Computer Networking: A Top-Down
Approach, CH5 UPDATED ACTUAL Exam
Questions and CORRECT Answers
LINK: link-layer implementation - CORRECT ANSWER - LINK: in every host in
network interface card
LINK: NIC - CORRECT ANSWER - LINK: network-interface card, has controller and
physical transmission
LINK: single bit parity - CORRECT ANSWER - LINK: detect single bit errors
LINK: 2D bit parity - CORRECT ANSWER - LINK: detect and correct single bit errors
LINK: error checking in link layer - CORRECT ANSWER - LINK: parity checking,
checksum, CRC
LINK: CRC - CORRECT ANSWER - LINK: cyclic redundancy check
D = data bits
G = generator
R = CRC code, remainder, length is G-1
LINK: link types - CORRECT ANSWER - LINK: point-to-point (PPP)
broadcast (shared wire)
LINK: MAC protocols - CORRECT ANSWER - LINK: channel partitioning, random
access, take turns
, LINK: channel partitioning - CORRECT ANSWER - LINK: divide channel into pieces to
allocate to node for exclusive use
TDMA (time division multiple access), access in rounds
FDMA (freq. division multiple access)
LINK: random access - CORRECT ANSWER - LINK: node transmit at full channel rate
no coordination among nodes
specify collision detection and recovery
LINK: random access protocols - CORRECT ANSWER - LINK: slotted ALOHA,
ALOHA, CSMA, CSMA/CD, CSMA/CA
LINK: slotted ALOHA - CORRECT ANSWER - LINK: Pros: node transmit at full rate,
decentralized, simple
Cons: collisions, wasteful, idle slots, clock sync
Node success = p(1-p)^N-1
Any node success = Np(1-p)^N-1
max efficiency = 37%
LINK: pure ALOHA - CORRECT ANSWER - LINK: no synchronization
collision probability increases (t0 collides with t0-1,t0+1)
Node success = p * (1-p)^2(N-1)
max efficiency = 18%
LINK: CSMA - CORRECT ANSWER - LINK: carrier sense multiple access
listen before transmitting for idle channel
collisions can still occur (determined by distance,propagation) wasting entire transmit time
Approach, CH5 UPDATED ACTUAL Exam
Questions and CORRECT Answers
LINK: link-layer implementation - CORRECT ANSWER - LINK: in every host in
network interface card
LINK: NIC - CORRECT ANSWER - LINK: network-interface card, has controller and
physical transmission
LINK: single bit parity - CORRECT ANSWER - LINK: detect single bit errors
LINK: 2D bit parity - CORRECT ANSWER - LINK: detect and correct single bit errors
LINK: error checking in link layer - CORRECT ANSWER - LINK: parity checking,
checksum, CRC
LINK: CRC - CORRECT ANSWER - LINK: cyclic redundancy check
D = data bits
G = generator
R = CRC code, remainder, length is G-1
LINK: link types - CORRECT ANSWER - LINK: point-to-point (PPP)
broadcast (shared wire)
LINK: MAC protocols - CORRECT ANSWER - LINK: channel partitioning, random
access, take turns
, LINK: channel partitioning - CORRECT ANSWER - LINK: divide channel into pieces to
allocate to node for exclusive use
TDMA (time division multiple access), access in rounds
FDMA (freq. division multiple access)
LINK: random access - CORRECT ANSWER - LINK: node transmit at full channel rate
no coordination among nodes
specify collision detection and recovery
LINK: random access protocols - CORRECT ANSWER - LINK: slotted ALOHA,
ALOHA, CSMA, CSMA/CD, CSMA/CA
LINK: slotted ALOHA - CORRECT ANSWER - LINK: Pros: node transmit at full rate,
decentralized, simple
Cons: collisions, wasteful, idle slots, clock sync
Node success = p(1-p)^N-1
Any node success = Np(1-p)^N-1
max efficiency = 37%
LINK: pure ALOHA - CORRECT ANSWER - LINK: no synchronization
collision probability increases (t0 collides with t0-1,t0+1)
Node success = p * (1-p)^2(N-1)
max efficiency = 18%
LINK: CSMA - CORRECT ANSWER - LINK: carrier sense multiple access
listen before transmitting for idle channel
collisions can still occur (determined by distance,propagation) wasting entire transmit time
