Transcript Telephony Ntwk v3 0 PowerPoint

Telephony
Networking
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Lesson 1:
Telephony Essentials
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Objectives
•
•
•
•
•
•
•
•
•
Describe the basic components of the telephone service
Describe industry standards and protocols
Identify the purpose and function of the central office
Identify ways to connect to the central office
Identify various types of trunks and signaling methods
Explain various digital signal hierarchy terms and issues
Discuss SONET and SDH
Describe the purpose of the primary reference source
Describe the functions and uses of various types of
telephone cable and wiring plans
• List the common call-processing steps
Telephony Basics
• Basic telephone service consists of:
– Public switched telephone network (PSTN) – a
system of interconnected lines and switches
– Plain old telephone service (POTS) – standard
telephony wires that carry analog data
• The last mile – the POTS portion of the PSTN that
connects to a home or business (usually 2.5 miles)
• The local loop – the tip and ring wire in the RJ-11
connector that provide a complete circuit to the
central office
• On-hook condition – the line is not busy and is
ready for a connection
• Off-hook condition – the line is busy
Telephony Basics
(cont'd)
• Phone company terminology:
– Local exchange carrier (LEC) – the local
telecommunications company
– Local access and transport area (LATA) – the
area serviced by a LEC
– Incumbent local exchange carrier (ILEC) – a
telco already in business before the
Telecommunications Act of 1996
– Competitive local exchange carrier (CLEC) – a
company that competes with LECs and ILECs
– Interexchange carrier (IXC) – a company that
carries long-distance calls between LECs in
different LATAs
Industry Standards and Protocols
• International Telecommunications Union (ITU) –
manages worldwide telephony and networking
standards
– ITU-T series – standards documents labeled
A through Z
– Radio Equipment and Telecommunications
Terminal Equipment directive – determines
standards for wireless devices in the United
Kingdom and Europe
• Internet Engineering Task Force (IETF) – publishes
Requests for Comments (RFCs) that provide
information about standardized Internet protocols
The Central Office
• Central office (CO) – switching location for local
and long-distance calls
• CO uses three types of switches:
– Class 3 (also known as an IXC, remote or longdistance switch)
– Class 4 (also known as a tandem switch)
– Class 5 (also known as an end-office switch)
• Pulse Code Modulation (PCM) – converts analog
voice data to digital format, then back to analog
• PCM uses two compression algorithms:
– Mu-Law (used only in North America and Japan)
– A-Law (the standard for all international circuits)
CO Connections
• Point of presence (POP) – an interexchange carrier
that connects long-distance services to a local
connection
• Foreign Exchange Service (FX) – provides
telephone services from a CO that is outside the
local calling area
• Private Branch Exchange (PBX) – enables an
organization to create in internal telephonenumbering system
• Centrex – enables an organization to provide a
pool of lines (alternative to PBX)
• Direct Inward Dialing (DID)/Direct Dialing Inward
(DDI) – enables multiple telephone numbers to be
used on a few lines
Trunks and Signaling
• Trunk – a direct communication line between two switching
systems; used to establish end-to-end communications
between customers
– Ear and mouth (E&M) trunks – carry voice and data on one
series of lines, and signaling on a separate set of lines
– Analog loop-start trunks – use two wires (the tip and the
ring) to act as conductors for the connection
– Ground-start trunk lines – require that both ends of a
connection detect ground before the tip and ring wires
can create a loop
– Digital trunk lines – signaling information and data are
sent digitally
• A and B bits – signaling bits that allow a line to
determine when connected systems check for dial tone
and whether a remote system is in an on-hook or
off-hook condition
Digital Trunks and
the Digital Signal Hierarchy
• Digital signal hierarchy (DSH) – provides a
standard for digital signal levels
• Use DSH to purchase the required amount of
