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23 Cards in this Set
- Front
- Back
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How does the data-link layer prepare packets for transmission?
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It encapsulates with a header and a trailer to create a frame.
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Describe four general data link layer media access methods
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Controlled (like ring topology), or contention-based (compete for use). In point-to-point connections they can be half duplex (only one node can transmit at a time) or full duplex (can transmit and receive at same time)
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Describe the features of a logical ring topology
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Each node in a ring receives a frame, and it passes it along if it is not for that host. If there is no data being transmitted, a signal (known as a token) can be placed on the media. A node can place a frame on the media only when it has the token, this is a controlled media access control technique called token passing.
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Name five layer two protocols
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Ethernet, PPP, High-level data link control (HDLC), frame-relay, and ATM
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List 5 header field types in data link frames
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Start, Source-destination address, priority (QoS), Type, Logical connection control, physical link control, flow control, congestion control
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If a node receives a frame and the calculated CRC does not match the CRC in the FCS, what action will the node take?
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It will drop the frame
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Which of the following protocols are typically used in WANs?
A) 802.11 B) Ethernet C) HDLC D) PPP |
HDLC and PPP. The others are LAN protocols.
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What are the contents of the data field in a frame?
64 bytes, the network data layer PDU, the layer 2 source address, the data directly from the application that generated the data? |
The correct answer is network data layer PDU, which is encapsulated in the frame.
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Which of the following is characteristic of contention-based MAC?
Used on non-shared media, nodes compete for use of the medium, leaves MAC to the upper layer, each node has a specific time to use the medium. |
Nodes compete for the medium
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Which of the following are common data link sublayers used in LANs? (Choose two)
Protocol data unit, Logic Link Control, MAC, network interface card, carrier access multiaccess. |
Logic Link Control and MAC. LLC is the upper sublayer and MAC is the lower sublayer.
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Which of the following describes a virtual circuit?
A) Is an error detection technique B) Provides an encapsulation technique C) Is used only with point-to-point topologies D) Establishes a logical connection between two network devices |
D. Virtual circuits establish a logical connection between two devices to provide a logical point-to-point topology. Virtual circuits can be used over multiple types of physical topologies.
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Three basic parts that are common to all data link layer frames?
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Header, data and trailer
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Which of the following functions does the data link layer perform?
Provides user interfaces, ensures end-to-end delivery of data between hosts, connects the network software to the network hardware, establishes and maintains sessions between applications |
Provides the connection between hardware and software. User interfaces is the role of the application layer, and end-to-end delivery is the role of the network layer.
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Which of the following is true about the logical topology of a network?
Is always multiaccess, provides the physical addressing, is determined by how the nodes in the network are connected, influences the type of MAC used in the network |
The logical topology influences MAC
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Wireless uses what to avoid collisions?
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CSMA/CA
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Token-ring is deterministic or nondeterministic?
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Deterministic
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Contention-based access is deterministic or nondeterministic?
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Nondeterministic
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What does MAC provide to the data link layer?
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Provides data link layer addressing and delimiting of data according to the physical signaling requirements of the medium and the type of data link layer protocol in use
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Ethernet uses what to avoid collisions?
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CSMA/CD
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LLC stand for what and does what?
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Logical Link Control - places information in the frame that identifies which network layer protocol is being used for the frame
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What are the two sublayers of the data link layer?
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The upper sublayer defines the software processes that provide services to the network layer protocols, and the lower sublayer defines the media access processes performed by the hardware
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A backoff procedure is for what purpose?
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To avoid wireless collisions
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The frame begins with a _________________ and Start of Frame (SOF) indicator and ends with a ____________________ .
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Preamble and a cyclic redundancy check (CRC)
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