Telephony Networking Slideshow

Telephony Networking

Lesson 1: Telephony Essentials

Objectives • Define codec, and describe the G.711 protocol • Define Pulse Code Modulation (PCM), and distinguish between the μ-Law and A-Law companding algorithms • Explain common feature sets for voice calls, including call waiting, call blocking, call forwarding, call monitoring, callback, and additional private network features • Explain Direct Inward Dialing (DID) • Define hunt groups • Identify elements of a call center or contact center, including call routing, caller ID, automatic call distributors, pop-ups, instant messaging/chat, e-mail, real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

Telephony Networking

Objectives (cont’d) • Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface • Identify symptoms of improper clocking configuration (e.g., problems with synchronization) • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-ofband signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wire-to-four-wire hybrids)

Telephony Networking

Analog to Digital 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) • G.711 – international standard for encoding voice on a 64-Kbps channel

Telephony Networking

CO Connections • Point of presence (POP) – an interexchange carrier that connects long-distance services to a local connection • Private Branch Exchange (PBX) – enables an organization to create an internal telephonenumbering system • Direct Inward Dialing (DID) / Direct Dialing Inward (DDI) – enables multiple telephone numbers to be used on a few lines

Telephony Networking

Common Voice Call Features • Call waiting – suspends current call to pick up another incoming call • Call blocking – prevents calls from ringing through based on point of origination; also, restricting a station from making outbound or long-distance calls • Call forwarding – redirects calls from one phone number to a second phone number • Callback – monitors a busy phone and completes a call to that number when the busy phone goes back on-hook

Telephony Networking

Additional Private Features • Call monitoring – keeps detailed records of phone transactions • Traffic reporting – reports that detail usage on incoming and outgoing trunk groups • Ringing preferences – programs certain lines to ring only on particular stations • Automated attendant – answers call, collects station number of desired party, then transfers the call • Voice mail systems – integrated voice mail • Outward restrictions – restricts stations to making only intercom or local calls • Private numbering plans – allow users to call internal extensions without using an outside line • Unified messaging – stores all forms of messaging, e-mail, voice mail and fax, in a centralized server

Telephony Networking

Hunt Groups • Allow incoming calls to be routed to available alternate numbers – Most-idle line hunting – used to distribute the load over all trunks – Sequential hunting – hunts in a sequence from the dialed number through to the end of the hunt group – Circular hunting – hunts all lines in the hunt group before returning a busy signal

Telephony Networking

Call / Contact Centers • Centralized office used for processing a large volume of calls • Companies use call centers to interact with their customers • Calls are automatically distributed among agents • Predictive dialers automatically dial batches of phone numbers for connection to agents • Calls are recorded for quality assurance and legal purposes • Contact centers allow for interaction with agents via phone, e-mail, chat or instant messaging, and Web (click-to-talk) Telephony Networking

Call / Contact Center Software • Automatic call distribution (ACD) – used to distribute the load over all trunks • Interactive voice response (IVR) – allows a caller to interact with a database

• Customer relationship management (CRM) – integrates with ACD software, allowing the software to query the database and display customer information on an agent’s screen • Metrics – enable supervisors to analyze performance Telephony Networking

Elements of Computer-Telephony Integration (CTI) • • • • • • • • • • • • •

Calling line information display Authentication of callers Interactive voice response to callers Live voice or touchtone input On-screen pop-ups On-screen dialing and phone control Receiving and routing fax messages Logging on Agent instruction State control Multi-channel blending Managing voice or video conferences Call routing and reporting Telephony Networking

Hosted Solution Benefits • Relatively short and simple start-up cycles • Eliminates the need for specialized staff • Tech support and maintenance handled by hosting company • Allows for maximum flexibility in agent placement and routing of incoming calls to agents • Enables a “virtual call center” Telephony Networking

Trunks and Signaling • Analog loop-start trunks used in most standard home phones • Ground-start trunk lines often used to connect a PBX to a CO