network bandwidth to accommodate telephone and
network connections
• DSH levels are analogous to the T-carrier system
• Digital signals use frames to carry data and
addressing information:
– Super frame
– Extended super frame (the most common
standard)
SONET and SDH
• Synchronous Optical Network (SONET)
– High-speed, fiber optic networks organized in rings
• Synchronous Digital Hierarchy (SDH)
– Fiber ring networks used internationally
– Essentially the same as SONET
SONET and SDH
(cont'd)
The basic measure of SONET speed is the Synchronous
Transport Signal level 1 (STS-1) frame, which travels at
51.84 Mbps
SONET and SDH
(cont'd)
The basic unit for SDH is the Synchronous Transport
Module (STM)-1 frame, which travels at 155.52 Mbps
SONET and SDH
(cont'd)
Benefits of using SONET/SDH
• You can use multiplexors and routers to combine
different data lines and streams onto one line
• One heterogeneous network can communicate with
another distant heterogeneous network via one
fiber optic ring
The Primary Reference Source
• Primary reference source (PRS) – a network of hyperaccurate clocks used to precisely time digital connections
• PRS strata
– Stratum 1 – extremely accurate but very expensive
– Stratum 2 – used by long-distance providers
– Stratum 3 – used by the CO
– Stratum 4 – used by PBXs
• Timing types
– Asynchronous – no timing information is shared
– Synchronous – a common system clock is used for all
trunk lines and networks involved
– Plesiosynchronous – a number of PRS clocks are used for
all networks involved
Cabling and Wiring
• Service wire center – houses one or more local switching
systems
• Main distribution frame (MDF) – the main interface between
the telco's lines and all internal lines
• Patch panel – interconnects voice and data lines with RJ-11
and/or RJ-45 connectors
• Intermediate distribution frame (IDF) – connects the MDF and
a user's telephone handset
• Combined distribution frame (CDF) – same as MDF and IDF
but also houses connections from incoming lines and lines
from inside equipment
• Minimum point of entry (MPOE) – the point at which phone
lines first enter your facility
– Network interface device (NID) – terminates the
connections from the central office
– Load coil – device that improves voice transmission
– Bridge tap – cable used to extend the loop
Call-Processing Steps
• Placing a call
– Call setup – the connection is built between the local loop
and the CO
– Call connection maintenance – the connection is
established and maintained
– Call completion – breaking the connection
• Common analog transmission impairments
– Loss – parts of the transmission are dropped
– Echo – parts of the conversation are repeated
– Noise – unwanted energy that interferes with the signal
– Crosstalk – parts of another conversation are heard
• Echo cancellation in hybrid networks
– When two-wire and four-wire networks are connected, a
hybrid network is created, which can result in echo
– An echo canceller balances the ohm levels between the
lines, thereby eliminating the echo
Summary
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

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
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Describe the basic components of the telephone service
Describe industry standards and protocols
Identify the purpose and function of the central office
Identify ways to connect to the central office
Identify various types of trunks and signaling methods
Explain various digital signal hierarchy terms and issues
Discuss SONET and SDH
Describe the purpose of the primary reference source
Describe the functions and uses of various types of
telephone cable and wiring plans
 List the common call-processing steps
Lesson 2:
Investigating the Local Loop
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Objectives
• Explain the importance of a demarcation point in
telephony
• Identify signaling types used in the local loop
• Use numbering standards, including the North
American Numbering Plan (NANP) and United
Kingdom standards
• Explain how the local loop is wired
• Wire RJ-11 and RJ-12 connectors
• Wire BT-431A and BT-631A connectors
• Wire a wall jack and a line jack unit
Inside the Demarcation Point
• Minimum point of entry (MPOE)
– The telco's demarcation point
