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44 Cards in this Set

  • Front
  • Back
Define ALI
Automatic Location Identification

The ALI database contains the records that map telephone numbers to geographic locations.
Define ANI
Automatic Number Identification

ANI is the calling-party number that is included with each call to identify where it came from.
Define PSAP
Public Safety Answering Point

The PSAP is the answering point where an emergency call is terminated.
Define ERL
Emergency Response Location

ERL is the location from which an emergency call is placed.
Define ELIN
Emergency Location Identification Number
An ELIN is a NANP telephone number used for routing an emerg call to the appropriate PSAP
Define MSAG
Master Street Address Guide

MSAG is a database maintained by a government agency. Maps geographic locations to PSAP.
Define "Selective Router"
A selective Router is a dedicated 911 switch in the service provider network that routes 911 calls to the appropriate PSAP based on "calling" (ANI)number. Note: Normal call routing uses the "called" number.
Define CAMA
Centralized Automated Message Accounting
A CAMA is an analog trunk that connects a customer switch directly to a selective router. It carries 911 traffic only.
Define CER
Cisco Emergency Responder

CER is an app the automatically tracks and updates moves, add, changes,to equipment in real time to keep track of locations for 911 purposes.
G.711 codec uses what coding scheme? What is total bandwidth excluding overhead?
PCM (Pulse Code Modulation)
Bandwith of 64kbps
G.726 codes uses what coding scheme? What is total bandwidth excluding overhead?
ADPCM (Adaptive Pulse Code Modulation)
Bandwith varies with sample size uses 4,3 or 2 bits/sample. Therefore bandwidth is 32Kbps, 24kbps, or 16 kbps
G.728 codes uses what coding scheme? What is total bandwidth excluding overhead?
LDCELP (Low-Delay Code Excited Linear Prediction)
Bandwidth of 16kbps
G.729 and G.729A codes uses what coding scheme? What is total bandwidth excluding overhead?
CS-ACELP (Conjugate Structure Algebraic Code Excited Linear Prediction)
Bandwidth of 8kbps
G.723 and G.729A codes uses what coding scheme? What is total bandwidth excluding overhead?
MPMLQ (Multipulse Maximum Likelihood Quantization)
Bandwidth of 6.3Kbps or 5.3kbps
Cisco voice equipment encapsulates ___ worth of audio in each PDU by default regardless of the codec used
Cisco uses DSP's that output samples based on digitization of ___ of audio.
State the formula used to determine the number of bytes encapsulated in a PDU given the CODEC bandwidth and sample size.
Bytes_per_Sample = (Sample_Size * CODEC_Bandwidth) / 8

Ex: 160 bytes per PDU = (.020sec * 64000 bits per sec) / 8 bits per byte

(assuming G.711 codec)
VoIP alone without cRTP uses a ___ byte IP/UDP/RTP header
40 byte header
List the Layer 2 overhead for EthernetII
18 bytes of overhead: 6 bytes for source MAC, 6 bytes for destination MAC, 2 bytes for type, and 4 bytes for CRC
List the Layer 2 overhead for Multilink Point-to-Point Protocol (MLP)
6 bytes of overhead: 1 byte for flag, 1 byte for address, 2 bytes for control (or type), and 2 bytes for CRC
List the Layer 2 overhead for Frame Relay Forum Standard 12 (FRF.12)
6 bytes of overhead: 2 bytes for data-link connection identifier (DLCI) header, 2 bytes for FRF.12 header, and 2 bytes for CRC
Describe overhead associated with IPSec per packet
IPSec will typically add 50-57 bytes of overhead per packet
Describe overhead associated with Layer 2 Tunneling Protocol / Generic Router Encapsulation (L2TP/GRE) per packet
L2TP/GRE will add 24 bytes of overhead per packet
Describe overhead associated with Multi Link Protocol (MLP) per packer
MLP will add 6 bytes of overhead per packet
Describe overhead associated with MPLS per packet
MPLS will add a 4 byte label to every packet
cRTP changes 40 byte overhead of IP/UDP/RTP header down to what?
4 bytes if CRC is used.
2 bytes if no CRC
Give the formula to calculate total bandwidth per call
Total_Bandwidth = ([Layer_2_Overhead + IP_UDP_RTP Overhead + Sample_Size] / Sample_Size) * CODEC_Speed
Define VAD and give average bandwidth savings associated with using it
Voice Activity Detection. Save average of 35 percent bandwidth assuming english language and other factors.
True or False... VAD is enabled by default for all VoIP calls?
What does GOS(.01) mean?
GOS (.01) means that one call is blocked in 100 attempts.
Define GOS
Grade of Service is a unit that measures the chance that a call will be blocked. Usually defined with traffic is at it peak. (ie: busiest time of the day)
State the equation to calculate traffic flow
A=C*T (A is the offered traffic, C is the number of call originating in a 1 hour period, T is the average holding time of the call)
Define an "Erlang"
An Erlang is a nondimensional unit that defines the amount of traffic one truck can handle in one hour.
State other measurement units equivalent to 1 Erlang
1 Erlang = 60 call minutes = 3600 call seconds = 36 centum call seconds (CCS)
List two example to peer-to-peer signaling protocols
SIP and H.323
List two examples of signaling protocols with client/server architectures
MGCP and Megaco/H.248
True or False: Codecs only compress the voice stream
List the major VoIP protocols
H.323, MGCP, Megaco/H.248, SIP, RTP, RTCP
When a voice stream is assigned UDP port numbers, RTP is typicaly assigned an ____ port number and RTCP is assigned the next ___ port number. Each voice call has four ports assigned: RTP plus RTCP in the transmit direction and RTP plus RTCP in the recieve direction.
even, odd
State the command to enable cRTP compression on an interface.
ip rtp header-compression [passive]

Note: Command must be defined on both ends. Use "passive" option on one end only.
In a WAN Model with centralized call processing define the role of the "Central Gateway Controller" (Call Agent)
The call agent handles the switching logic and call control for all sites under the central controller.
Which codec is typically used on WAN links?
G.729 (8kbps)
List typical features of centralized call processing deployments
- MCGP or Megaco/H.248 for call control,
- Cisco Call Manager at central site for managing call control
- Centralized apps (voicemail, etc)
- Up to 30000 phones per cluster
- Call Admission Control (CAC) to limit calls per site
- SRST for remote branches
Although not typical you can build centralized deployements with SIP or H.323 networks using what?
This is done using back-to-back user agents (B2BUA) or gatekeeper-routed call signaling (GKRCS)