Data Communication and Networking – Metropolitan Area Networks (MAN) – IEEE 802.6 – DQDB (Distributed Queues, Dual Bus) MCQs

This set of Data communication and Networking Multiple Choice Questions and Answers (MCQs) focuses on “Metropolitan Area Networks MAN – IEEE 802.6 – DQDB (Distributed Queues, Dual Bus) ”.
 

1
. Each device in a DQDB system is connected _______.
  • to just one bus
  • to two buses
  • in a single ring structure
  • none of the above
2
. A DQDB device accesses a bus link through _______.
  • contention
  • token passing
  • distributed queues
  • CSMA/CD
3
. A DQDB device accesses a bus link through _______.
  • contention
  • token passing
  • distributed queues
  • CSMA/CD
4
. Each DQDB bus is _______.
  • unidirectional
  • bi-directional
  • connected to just the end stations
  • none of the above
5
. Traffic on a DQDB bus _______.
  • moves in both directions
  • alternates between buses
  • moves in one direction
  • none of the above
6
. If DQDB slots are generated on device X, then _______.
  • device X has no upstream stations
  • device X has no downstream stations
  • device X has no queues
  • device X can never transmit data
7
. If device Y is the end of a DQDB bus, then _______.
  • device Y has no upstream stations
  • device Y has no downstream stations
  • device Y has no queues
  • device Y can never transmit data
8
. If device X is neither the beginning nor the end of a DQDB bus, then _______.
  • device Z has no upstream stations
  • device Z has no downstream stations
  • device Z has no queues
  • none of the above
9
. In a DQDB with _______ devices, no queues are needed.
  • 2
  • 3
  • 4
  • any of the above
10
. If device X has 10 downstream stations and 3 upstream stations, how many stations are on the DQDB bus?
  • 10
  • 13
  • 14
  • 28
11
. To send data, a DQDB station needs to _______.
  • insert data into any empty slot
  • capture a token
  • make a reservation on the bus traveling in the upstream direction
  • make a reservation on the bus traveling in the downstream direction
12
. The DQDB _______ store requests for slots.
  • queues
  • switches
  • packets
  • reservations
13
. In a DQDB queue, slot requests are ordered according to _______.
  • station size
  • proximity to the slot-generating station
  • packet size
  • the time they were received
14
. When DQDB is implemented as a ring, _______ the slots.
  • one station generates
  • two stations generate
  • all stations generate
  • none of the above
15
. When DQDB is implemented as a ring and then a link or a station fails, _______ the slots
  • one station generates
  • two stations generate
  • all stations generate
  • none of the above
16
. The _______ layer in the DQDB protocol splits the data stream coming from the upper layer into 48-byte segments.
  • physical
  • data link
  • MAC
  • LLC
17
. Data from the LLC or upper layers are divided into _______-byte segments by the DQDB MAC layer.
  • 5
  • 48
  • 53
  • 64
18
. The DQDB MAC layer adds a _______ -byte header to each 48-byte segment
  • 5
  • 43
  • 58
  • 64
19
. The polynomial used for the DQDB CRC is x8 + x2 + x + 1. The divisor is therefore _______ bits
  • 7
  • 8
  • 9
  • 10
20
. The polynomial used for the DQDB CRC is x8 + x2 + x + 1. What is the divisor?
  • 100001011
  • 100000111
  • 101000101
  • 111000111
21
. The polynomial used for the DQDB CRC is x8 + x2 + x + 1. This means the CRC remainder is _______ bits in length.
  • 7
  • 8
  • 9
  • 10
22
. The DQDB header consists of _______ field(s).
  • one
  • two
  • four
  • five
23
. The _______ field controls access to the DQDB bus.
  • access
  • address
  • type
  • priority
24
. The DQDB _______ field holds a 20-bit VCI used in MAN and WAN transmissions
  • access
  • address
  • type
  • priority
25
. How many types of DQDB payloads are possible?
  • 1
  • 2
  • 3
  • 4
26
. How many DQDB priority types are possible?
  • 1
  • 2
  • 3
  • 4
27
. The DQDB _______ subfield indicates the occupancy status of the slot
  • busy (B)
  • slot type (ST)
  • reserved (R)
  • previous slot read (PSR)
28
. The DQDB _______ subfield defines the type of transmission (packet or isochronous).
  • busy (B)
  • slot type (ST)
  • reserved (R)
  • previous slot read (PSR)
29
. When the destination DQDB station has read the slot contents, it sets the _______ subfield to 0
  • busy (B)
  • slot type (ST)
  • reserved (R)
  • previous slot read (PSR)
30
. Which subfield in the access field is not currently in use by DQDB?
  • busy (B)
  • slot type (ST)
  • reserved (R)
  • previous slot read (PSR)
31
. A DQDB slot is the same size as a cell in _______.
  • B-ISDN
  • PPP
  • ISDN
  • ATM
32
. Which bit is set by a station to reserve a slot?
  • ST
  • PSR
  • RQ
  • B
33
. When a _______ uses DQDB, the address field is all 1s.
  • LAN
  • MAN
  • WAN
  • b and c

 
 
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