VoIP Midterm

Question 1

What is POTS?

Answer 1

Plain old telephone service/system (analog over copper loops)

Question 2

What is DTMF?

Answer 2

Dual-Tone Multi-Frequency (2 frequencies for one tone value)

Question 3

What is PSTN?

Answer 3

Public Switched Telephone Network (world’s circuit-switched telephone networks, using a reserved consistent path for signals allocated on call)

Question 4

What is ISDN?

Answer 4

Integrated Services Digital Network

Question 5

What makes up an ISDN?

Answer 5

Copper wires using TDM, virtual out of band control channel (D channel) and virtual data channels (B channels)

Question 6

What are the 2 varieties of ISDN?

Answer 6

Basic Rate (BRI) and Primary Rate (PRI)

Question 7

What does BRI consist of?

Answer 7

2 B channels (128kBps) and 1 D channel

Question 8

What does PRI consist of?

Answer 8

T1 and 23 B channels

Question 9

What is KTS?

Answer 9

Key Telephone System

Question 10

What is PBX?

Answer 10

Private Branch Exchange

Question 11

What are properties of KTS?

Answer 11

Hard wired, shared lines, for small business

Question 12

What are properties of PBX?

Answer 12

Line cards (LAN), trunk cards (WAN), control cards (routers/switches)

Question 13

What is VoIP?

Answer 13

Voice over IP, audio technology allowing voice communication to be encapsulated into binary packets for an IP network

Question 14

What is UC?

Answer 14

Unified Communications; a set of products and the ability to unify multiple modes of communication under a single network.

Question 15

What are the steps to Voice Encoding?

Answer 15

1. Sample the analog signal
2. Quantize the sample
3. Encode the digital signal
4. Compress the samples to reduce bandwidth

Question 16

What is the Nyquist Theorem?

Answer 16

Sampling rate has to be at least twice the maximum frequency. It determines the minimum sampling rate of analog signals.

Question 17

What is Quantization?

Answer 17

The representation of amplitudes by a certain value (step) where samples are rounded up/down to the closer step

Question 18

What is Quantization Noise?

Answer 18

The inexactness from quantization.

Question 19

What is the result of Linear Quantization?

Answer 19

Higher SNR on large signals is better quality, lower SNR on small signals is worse quality.

Question 20

What is Logarithmic Quantization?

Answer 20

The reduction in step size (higher granularity) at lower signals to provide uniform SNR for all signals.

Question 21

What is SNR?

Answer 21

Signal-to-noise ratio

Question 22

What is a DSP?

Answer 22

Digital Signal Processor, an ASIC used for telephony applications at voice endpoints and can also be used for audio conferencing and transcoding

Question 23

What is an ASIC?

Answer 23

An Application Specific Integrated Circuit

Question 24

What is RTP?

Answer 24

Real Time Protocol, built on UDP and offers all the functionality required by voice packets

Question 25

What is RTCP?

Answer 25

Real Time Transport Control Protocol, based on periodic transmissions of control packets

Question 26

How is voice encapsulated?

Answer 26

In small packets at high packet rates

Question 27

What does Cisco's UC strategy consist of?

Answer 27

On-premises call control and UC applications

Question 28

What is CME?

Answer 28

Cisco Unified Communications Manager Express; VoIP management application which runs on an Integrated Services Router's (ISR) Internetworking Operating System (IOS)

Question 29

What functions does CME provide?

Answer 29

Call processing, dial plan administration, phone feature administration, directory services, gateway features and modules

Question 30

What is CUCM?

Answer 30

Cisco Unified Communications Manager

Question 31

What are examples of Cisco soft clients?

Answer 31

Jabber and WebEx

Question 32

What features are required for IP telephony networks?

Answer 32

``` PoE CDP/LLDP/Voice VLAN DHCP server TFTP server NTP server ```

Question 33

What telephony protocols are used in VoIP communication?

Answer 33

Gatekeeper for call control, most common signaling is SIP, after setup uses RTP

Question 34

What is SIP?

Answer 34

Session Initiation Protocol; designed to create, modify, and terminate a session over IP

Question 35

What are the 6 core methods used by SIP?

Answer 35

``` INVITE BYE REGISTER CANCEL ACK OPTIONS ```

Question 36

What is the IP phone startup process?

Answer 36

1. Obtain PoE 2. Learns VLAN information from CDP/LLDP 3. Requests IP from DHCP server 4. Receives DHCP IP configuration 5. Downloads Device Configuration File 6. Registers with gatekeeper 7. Gatekeeper responds with SIP 200OK

Question 37

What are the 3 tasks to prepare CME to support Cisco IP phones?

Answer 37

1. Configure the ISR to act as a TFTP server 2. Initial CME configuration - ISR voice services 3. Configure and generate phone configuration files

Question 38

What are the 3 mandatory SIP configuration steps?

Answer 38

1. Configure SIP VoIP services on ISR 2. Configure the source IP 3. Configure the maximum number of endpoints and DNs allowed on the CME

Question 39

What is a Voice Register Pool?

Answer 39

CME endpoints (IP phone)

Question 40

What is a Directory Number (DN)?

Answer 40

The virtual phone line associated with the voice register pool

Question 41

What does the Restart command do?

Answer 41

Performs a quick reset and updates DNs, phone buttons, speed dials

Question 42

What does the Reset command do?

Answer 42

Performs a full boot and updates Date/Time, phone firmware, CUCME source IP, TFTP download path, voice mail access number in addition to restart info

Question 43

What are the features of CME?

Answer 43

Softkey speed dials Call forwarding Hunt groups Voice Hunt groups

Question 44

What is an outside line?

Answer 44

A direct connection to the telephone line outside of the building, aka POTS line. With all phones on-hook, voltage should measure around 48V DC. To ring, applies a 90VAC signal.

Question 45

What are the 3 types of Analog Voice Ports?

Answer 45

Supervisory signaling, Address signaling, Information signaling

Question 46

What is Supervisory signaling?

Answer 46

Loop-start or ground-start

Question 47

What is Address signaling?

Answer 47

Pulse or DTMF

Question 48

What is Information signaling?

Answer 48

Call progression tones

Question 49

What are the types of interfaces that Gateways use to connect to non-IP devices?

Answer 49

Analog phones, fax, non-IP PBX, PSTN switches (CO)

Question 50

What are examples of analog interfaces?

Answer 50

Foreign Exchange Station/Office (FXS/FXO)

Question 51

What are examples of digital interfaces?

Answer 51

T1 (CAS,CCS) and E1 (CAS,CCS)

Question 52

What are the 4 call types?

Answer 52

Local - doesn't traverse WAN/PSTN On-net - Between two phones on the same data network Off-net - When a user dials an access code to access the PSTN PLAR - automatic connection

Question 53

What is a call leg?

Answer 53

A logical connection between two routers or between a router and a telephony device (hop) which is router-centric (only worried about next hop)

Question 54

What is a Dial Peer?

Answer 54

An addressable call endpoint which establishes call legs to complete an end-to-end call

Question 55

What are the 2 types of dial peers?

Answer 55

POTS dial peers, VoIP dial peers

Question 56

What are POTS dial peers?

Answer 56

Traditional telephony network connection that match calls to voice ports.

Question 57

What are VoIP dial peers?

Answer 57

Packet switched network connection that match calls to session targets (IP address or DNS name).

Question 58

What happens when voice register dn is configured with a number (destination pattern)?

Answer 58

A voice dial-peer is automatically created.

Question 59

What type of dial-peer will strip any digits that match the destination pattern before routing a call?

Answer 59

POTS dial-peer