Chapter 4: Data Link Layer Flashcards
Remember the name of error detection technies - The Data Link layer is responsible for communications between end-device network interface cards - It allows upper layer protocol to access the physical layer media and encapsualtes Layer 3 packets (IPv4 and IPv6) into Layer 2 Frames. - It also performs error detection and rejects corrupted frames. - The data link layer does not specify the type of connections and electrical signals, radio waves, or light pulses - that is the physical layer. - Err (20 cards)
As part of the five-layer network model used in this textbook, the data link layer sits directly between which layer?
The physical and network layers
Which of the following true with respect to the data link layer?
a. It accepts streams of bits from the application layer
b. It is responsible for encoding the bit-stream as a series of elctronic voltages
c. It performs error detection
d. It performs routing functions
e. It organises data from the physical layer and passes these coherent messages directly to the application layer
c. It performs error detection
Which of these is not a function of data link protocol:
a. Media acces control
b. Message delineation
c. Amplitude shift keying
d. Indicating when a message starts and stops
e. Error control
c. Amplitude shift keying
In general, controlled approaches:
a. work better than contention approaches for small networks that have low usage.
b. work better than contention approaches for large networks that have high usage.
c. work better than contention approaches for all sizes of networks.
d. do not require a host, server, or active monitor to assign media access control.
e. have many collisions
b. work better than contention approaches for large networks that have high usage.
The two sublayers of the data link layer consist of the media access control sublayer and ?
Logical link control sublayer
What of the following media is least susceptible to noise?
a. Fiber optic cable
b. Coaxial cable
c. Twisted pair
d. Unshielded twisted pair
e. Shielded twisted pair
a. Fiber optic cable
What is the primary source of error in data communication?
Spikes
What can obliterate a group of bits, causing a burst error?
Impulse noise
Cross-talk:
a. occurs when one circuit picks up signals in another
b. is always bothersome because it has a high signal strength
c. decreases with increased proximity of two wires
d. decreases during wet or damp weather
e. increases with lower frequency signals
a. Occurs when one circuit picks up signals in another
What is the loss of power a signal suffers as it travels from the transmitting computer to a receiving computer?
Attenuation
What is an effective way to prevent impulse noise, cross talk, and intermodulation noise?
Shielding wires
What is an effective way to prevent attenuation?
Adding repeaters or amplifiers to a circuit
Asynchronous transmission:
a. is used to transmit each character simultaneously with all other characters
b. has a pre-determined, fixed time between sending characters
c. is typically used on multipoint half duplex circuits
d. uses a continuous series of start bits as an idle signal
e. each character is transmitted independently of all other characters
e. Each character is transmitted independently of all other characters.
Which of the following is not a type of synchronous protocol?
a. SDLC
b. VT100
c. HDLC
d. Ethernet
e. PPP
b. VT100
Which of the following is true about the data link protocol, SDLC:
a. It is a client-server protocol, developed by Compaq in 1996
b. It transmits each character independently of one another and includes start and stop bits for each character sent
c. It uses a special bit pattern called a flag at the beginning and end of every frame (or packet)
d. It uses a contention media access control protocol and is used in most LANs today
e. it does not have any error detection capabilities
c. It uses a special bit pattern called a flag at the beginning and end of every fram (or packet)
Which of the follow is true about the data link protocol, Ethernet (EEE 802.3):
a. It is not veyr popular
b. It is a bit-oriented protocol
c. It uses block check characters for error detection
d. Newer version permits jumbo frames.
e. It uses parity bits for error detection
d. Newer version permits jumbo frames
A blank is a software-enabled technique that can change the hardcoded MAC address to any MAC address and thus overcome MAC address filtering:
a. MAC address spoofing
b. MAC address engaging
c. Ethernet address regeneration
d. Address regeneration
e. MAC address cheesing
a. MAC address spoofing
What are the error detection techniqes in the Data Link Layer
- Parity Check
- Checksum
- Cyclic Redundancy Check (CRC)
What is the basic Unit of Information for the Data Link Layer
Frame
Three important functions of the Data Link Layer
- Provides an Interface to the Network Layer
- Error Control
- Flow Control