– The point where telco equipment ends and
inside local loop wiring begins
• Drop wire – the line from the telephone pole to the
MPOE
• Station wire – the line inside the MPOE
Getting to the Local Loop
• Global numbering plans
– ITU Recommendation E.164 establishes
standards for numbering plans
– Telephone numbers should not exceed 15
characters
• North American Numbering Plan (NANP)
– Numbers are 10 digits long
Getting to the Local Loop
(cont'd)
• Area code jeopardy and relief
– Realignment – move areas from one area code
to another
– Split – create a new area code
– Three-way split – create two new area codes out
of one area code
– Overlay – assign a new area code in the same
geographic area as an existing area code
• Specified Numbering Scheme (SNS)
– Enables people in the U.K. to make calls using a
uniform formula
Signaling Types
• Three types of signaling:
– Rotary/pulse or multi-frequency (MF) – used on
rotary dial phones
– Dual tone multi-frequency (DTMF) – generated
by touch-tone pads on all standard phones
– Digital – does not process audible tones
RJ-11 Connectors and Wiring
RJ-11 Connectors and Wiring
(cont'd)
• Telephone jacks constitute a tip and ring
• Tip
– The "transmit" wire
– The positive side of the circuit (in relation to the
ring)
• Ring
– The "receiving" wire
– The negative side of the circuit (in relation to the
tip)
RJ-12 Modular Connector
RJ-11 Wall Connector Wiring
BT-431A Connectors
BT-631A Connectors
Line Jack Units
• Three types of line jack units
– Master
– PBX master
– Secondary
• Master line jack units contain:
– A 26-amp surge protector
– A 1.8 uf, 250-volt capacitor
– A 470-ohm service resistor
– Six terminals designed to accept wiring from the
wall
Wall Jack Wiring Diagram
Summary
 Explain the importance of a demarcation point in
telephony
 Identify signaling types used in the local loop
 Use numbering standards, including the North
American Numbering Plan (NANP) and United
Kingdom standards
 Explain how the local loop is wired
 Wire RJ-11 and RJ-12 connectors
 Wire BT-431A and BT-631A connectors
 Wire a wall jack and a line jack unit
Lesson 3:
Infrastructure Issues and Standards
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Objectives
• List common telephony connectivity and safety
issues
• Identify safety procedures
• Explain safety standards
• Determine the proper cabling procedures for
specific environments
• Identify various cable terminations
• Wire an RJ-45 connector
• Explain the importance of plenum cabling
• Explain the necessity of securing equipment
Common Telephony Issues
• Quality assurance and business continuity
– Uptime – the length of time a device has remained
operational
– Mean time between failure (MTBF) – the predicted amount
of time a device will function before it requires
maintenance or replacement
– Return on investment (ROI) – the calculations made to
ensure that equipment will result in company profitability
• Telecommunications reliability and safety issues:
– Extreme temperatures
– Vibration and shock
– Humidity
– Fire
– Noise
– Altitude
Common Telephony Issues
(cont'd)
• Electromagnetic compatibility
– Electrostatic discharge (ESD) – An uncontrolled buildup of
electrical current
– Radio frequency interference (RFI) – A signal that causes
another device to operate improperly
– Electromagnetic interference (EMI) – interference
produced by electromechanical devices
• Solutions for electrical issues:
– EMI suppression filters
– Capacitors
– Inductors
– Line filters
– Shielding
– Ensuring proper humidity
• Personnel safety concerns and procedures
Network Equipment Building System
• Network Equipment Building System (NEBS)
– Protects people and property
– Ensures operational continuity in the telephony industry
• NEBS sets standards for the operation of telephony
equipment with respect to:
– Earthquake zones
– Operating conditions and transport conditions
– Levels of contaminants
• NEBS standards documents
– GR-63-CORE (Physical Protection)
– GR-1089-CORE (Electromagnetic Compatibility and
Electrical Safety)
Standards Bodies
Standards bodies provide telephony standards
– Independent Committee for the Supervision of
Standards of Telephone Information Services
(ICSTIS)
– International Organization for Standardization
(ISO)
– Independent Testing Laboratory (ITL)