Telephony Networking

The Primary Reference Source • Primary reference source (PRS) – a hierarchical system wherein a super-accurate time source is defined as stratum-0; used to time and synchronize digital connections • PRS strata – Stratum 1 – extremely accurate; usually provided by a GPS-enabled device – Stratum 2 – at one time used by longdistance providers, but now largely out of use – Stratum 3/3E – used by local switches, gatekeepers and gateways – Stratum 4 – used by PBXs and telco channel banks Telephony Networking

PRS (cont’d) • 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 • Symptoms of improper clocking – Audible pops and clicks – Loss of data Telephony Networking

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

Telephony Networking

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 Telephony Networking

Summary  Define codec, and describe the G.711 protocol  Define Pulse Code Modulation (PCM), and distinguish between the μ-Law and A-Law companding algorithms  Explain common feature sets for voice calls, including call waiting, call blocking, call forwarding, call monitoring, callback, and additional private network features  Explain Direct Inward Dialing (DID)  Define hunt groups  Identify elements of a call center or contact center, including call routing, caller ID, automatic call distributors, pop-ups, instant messaging/chat, e-mail, real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

Telephony Networking

Summary (cont’d)  Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface  Identify symptoms of improper clocking configuration (e.g., problems with synchronization)  Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wireto-four-wire hybrids)

Telephony Networking

Lesson 2: Boundaries, Numbers, Wiring and Safety

Objectives • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analog and/or digital butt set, volt meter, time domain reflectometer) • Identify safety procedures for working with convergent network equipment (e.g., power, proper grounding, electrostatic discharge [ESD], radio frequency interference [RFI], electromagnetic interference [EMI])

Telephony Networking

Demarcation Point • Demarcation point (“demarc”) – The point at which the telco’s network ends and connects with the wiring of the customer premises – Operational control or ownership of services changes here • Minimum point of entry (MPOE) – the point where telco equipment ends and inside local-loop wiring begins

Telephony Networking

Telephone Numbers • Global numbering plans – ITU Recommendation E.164 establishes standards for numbering plans – Telephone numbers should not exceed 15 characters • National numbering plans – Define the numbering structure for a specific country or group of countries • Regional numbering plans – Define the numbering structure for a specific geographic region • Private numbering plans – Allow companies to create their own numbering systems Telephony Networking

Signaling Types • Three types of signaling: – Rotary / pulse or multifrequency (MF) – used on rotary dial phones

– Dual-Tone Multifrequency (DTMF) – generated by touch-tone pads on all standard phones – Digital – does not process audible tones

Telephony Networking

RJ-11 Connectors and Wiring

Telephony Networking

RJ-12 Modular Connector

Telephony Networking

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 – Mean time to repair (MTTR) – the time it will take to discover the failure and repair or restore service – Availability – the length of time a device or system is able to provide service • Availability = MTBF / MTBF + MTTR – Return on investment (ROI) – the calculations made to ensure that equipment will result in company profitability Telephony Networking

Common Telephony Issues (cont’d) Telecommunications reliability issues: – Extreme temperatures – Lightning – Power requirements and heat – Electrical safety – Vibration and shock – Earthquake – Humidity – Contaminants – Fire – EMI immunity – Noise – Altitude Telephony Networking

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 – Shielding – Ensuring proper humidity Telephony Networking

Common Telephony Issues (cont’d) • Personnel safety concerns and procedures – Tools – Loose clothing – Metal – Safety glasses – EMI, ESD and tools – Never work alone – Dust – Other problems

Telephony Networking

Testing Laboratories • Testing laboratory rooms and equipment – Fire, heat, humidity and moisture – Airborne contaminant – Electromagnetic – Shakers – Wind and rain – Pressure – Sound

Telephony Networking

Securing Equipment • Physically secure telephony equipment using brackets • Isolate power sources by grounding them properly – Grounding lugs – Steel rod placed roughly 6 feet in the ground – Earthing ring

