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Telephony Networking. Lesson 1: Telephony Essentials.

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Presentation on theme: "Telephony Networking. Lesson 1: Telephony Essentials."— Presentation transcript:

1 Telephony Networking

2 Lesson 1: Telephony Essentials

3 Telephony Networking 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, , real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

4 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-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)

5 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

6 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 telephone- numbering system Direct Inward Dialing (DID) / Direct Dialing Inward (DDI) – enables multiple telephone numbers to be used on a few lines

7 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

8 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, , voice mail and fax, in a centralized server

9 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

10 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, , chat or instant messaging, and Web (click-to-talk)

11 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

12 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

13 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”

14 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

15 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 long- distance 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

16 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

17 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

18 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

19 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, , real-time voice and data recording/storage, hosted solutions, and elements of Computer Telephony Integration (CTI)

20 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-wire- to-four-wire hybrids)

21 Lesson 2: Boundaries, Numbers, Wiring and Safety

22 Telephony Networking 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])

23 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

24 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

25 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

26 Telephony Networking RJ-11 Connectors and Wiring

27 Telephony Networking RJ-12 Modular Connector

28 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

29 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

30 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

31 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

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

33 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

34 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])

35 Lesson 3: Troubleshooting

36 Telephony Networking Objectives 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-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)

37 Telephony Networking Troubleshooting Terms Short (continuity) Open (open fault) Terminator Cross Polarity Split Line imbalance Crosstalk Loopback testing End-to-end testing

38 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"

39 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

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

41 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

42 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

43 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-of- band signaling –Failed transmissions or garbled data can result Check for proper termination Be aware of different ISDN voice-encoding standards

44 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

45 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

46 Telephony Networking Summary 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-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)

47 Lesson 4: Analog and Digital Signaling

48 Telephony Networking 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-wire- to-four-wire hybrids) Define the Q.931, Q.932, I.430 and Q.921/High- level Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.)

49 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])

50 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

51 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

52 Telephony Networking Loop-Start Analog Trunk Signaling

53 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) – 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

54 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

55 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

56 Telephony Networking ISDN Protocols (cont'd) Q.931 message types Message TypeDescription 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

57 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

58 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

59 Telephony Networking PISN Signaling Methods (cont'd) QSIG basic call (QSIG BC)

60 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

61 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

62 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

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

64 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-wire- to-four-wire hybrids) Define the Q.931, Q.932, I.430 and Q.921/High- level Data Link Control (HDLC) standards, including identifying the typical call progress signals (e.g., alerting, call proceeding, etc.)

65 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])

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


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