– European Telecommunications Standards
Institute (ETSI)
– Federal Communications Commission (FCC)
– Telecommunications Industry Association (TIA)
– Electronic Industries Alliance (EIA)
– British Standards Institute (BSI)
Proper Cabling Procedures
When pulling cable:
– Avoid sharp bends in the cable
– Take care to eliminate sharp edges in conduits
and other areas where cable might get worn or
cut
– Make sure that wiring does not interfere with
mechanical equipment
– Avoid passing wire close to fluorescent lights
– Ensure that you are using the right type of cable
for a particular job
Choosing the Proper Cable
• American Wire Gauge (AWG) standard
• Standard gauges
– 22 AWG – floor or wall cable
– 24 AWG – backbone and drop cable
– 26 AWG – drop cable and devices that pass data
between similar devices (daisy chaining)
• The EIA/TIA 568 standard is the most commonly
used for twisted pair cabling
IBM Cabling Standard
RJ-45 connector – an
eight-pin modular
cable ending used in
Ethernet networks
12345678
Crossover cabling –
allows two systems
to communicate
without the use of an
intermediary device,
such as an Ethernet
hub
WO O WG Be WBe G WBr Br
Serial Cable Termination
• Data terminating equipment (DTE) – a serial device
that transmits and receives data digitally
• Data communications equipment (DCE) – a device
that is attached to a communications line and is
capable of altering a signal in transit
• RS-232 – a standard that enables DTE and DCE
devices to communicate
• Universal Asynchronous Receiver-Transmitter
(UART) – translates parallel communication into
serial
• Additional ITU communication standards
– V.24 through V.90
PVC vs. Plenum Cabling
• Plenum – the space above a dropped ceiling or
behind a wall
• UTP or STP cables have a polyvinyl chloride (PVC)
jacket (emits toxic gas when burned)
• When installing cable in a plenum:
– Encase UTP or STP cable in a protective metal
conduit
– Use plenum cabling (has a Teflon jacket that
inhibits burning)
Securing Equipment
• Physically secure telephony equipment using
brackets
• Isolate power sources by grounding them properly
– PBX grounding: a steel rod 6 feet (2 meters)
underground to which you attach the PBX
ground lead
Summary
 List common telephony connectivity and safety
issues
 Identify safety procedures
 Explain safety standards
 Determine the proper cabling procedures for
specific environments
 Identify various cable terminations
 Wire an RJ-45 connector
 Explain the importance of plenum cabling
 Explain the necessity of securing equipment
Lesson 4:
Troubleshooting
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Objectives
•
•
•
•
•
•
•
•
Identify common troubleshooting tools
Use a line test handset (butt set)
Use a tone and probe kit
Use a digital multimeter
Use a line tester
Discuss how to troubleshoot analog lines
Discuss how to troubleshoot digital lines
Discuss telephony power issues
Troubleshooting Terms
•
•
•
•
•
Short (continuity)
Open (open fault)
Terminator
Cross
Polarity
•
•
•
•
Split
Line imbalance
Loopback testing
End-to-end testing
Troubleshooting Tools
• Telephone line test set
– Also called a butt set or handset
– Used to test line quality
– Used to check line polarity
– Used to determine loss of current
• End-to-end and loopback testing
– A butt set is used to generate tones and
frequencies to test lines
• Can use analog butt sets to listen to digital
communications by going into "data safe mode"
Troubleshooting Tools
(cont'd)
• Tone and probe kit
– A tone generator emits tones across a wire
– A probe listens on the other end of the wire for tones
emitted by the tone generator
• Uses
– Identify open circuits
– Locate short circuits
– Identify breaks in a cable
– Test polarity of a line
– Determine line voltage
– Identify lines that are causing crosstalk
– Find a single conducting wire in a bundle of wires
– Provide talk battery power to test a line with no dial tone
Troubleshooting Tools
(cont'd)
• Multimeter
– Measures resistance, current and voltage in an
electrical circuit
Troubleshooting Tools
(cont'd)
• Punchdown tool
– Inserts wires in 66 and 110 punchdown blocks
• Line tester
– Determines if a short exists in a line
• Laptop computer
– Connects to a telephony network and uses
packet sniffers to troubleshoot lines
• Additional devices
– ABS
– DTMF decoder
