • Network layer - Packet
    • Data Link layer - Frame
    • Physical layer - Bits
  38. Which layer is responsible for, among other things, synchronizing bits, bandwidth usage and multiplexing strategies
    Physical layer (layer 1)
  39. Which layer is responsible for, among other things, logical topology, method of transmitting on the media, connection services and synchronizing transmissions.
    Data link layer (layer 2)

    MAC layer is responsible for logical topology and the method of transmitting on the media.

    LLC layer is responsible for connection services and synchronizing transmissions.
  40. What is physical addressing all about?
    This happens at layer 2, MAC addresses are examples of physical addressing, which is a 48 bit address assigned to a device; such as a NIC, printer, computer or mouse.  

    The MAC address is normally a hexadecimal value with the first half (24 bits) designated as vendor code or Organizationally Unique Identifier (OUI).  

    The second 24 bits are device ID or hex value the vendor has not used.
  41. What layer does MAC reside?  What are some of the services provided by MAC?
    • Layer 2 (Data link)
    • - physical addressing
    • - logical topology
    • - method of transmitting data on the media
  42. What layer does LLC reside? What are some of the services provided by LLC?
    • Layer 2 (Data link)
    • Connection services
    • - Flow control
    • - Error control
    • Synchronizing transmissions
    • - Isochronous
    • - Isochronous
    • - Synchronous
  43. How does flow and error control function within LLC services?
    • It is a connection service operating at layer 2 (Data link).
    • Flow control limits the amount of data a sender can send at one time.
    • Error control allows the receiver to inform the sender if a data frame was received or not.
  44. How does error notification work at the LLC level?
    The recipient mathematically calculates a checksum of data being received, if the checksum doesn't match it is assumed the data is corrupted and notifies the sender to send it again.
  45. What are the three methods of synchronizing transmissions?
    • Isochronous
    • Asynchronous
    • Synchronous
  46. Which layer is responsible for, among other things, logical addressing, switching, connection services, bandwidth usage, multiplexing strategies.
    Network layer (Layer 3)
  47. How does the network layer handle logical addressing?
    Similar to layer 2 using physical addressing to make forwarding decisions, the network layer uses logical addressing to make its forwarding decisions.
  48. What are the three common switching techniques used at the network layer?
    Packet switching or routing is where data streams are divided into packets which contains a header with a source and destination.

    Circuit switching dynamically brings up a dedicated communication link between two parties.

    Message switching divides the data stream into messages.  Method that is too slow for real-time applications.
  49. How does connection services function at layer 3.
    Similar to connection services within LLC at the data link layer; flow control or congestion control limits the amount of data the send can transmit.  Additionally, the network layer uses packet reordering sequence packets in order as they are sent.
  50. Which layer is responsible for TCP/UDP, windowing and buffering?
    Transport layer (Layer 4)
  51. What does TCP and UDP stand for?  Explain what they are.
    Transmission Control Protocol is a connection oriented transport protocol that provides reliable transmissions by detecting dropped segments and informing the sender so it can be retransmitted.  User Datagram Protocol is a connectionless transport protocol that provides unreliable transport by not informing the sender of dropped segments.
  52. What layer does windowing occur? What protocol uses windowing?
    • Layer 4 (Transport layer)
    • TCP
  53. Explain windowing and sliding windowing.
    TCP uses windowing acknowledge one or more segments sent.

    Sliding windowing is the technique used when the size of the window increases exponentially after each successful transmission until transmission is unsuccessful or configured limited is reached.
  54. What layer does buffering occur?  What is buffering?
    Transport layer

    Buffering is the use of memory to store segments if bandwidth isn't available.
  55. What is another transport protocol used at layer 4?
    Internet Control Message Protocol (ICMP) which is a utilities protocol used for trace route and ping.
  56. What happens at layer 5
    Sessions layer sets up, maintains and tears down sessions?
  57. What functions occur when setting up sessions at layer 5?
    • Check user credentials
    • Assign numbers to a session's comm flow
    • Negotiate services required during the session
    • Negotiate which device sends first
  58. What functions occur while maintaining a session at the sessions layer?
    • Transferring data
    • Reestablishing a disconnected session
    • Acknowledging receipt of data
  59. What layer advertises services?
    Application layer (Layer 7)
Card Set:
Layer Function Specifics
2016-03-23 14:11:16
Layer Function Specifics

Layer Function Specifics
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