1 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony Introduction to Packet Voice Technologies Cisco Networking Academy Program

2 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Traditional Telephony

3 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Basic Components of a Telephony Network

4 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Central Office Switches

5 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 What Is a PBX?

6 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Basic Call Setup

7 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Supervisory Signaling

8 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Address Signaling Tone telephone DTMF dialing Rotary telephone –Pulse dialing

9 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Informational Signaling

10 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Digital vs. Analog Connections

11 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Time-Division Multiplexing

12 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Frequency-Division Multiplexing

13 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Packetized Telephony Networks

14 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Packet Telephony vs. Circuit-Switched Telephony More efficient use of bandwidth and equipment Lower transmission costs Consolidated network expenses Increased revenue from new services Service innovation Access to new communications devices Flexible new pricing structures

15 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Call Control

16 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Distributed Call Control

17 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Centralized Call Control

18 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Packet Telephony Components

19 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Real-Time vs. Best-Effort Traffic Real-time traffic needs guaranteed delay and timing. IP networks are best-effort with no guarantees of delivery, delay, or timing. Solution is quality of service end-to-end.

20 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Foreign Exchange Station Interface

21 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Foreign Exchange Office Interface

22 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Interface

23 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 T1 Interface

24 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E1 Interface

25 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 BRI

26 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Physical Connectivity Options

27 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Cisco IP Phone

28 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Analog Voice Basics

29 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Local Loops

30 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Types of Local-Loop Signaling Supervisory signaling Address signaling Informational Signaling

31 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 On Hook

32 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Off Hook

33 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Ringing

34 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Ringing (Cont.)

35 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Pulse Dialing

36 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Dual Tone Multifrequency

37 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Informational Signaling with Call-Progress Indicators

38 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Trunks

39 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Foreign Exchange Trunks Foreign Exchange Office Connects directly to office equipment Used to extend connections to another location Foreign Exchange Station Connects directly to station equipment Used to provision local service

40 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Types of Trunk Signaling Loop start Ground start E&M Wink Start E&M immediate start E&M delay start

41 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Loop-Start Signaling

42 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Ground-Start Signaling

43 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Signaling Separate signaling leads for each direction E-lead (inbound direction) M-lead (outbound direction) Allows independent signaling

44 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Type I

45 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Type V

46 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Type II

47 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Type III

48 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E&M Type IV

49 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Trunk Supervisory Signaling— Wink Start

50 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Trunk Supervisory Signaling— Immediate Start

51 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Trunk Supervisory Signaling— Delay Start

52 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 2-Wire to 4-Wire Conversion and Echo Echo is due to a reflection. Impedance mismatch at the 2-wire to 4-wire hybrid is the most common reason for echo.

53 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Echo Is Always Present Echo as a problem is a function of the echo delay and the loudness of the echo.

54 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Echo Suppression

55 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Echo Cancellation

56 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Analog-to-Digital Voice Encoding

57 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Digitizing Analog Signals 1.Sample the analog signal regularly. 2.Quantize the sample. 3.Encode the value into a binary expression. 4.Compress the samples to reduce bandwidth, optional step.

58 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Basic Voice Encoding: Converting Digital to Analog 1.Decompress the samples, if compressed. 2.Decode the samples into voltage amplitudes, rebuilding the PAM signal. 3.Filter the signal to remove any noise.

59 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Nyquist Theorem

60 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Voice Compression Techniques Waveform algorithms PCM ADPCM Source algorithms LDCELP CS-ACELP

61 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Example: Waveform Compression PCM Waveform coding scheme ADPCM Waveform coding scheme Adaptive: automatic companding Differential: encode changes between samples only ITU standards: G.711 rate: 64 kbps = (2 * 4 kHz) * 8 bits/sample G.726 rate: 32 kbps = (2 * 4 kHz) * 4 bits/sample G.726 rate: 24 kbps = (2 * 4 kHz) * 3 bits/sample G.726 rate: 16 kbps = (2 * 4 kHz) * 2 bits/sample

62 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Compression Bandwidth Requirements

63 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Mean Opinion Score

64 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Perceptual Speech Quality Measurement

65 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Signaling Systems

66 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 T1 Digital Signal Format

67 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Robbed-Bit Signaling

68 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Channel Associated Signaling—T1

69 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 E1 Framing and Signaling

70 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Channel Associated Signaling—E1

71 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Common Channel Signaling

72 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 ISDN Part of network architecture Definition for access to the network Allows access to multiple services through a single access Used for data, voice, or video Standards-based ITU recommendations Proprietary implementations

73 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 ISDN Network Architecture

74 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0 Layer 3 (Q.930/931) Messages

75 © 2005 Cisco Systems, Inc. All rights reserved. Cisco Public IP Telephony v1.0