– Acoustic coupler
– Modular breakout adapter
Troubleshooting Analog Lines
• PBX and ground-start analog lines
– At the PBX, use a butt set to isolate crosstalk to
determine if the problem is within or outside the
building
• Securing connections with a punchdown tool
– Poorly closed connections or improperly set
lines can cause line noise
• Checking for line noise
– Use a digital multimeter to measure for AC
voltage
– AC voltage > 1 volt = improper grounding
Troubleshooting Digital Lines
• Improper clocking configuration
– Voice and data lines must be precisely
synchronized using the CO's PRS
– Use a butt set to check for improper clocking
• Check the Service Profile Identifier (SPID)
– No connection will occur if the SPID is missing
or incorrect
– SPID = area code + 7-digit phone number +
ISDN number
• Check for proper termination
• Be aware of different ISDN voice-encoding
standards
Troubleshooting Digital Lines
• Consider signal-to-noise ratio
• Test equipment for digital networks
– Signal/spectrum analyzer
– Multimeter
– Oscilloscope
– Network analyzers
– Time domain reflectometer (TDR)
– Service-specific test set
(cont'd)
Telephony Power Issues
• Grounding/earthing
– When connecting telephony and LAN-based equipment,
ensure that all systems have only one ground path
– Use an earth loop tester to avoid grounding problems
– Ensure that power is connected properly at the electrical
termination device (circuit breaker)
• Physical security
– Place all equipment in a dedicated server or CTI room
• Telephones and ring voltage
– REN value determines the ringing voltage
– -90 v AC charge needed to ring a standard analog
telephone
Summary



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Identify common troubleshooting tools
Use a line test handset (butt set)
Use a tone and probe kit
Use a digital multimeter
Use a line tester
Discuss how to troubleshoot analog lines
Discuss how to troubleshoot digital lines
Discuss telephony power issues
Lesson 5:
Analog and Digital Signaling
Copyright © 2006 Prosoft Learning, a VCampus Company - All rights reserved.
Objectives
• Describe signaling categories and audible
progress tones
• Compare and contrast in-band and out-of-band
signaling
• Describe analog signaling in regard to E&M,
loop-start and ground-start trunks
• Describe digital signaling, including T1 and ISDN
lines
• Describe the nature and functions of Private
Integrated Services Networks (PISNs)
• Discuss Signaling System Seven (SS7)
• Describe Computer-Telephone Integration
Signaling Categories
• Signaling categories:
– Supervision – detects changes to a particular
line
– Addressing – responsible for routing signals to
the correct switch
– Alerting – audible alert signals
– Call progress – signals that maintain calls
• Audible call progress tones:
– Dial tone
– Busy signal
– Receiver off hook too long
– Nonexistent number
In-Band and
Out-of-Band Signaling
• In-band signaling
– The process of allowing the control signal to
share the same path as the voice and data
• Out-of-band signaling
– The process of using a separate channel for
signaling purposes
Analog Signaling
• Ear and mouth (E&M) signaling
– Separate signaling wires for voice and data
Analog Signaling
(cont'd)
• Grounding on E&M lines
– Immediate start
– Wink start
– Delay-dial start
• Reducing E&M trunk glare with wink starting
Loop-Start Analog Trunk Signaling
Ground-Start Analog Trunk Signaling
(Idle and Outgoing Calls)
Ground-Start Analog Trunk Signaling
(Incoming Calls)
Digital Signaling
• T1 lines and in-band signaling
– Channelized T1 – 24 channels of 56 Kbps for
voice and data
– Unchannelized T1 – 1.536 Mbps for voice and
data
• Bit robbing
– The practice of using the least significant
portions, or bits, of a data or voice channel for
signaling
– The T1 Superframe (SF) robs the A and B bits for
signaling
– The Extended Superframe (ESF) has four bits (A,
B, C and D), though only A and B are used
Digital E&M Signaling
A and B bit settings
for sending and
receiving switches:
– Idle – A and B bits
are set to 0 for
both switches
– Call initiation –
switch A sets bits
A and B to 1;
switch B sets bits
A and B to 0
– Call completion –
both switches
have the A and B
bits set to 1
Digital Ground and Loop Starts
• When an FXS is idle:
– The CO's A and B bits = 1