Telephony Networking

Summary  Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analog and/or digital butt set, volt meter, time domain reflectometer)  Identify safety procedures for working with convergent network equipment (e.g., power, proper grounding, electrostatic discharge [ESD], radio frequency interference [RFI], electromagnetic interference [EMI])

Telephony Networking

Lesson 3: Troubleshooting

Objectives • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., inband and out-of-band signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wire-to-four-wire hybrids) • Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analog and/or digital butt set, volt meter, time domain reflectometer) • Identify symptoms of improper clocking configuration (e.g., problems with synchronization) Telephony Networking

Troubleshooting Terms • • • • •

Short (continuity) Open (open fault) Terminator Cross Polarity

• • • • •

Split Line imbalance Crosstalk Loopback testing End-to-end testing

Telephony Networking

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 set to listen to digital communications by going into "data safe mode"

Telephony Networking

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 Telephony Networking

Troubleshooting Tools (cont'd) • Multimeter – Measures resistance, current and voltage in an electrical circuit

Telephony Networking

Troubleshooting Tools (cont'd) • Punchdown tool – Inserts wires in 66 and 110 punchdown blocks • Line tester – Determines whether a short exists in a line • DTMF decoder – Can capture, convert and play back DTMF signals • Modular breakout adapter – Breaks out all wires in an RJ-11 or RJ-45 jack into individual, easily accessible wires

Telephony Networking

Troubleshooting Analog Lines • PBX and ground-start analog lines – At the PBX, use a butt set to isolate crosstalk to determine whether 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 Telephony Networking

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 • Crossed signaling methods – Lines that use in-band signaling should not be directly connected to lines that use out-ofband signaling – Failed transmissions or garbled data can result • Check for proper termination • Be aware of different ISDN voice-encoding standards Telephony Networking

Troubleshooting Digital Lines (cont'd) • Consider signal-to-noise ratio • Test equipment for digital networks – Signal/spectrum analyzer – Multimeter – Oscilloscope – Time domain reflectometer (TDR) – Service-specific test set

Telephony Networking

Troubleshooting Digital Lines (cont'd) • Telephones and ring voltage – REN value determines the ringing voltage – -90 v AC charge needed to ring a standard analog telephone – Telco will not guarantee a phone to ring if a line has to service a number of devices that together constitute more than 5 REN in North America (4 REN in the UK) • Safety – Ensure that power is connected properly at the electrical termination device. – Use a circuit breaker to guard against electrical shocks Telephony Networking

Summary  Resolve problems when connecting time division multiplexing (TDM) networks (e.g., inband and out-of-band signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wire-to-four-wire hybrids)  Identify and use appropriate troubleshooting tools (e.g., four-pair tester, tone-and-probe kit, analog and/or digital butt set, volt meter, time domain reflectometer)  Identify symptoms of improper clocking configuration (e.g., problems with synchronization) Telephony Networking

Lesson 4: Analog and Digital Signaling

Objectives • Identify basic ISDN services and protocols, including time slots, channels, ISDN2e/Basic Rate Interface (BRI), ISDN30/Primary Rate Interface (PRI) • Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wireto-four-wire hybrids) • Define the Q.931, Q.932, I.430 and Q.921/Highlevel Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.) Telephony Networking

Objectives (cont’d) • Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface • Define QSIG, H.450 (including supplementary services), Digital Access Signaling System 1 (DASS1), private networking, and Digital Private Network Signaling System (DPNSS) • Define Signaling System 7 (SS7)/Common Channel Signaling 7 (C7) functions, including call setup, management and teardown; signaling links; signaling points (e.g., service switching point [SSP], signal transfer point [STP], service control point [SCP]) Telephony Networking

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

Telephony Networking

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

Telephony Networking

Loop-Start Analog Trunk Signaling Standard phone/PBX

CO Tip (green)

Ring generator Ground Battery -48 v DC

Idle condition

Ring (red) Standard phone/PBX

CO Tip (green)

Ring generator Ground Battery -48 v DC

Ring (red)

