Telco Basics, Convergence, and Total Network Connectivity

Question 1

Goal of Security

Answer 1

Confidentiality
Integrity
Availability
(authentication)
(nonrepudiation)

Question 2

Tip and Ring

Answer 2

Old fashioned way of saying “plus” and “minus” or ground and positive in electrical circuits
Derive their names from the operator’s cordboard plug.
Today, tip refers to the first wire in a pair of phone wires, ring is the second wire. Together they constitute the circuit that carries speech or data.

Question 3

The Step-by-step (or Strowger, the name of the undertaker who invented the switch) switch

Answer 3

connects pairs of telephone wires by progressive step-by-step operation of a series of switches.
Replaced the manual switchboard

Question 4

Common Control

Answer 4

A method of switching in which the control equipment is responsible for routing calls through the network (as opposed to step device responsible only for the next step in the connection).

Depends on a crossing or intersection of two points to make a connection. The switching matrix, or crosspoint array, depends on energizing a vertical line and a horizontal line and the point where they intersect represents the connection made.

Question 5

ESS

Answer 5

Electronic Switching System

Question 6

ESS (Electronic Switching System)

Answer 6

Early electronic switches were still analog (the “reed switch”), now replaced with digital switches.
Use stored program control as the next step to common control. Systems are much more fault tolerant.
Tremendous increase in speed of switching with the new digital switches.

Question 7

PABX

Answer 7

Private Automatic Branch Exchange. Another name for PBX.

Question 8

PBX

Answer 8

Private Branch Exchange

Question 9

Private Branch Exchange

Answer 9

A privately owned (usually scaled-down) switching system for a company.

Question 10

Transmission Media

Answer 10

Conducted
Copper wire, coax, fiber optic
Radiated
Microwave, satellite

Question 11

PCM

Answer 11

Pulse Code Modulation (PCM) is the most common method of encoding an analog voice signal into a digital bit stream.

Question 12

Sampling –

Answer 12

records the voltage level in time intervals along an analog wave.

Question 13

Quantizing –

Answer 13

rounding to the nearest discrete value

Question 14

Encoding –

Answer 14

Converting the numeric amplitude voltage levels into binary 8-bit code

Question 15

Decoding –

Answer 15

Converting the 8-bit code into the voltage level

Question 16

Reconstruction –

Answer 16

reproduces the original analog wave from the voltage levels

Question 17

Filtering –

Answer 17

strips noise out.

Question 18

The process of combining many signals into one composite signal – thus several calls can be transmitted at once over a single line.

Answer 18

Multiplexing

Question 19

FDM

Answer 19

Frequency Division Multiplexing

- Limited to analog transmissions.

Question 20

TDM

Answer 20

Time Division Multiplexing

Question 21

STDM

Answer 21

Statistical Time division multiplexing

Question 22

Blue Boxes

Answer 22

Blue boxes are nothing more then a device to generate pairs of tones, and a single 2600 Hz tone.

Question 23

Benefits of Voice Over Network

Answer 23

You may save some money
You may achieve some benefits of managing a voice and data network as one network
If you have IP phones, moves, adds, and changes will be easier and cheaper
Added, and integrated, new services including
Integrated messaging
Bandwidth on demand
Voice emails

Question 24

Terminal

Answer 24

A terminal, or a client, is an endpoint where H.323 data streams and signaling originate and terminate. It may be a multimedia PC with a H.323 compliant stack or a standalone device such as a USB (universal serial bus) IP telephone. A terminal must support audio communication; video and data communication support is optional.

Question 25

Gateway

Answer 25

A gateway is an optional component in a H.323-enabled network. When communication is required between different networks a gateway is needed at the interface. It provides data format translation, control signaling translation, audio and video codec translation, and call setup and termination functionality on both sides of the network.

Question 26

H.323 Components

Answer 26

IP Telephony Architecture includes Terminal, Gatekeeper and Gateway. (Also Routers)

Question 27

Gatekeeper

Answer 27

A gatekeeper is a very useful, but optional, component of an H.323-enabled network. Gatekeepers are needed to ensure reliable, commercially feasible communications. When a gatekeeper exists all endpoints (terminals, gateways, and MCUs) must be registered with it.

Question 28

What services does a Gatekeeper provide?

Answer 28

Address translation
Admission and access control of endpoints
Bandwidth management
Routing capability

Question 29

MCU

Answer 29

A multipoint control unit (MCU) enables conferencing between three or more endpoints. Although the MCU is a separate logical unit it may be combined into a terminal, gateway, or gatekeeper. The MCU is an optional component of an H.323-enabled network.

The multipoint controller provides a centralized location for multipoint call setup. Call and control signaling are routed through the MC so that endpoints capabilities can be determined and communication parameters negotiated.

Question 30

H.225

Answer 30

Performs the signaling for call control

Uses H.245 to establish and terminate individual logical channels for communication

Question 31

Five Phases of Signaling Process

Answer 31

Call setup
Initial communications and capability exchange
Establishment of audiovisual communication
Call services
Call termination

Question 32

Why Converge?

Answer 32

Save Money
- Eliminate long distance toll charges
- Eliminate duplicate infrastructures
- Increased competition in the industry
Enhancement of current applications and development of new applications
Collaborative tools
The industry has been heading there for a while now anyway…

Question 33

Broadcast networks –

Answer 33

no intermediate switching nodes, each station communicates over a shared medium
Packet radio networks
Satellite networks
Local networks
E.g. bus or ring

Question 34

Basic premise is that an uninterrupted connection exists between the endpoints (Circuit Switching)

Answer 34

Constant bandwidth dedicated to this session
Resources for this session reserved for the entire duration of the call
Blocking is possible as a circuit may not be available
Initial connection requires considerable work but once established, minimal to maintain it
The PSTN is a circuit switched network

Question 35

Packet Switching

Answer 35

Bursty Traffic
In packet switched network, data is fragmented into discrete units (packets)
Each packet contains information about its source and destination
A complete message may consist of 1000’s of packets
Packets may actually take different routes and may arrive out of order, or not at all
Packet switched networks do not reserve bandwidth for each connection
Addressing is organizationally based

Question 36

Why are digital transmissions preferred over Analog?

Answer 36

Digital equipment cheaper to produce
Digital signals provide higher quality communication
Digital less susceptible to ‘noise’
Digital signals easy to compress to reduce required bandwidth

Question 37

ISDN

Answer 37

Integrated Services Digital Network - Based on idea that not everyone will talk at the same time on phone.

Question 38

CATV

Answer 38

Community Antenna Television (CATV)

Question 39

DSL

Answer 39

Digital Subscriber Lines

Question 40

ADSL

Answer 40

Asymmetric Digital Subscriber Lines takes advantage of the fact that the majority of traffic is downstream not upstream and provides greater downstream data rates.

Question 41

CTI

Answer 41

Computer Telephony Integration - The software and hardware elements that allow a computer to manage telephone calls and integrate additional features beyond those offered by the PBX

Question 42

PSTN

Answer 42

Public Switched Telephony Networks