– The PBX's A bit = 0; the B bit = 1
• When a digital loop-start line is in an idle state:
– The A bits for the CO/FXO and PBX/FXS = 0
– The B bits for the CO/FXO and PBX/FXS = 1
• When an FXS or PBX makes an outgoing call:
– The CO/FXO's A bit = 0; the B bit = 1
– The PBX/FXS's A bit = 1; the B bit = 1
Integrated Services Digital Network
(ISDN)
• ISDN can carry voice, FAX, imaging or data
communications
• Two types of ISDN:
– ISDN Basic Rate Interface (BRI) – Two 64-Kbps
channels for voice or data; one 16-Kbps channel
for signaling
– ISDN Primary Rate Interface (PRI) – 23 64-Kbps
channels for voice or data; one 16-Kbps channel
for signaling
• B channel (bearer channel) – carries voice or data
• D channel (delta channel) – carries signaling
• H channel – combined B channels
ISDN Protocols
• I.430 – explains how the ISDN interface uses the
physical and data link layers of the OSI/RM (Layers
1 and 2, respectively)
• ISDN interfaces must use reference points between
the telco and the end station:
– U interface
– S interface
– T interface
– Network Termination Equipment (NTE)
– Terminal adapter
– Terminal equipment
ISDN Protocols
(cont'd)
• High Level Data Link Control – Link Access
Protocol D Channel (HDLC – LAPD)
– Used in ISDN connections to provide signaling
– LAPD operates solely in the D channel of an
ISDN line
– LAPD provides flow control and data reliability
• Q.931 and Q.932
– Q.931 manages how a session is begun and
ended
– Q.932 makes it possible to modify connections
that are already under way
Private Integrated
Services Network (PISN)
PISN, showing connections via two different PINX types
Private Integrated
Services Network (PISN)
(cont'd)
•
A PISN consists of the following:
– End nodes – provide specific services, including voice and data
– Transit (transport) nodes – provide routing services to ensure
that calls and network requests arrive at the proper destination
PISN Signaling Methods
• Digital Private Network Signaling Scheme (DPNSS) – a
collection of protocols that enable PBX-to-PBX
communication over ISDN lines
• Tromboning – a problem that occurs when a second
connection is opened unnecessarily to accommodate a call
that is being re-transferred back from one PINX to another
• QSIG – the de facto standard for PISNs connected by PINX
equipment through ISDN lines
– QSIG basic services – enable PISN elements to establish
voice and data calls
– QSIG supplementary services – help control remote PINXs
built by different manufacturers
– Additional network features (ANF) – signaling
enhancements that help handle calls
PISN Signaling Methods
• QSIG basic call (QSIG BC)
(cont'd)
Q and C Reference Points
• Q reference point – the point at which a logical
PINX interface communicates with a remote PINX
• C reference point – the physical interface between
a PINX and a trunk line
Signaling System Seven (SS7)
• Signaling System Seven (SS7) – a packet-switched network
protocol used by telcos in calls that pass between switches
• High Level Data Link Control (HDLC) – a protocol that divides
signaling data into discrete packets
– HDLC allows three categories of stations (entities) to
communicate:
• Primary – initiates and controls communication
• Secondary – responds to communication
• Combined – controls and responds to communication
HDLC frame
Signaling System Seven (SS7)
(cont'd)
• SS7 elements:
– Service Switching Point (SSP)
– Signaling Transfer Point (STP)
– Service Control Point (SCP)
• SS7 message types:
– Initial Address Message (IAM)
– Address Complete Message (ACM)
– Answer Message (AM or ANM)
– Release Message (REL)
– Release Complete (RLC)
Computer-Telephone
Integration (CTI)
CTI – the ability
for telephony
networks and
data networks
to share data
Summary
 Describe signaling categories and audible
progress tones
 Compare and contrast in-band and out-of-band
signaling
 Describe analog signaling in regard to E&M,
loop-start and ground-start trunks
 Describe digital signaling, including T1 and ISDN
lines
 Describe the nature and functions of Private
Integrated Services Networks (PISNs)
 Discuss Signaling System Seven (SS7)
 Describe Computer-Telephone Integration
Telephony Networking





Telephony Essentials
Investigating the Local Loop
Infrastructure Issues and Standards
Troubleshooting
Analog and Digital Signaling