Making a call from a standard phone

Telephony Networking

Integrated Services Digital Network (ISDN) • ISDN can carry voice, fax, imaging or data communications • Two types of ISDN: – Basic Rate Interface (BRI) – Two 64-Kbps channels for voice or data; one 16-Kbps channel for signaling – 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 Telephony Networking

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 Telephony Networking

ISDN Protocols (cont'd) • High-level Data Link Control – Link Access Protocol D channel (HDLC–LAPD) – Used in ISDN connections to provide signaling – LAPD also known as Q.921 – 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 Telephony Networking

ISDN Protocols (cont'd) Q.931 message types

Message Type

Description

Setup (SETUP)

Begins data transmission

Connect (CONNECT)

Allows terminal adapters and switches to signal each other for the call to proceed

Call proceeding (CALL PROC)

Sent by the switch to the terminal that initiated the call

Alert (ALERTING)

Used to send a signal to the calling system

Connect acknowledgement (CONNECT ACK)

Sent by the terminal being called to acknowledge that the call has been established

Telephony Networking

Private Integrated Services Network (PISN) • A private network providing services to a specific set of users (not to the general public) • Formed when digital PBXs communicate with one another over private ISDN lines • Communications can be private and encrypted • A private numbering plan can be implemented • A PINX is a piece of equipment (such as a PBX and/or other networking equipment, such as a router) used to create a PISN • PINX provides automatic connection-handling functions Telephony Networking

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

Telephony Networking

PISN Signaling Methods (cont'd) • QSIG basic call (QSIG BC)

Telephony Networking

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

Telephony Networking

Signaling System Seven (SS7) • Signaling System Seven (SS7) – a packet-switched network protocol used by telcos in calls that pass between switches • SS7 network and protocols are used for: – Basic call setup, management and teardown – Wireless services such as internetwork roaming – Toll-free and toll services – Local number portability – Enhanced calling features • High-level Data Link Control (HDLC) – a protocol that divides signaling data into discrete packets

Telephony Networking

Signaling System Seven (SS7) (cont'd)

• SS7 elements: – Service Switching Point (SSP) – Signaling Transfer Point (STP) – Service Control Point (SCP) • SS7 signaling links: – Access (A) links – connect SSPs to STPs – Bridge (B) links – connect STP pairs in the same level of the SS7 hierarchy – Cross (C) links – connect each STP in a mated pair to its mate – Diagonal (D) links – connect STP pairs on different levels of the SS7 hierarchy – Extended (E) links – connect an SSP to an alternative STP pair – Fully associated (F) links – connect mobile network SSPs directly to each other Telephony Networking

Computer-Telephony Integration (CTI) CTI – the ability for telephony networks and data networks to share data

Telephony Networking

Summary  Identify basic ISDN services and protocols, including time slots, channels, ISDN2e/Basic Rate Interface (BRI), ISDN30/Primary Rate Interface (PRI)  Resolve problems when connecting time division multiplexing (TDM) networks (e.g., in-band and out-of-band signaling, digital and analog setup messages, safety practices and standards, crosstalk, split, line imbalance, open, short, grounding issues, echo cancellation in two-wireto-four-wire hybrids)  Define the Q.931, Q.932, I.430 and Q.921/Highlevel Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.) Telephony Networking

Summary (cont’d)  Explain the purpose of network termination equipment (NTE), including timing, conversion of signaling types, troubleshooting interface  Define QSIG, H.450 (including supplementary services), Digital Access Signaling System 1 (DASS1), private networking, and Digital Private Network Signaling System (DPNSS)  Define Signaling System 7 (SS7)/Common Channel Signaling 7 (C7) functions, including call setup, management and teardown; signaling links; signaling points (e.g., service switching point [SSP], signal transfer point [STP], service control point [SCP]) Telephony Networking

Telephony Networking    

Telephony Essentials Boundaries, Numbers, Wiring and Safety Troubleshooting Analog and Digital Signaling

Telephony Networking