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CTY L6 Review > VoIP Final > Flashcards

VoIP Final Flashcards

1
Q

IP guarantees reliability, flow control, and error detection/correction (T/F)

A

False

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2
Q

TCP overhead for reliability is large and consumes bandwidth (T/F)

A

True

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3
Q

UDP offers reliability (T/F)

A

False

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4
Q

RTP makes it possible to identify type of information carried, add markers/sequence numbers, and monitor packets (T/F)

A

True

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5
Q

RTCP makes it possible to convey packet count/delay/loss and jitter (T/F)

A

True

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6
Q

RTP Header size?

A

12 bytes

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7
Q

UDP Header size?

A

8 bytes

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8
Q

IP Header size?

A

20 bytes

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9
Q

Frame Header size?

A

18 bytes

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10
Q

By default, 20ms of voice is packetized into a single IP packet (T/F)

A

True

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11
Q

G.729 Payload size?

A

20 bytes (1/2 the headers)

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12
Q

G.711 Payload size?

A

160 bytes (4x the headers)

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13
Q

What is the order of CUC integration using SIP?

A

Voicemail profile -> Voicemail pilot -> Route pattern -> SIP trunk

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14
Q

What are the two basic call types for CUCM routes?

A

On-Net Calls - Destination DN is registered with CUCM

Off-Net Calls - External Route Patterns must be configured on CUCM

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15
Q

CUCM is more complex than CME because it is a distributed scalable system (T/F)

A

True

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16
Q

CUCM is not intended for large-enterprise environments (T/F)

A

False

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17
Q

What are the elements of a CUCM Dial-Plan?

A

Route Patterns - match a string of dialed digits
Route Lists - ordered list of route groups
Route Groups - list of devices configured to support circuits to the PSTN
Gateways / Trunks

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18
Q

What is MGCP?

A

Media Gateway Control Protocol, for controlling media gateways on IP networks connected to the PSTN

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19
Q

What are the components of MGCP?

A

Gatekeeper (Call agent)

Gateway (Connects POTS phones or PSTN-b-channels to an IP network)

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20
Q

What are the 4 ways to add phones in CUCM?

A

Manual configuration
Auto-registration
Bulk Administration Tool (BAT)
Auto Register Phone Tool (TAPS)

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21
Q

What are the special functions and services used by IP phones?

A

NTP, CDP/LLDP, PoE, DHCP, TFTP, DNS

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22
Q

What are the minimal tasks for preparing CUCM?

A
  1. Configure and verify network services
  2. Configure enterprise parameters
  3. Configure service parameters
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23
Q

What tools need to be activated for CU serviceability?

A

CallManager
DHCP Monitor Service
TFTP

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24
Q

What is the CUCM Serviceability Interface?

A

Web-based troubleshooting tool. The Tools menu allows to stop, start or restart services.

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25
Q

The CUCM Administration Interface is where most telephony management is done (T/F)

A

True

26
Q

The CUCM OS Administration Interface allows an administrator to monitor and interact with the Linux-based operating system (T/F)

A

True

27
Q

What does the command “priority bandwidth” do?

A

Allocates a fixed bandwidth to a class and ensures fast forwarding. Traffic which exceeds it is dropped if congestion exists.

28
Q

What does the command “priority percent percentage” do?

A

Allocates a percentage of configured/default bandwidth to a class and ensures fast forwarding. Traffic which exceeds it is dropped if congestion exists.

29
Q

What does a policy map do?

A

Defines a traffic policy which configures the QoS features associated with a traffic class previously identified.

30
Q

What are the 3 major elements of a traffic policy?

A
  1. Case sensitive name
  2. Traffic class (class-map reference)
  3. QoS policy associated with the traffic class
31
Q

What are the 3 major elements of a traffic class?

A
  1. Case sensitive name
  2. Match commands
  3. Instructions on evaluating match commands
32
Q

What are the 2 modes class maps operate in?

A 
Match all (default): all conditions have to succeed
Match any: at least one condition must succeed
33
Q

What are the 3 steps for defining an overall QoS policy?

A
  1. Define classes (class map)
  2. Define QoS policies for classes (policy map)
  3. Apply a service policy
34
Q

What is the MQC CLI?

A

Modular Quality of Service CLI. Allows you to define a traffic class, create policy, and attach the policy to an interface.

35
Q

For scalability, classification should be enabled as close to the edge as possible, depending on device capabilities (T/F)

A

True

36
Q

What is NBAR2?

A

Network-Based Application Recognition. An intelligent classification engine that classifies applications and discovers what traffic is running on the network.

37
Q

What does NBAR2 provide?

A

Bidirectional, per-interface and per-protocol statistics

38
Q

What is sub-port c;assification?

A

NBAR’s method of classifying application traffic by looking into the TCP/UDP payload itself and classify based on content.

39
Q

NBAR requires CEF to be enabled before protocol discovery (T/F)

A

True

40
Q

NBAR2 HTTP-Based Visibility Dashboard provides a web interface displaying network data and related information (T/F)

A

True

41
Q

What is a protocol pack?

A

A set of protocols developed and packaged together.

42
Q

What are the benefits of WFQ?

A

Simple configuration
Guarantees some throughput to all flows
Drops packets of most aggressive flows

43
Q

What are the drawbacks of WFQ?

A

Possibility of multiple flows ending up in one queue
Lack of control over classification
Cannot provide fixed bandwidth guarantees

44
Q

What is CBWFQ?

A

Class-based Weighted Fair Queuing. A mechanism used to guarantee bandwidth to classes and extends WFQ functionality.

45
Q

CBWFQ guarantees bandwidth according to weights assigned to classes (T/F)

A

True

46
Q

CBWFQ weights are calculated from bandwidth or a percentage (T/F)

A

True

47
Q

What are the ways bandwidth can be defined?

A

Bandwidth (kbps)
Percentage of bandwidth (% of available interface bandwidth)
Percentage of remaining available bandwidth

48
Q

One service policy can have mixed types of weights (T/F)

A

False

49
Q

What are the benefits of CBWFQ?

A

Custom-defined classifications
Minimum bandwidth allocation
Finer granularity and scalability

50
Q

What are the drawbacks of CBWFQ?

A

Voice traffic can still suffer unacceptable delay (no priority)

51
Q

What is LLQ?

A

Low latency queuing. Combines priority queuing and CBWFQ to create more versatile queuing mechanisms.

52
Q

Long transmit queue

A

May result in poor performance of the software queuing system

53
Q

Short transmit queue

A

May result in a large number of interrupts which causes high CPU utilization and low link utilization

54
Q

What are the 3 QoS models?

A 
Best effort (default)
Integrated Services (IntServ)
Differentiated Services (DiffServ)
55
Q

What is DSCP?

A

Differentiated Services Code Points

56
Q

What is a QoS service class?

A

A logical grouping of packets that are to receive a similar level of applied quality

57
Q

What is FIFO?

A

First-In, First-Out Queuing. Involves storing packets when the network is congested and forwarding in order of arrival when no longer congested.

58
Q

What is PQ?

A

Priority Queuing. Puts data into four levels of queues: high, medium, normal (default) and low.

59
Q

What is CQ?

A

Custom queuing. Handles traffic by assigning a specified queue space to each packet class and servicing up to 17 queues in round-robin.

60
Q

What is WRED?

A

Weighted Random Early Detection. Provides a method that stochastically discards packets if increased congestion.

CTY L6 Review (4 decks)

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