smben20s05l01

7/28/2019 SMBEN20S05L01

1/28

2008 Cisco Systems, Inc. All rights reserved. SMBEN v2.05-1

Voice Technologies

7/28/2019 SMBEN20S05L01

2/28


Module Overview

This module gives an overview of the standard telephonytechnologies and introduces the Cisco IP telephony andthe Cisco Unified Communications technology.

Upon completing this module, you will be able to describe

basic telephony concepts, including IP telephony andUnified Communications. This ability includes being ableto meet these objectives:

Explain traditional telephony basics and Cisco VoIP functionality,and apply telephony concepts to trunking options

Define infrastructure and components for IP telephony and CiscoUnified Communications

7/28/2019 SMBEN20S05L01

3/28


Voice Technologies

Telephony BasicsOverview ofTelephony

7/28/2019 SMBEN20S05L01

4/28


Lesson Overview

Upon completing this lesson, you will be able to:

Describe the components of traditional telephony network

Explain the primary differences between a PBX and aKey System

Explain common telephony features

List and describe the terms used to describe a telephonyconnection

Describe the functionality of gateways and their role ofconnecting IP to traditional PSTN and telephony equipment

Explain the primary differences between analog and digitaltrunking options

Describe the major VoIP signaling protocols, H.323, SIP,and SCCP

7/28/2019 SMBEN20S05L01

5/28


Traditional Telephony Overview

7/28/2019 SMBEN20S05L01

6/28


Important Telephony Terms

DTMF dual tone multifrequency

ITU International Telecommunications Union

ETSI European Telecommunications Standards Institute

Local Loop

Trunk

Tie Line Trunk

Central Office = CO (Local Exchange)

POTS plain old telephone service

PCM pulse code modulation

TDM time-division multiplexing

codec coder and decoder

DSP digital signal processor

7/28/2019 SMBEN20S05L01

7/28 2008 Cisco Systems, Inc. All rights reserved. SMBEN v2.05-7

Basic Components of a TraditionalTelephony Network

Outsidecalls

In-housecalls

BostonSan Jose

EdgeDevices

Exchange Exchange

Tie Trunk

ExchangeTrunks

LocalLoop

LocalLoop

Switch Switch

PBX PBX

Tie Trunk

ExchangeTrunks

PSTN

7/28/2019 SMBEN20S05L01


Pulse Code Modulation

Initial signal is analog

Analog signal converted to digital, 8 bit word format

0 0 1 1 0 0 0 1

Band Limiter,Sampler,

Quantization

Analog Signal Digital Signal

8 bit word 8 bit word.

7/28/2019 SMBEN20S05L01


Time-Division Multiplexing

Provides a mechanism for transporting multiple callsbetween two points on a common carrier

Used by CAS and ISDN trunks in customer access networks andforms the basis of service-provider networks

Conversation 1

Conversation 2

Conversation 3

Conversation 4

Conversation 24/30

11 11 1

3 3 3 3 3

4 4444

24 24 2424

2 2 2 2 24 3 12 24 4 3 12

Carrier Channel

7/28/2019 SMBEN20S05L01


PBX Functionality

PBX

Line Trunk LocalExchangeTerminal interface Terminal interface

Switching network Terminal interface

Control complex Terminal interface

Power supply andfans Terminal interface

LineCard

Trunkcard

7/28/2019 SMBEN20S05L01


Key System Functionality

Keysystem

TrunksTerminationblocks

RJ-11

LocalExchange

CO line cards

Station cards

Station cards

Intercom cardsPower supply

Main distribution frame

7/28/2019 SMBEN20S05L01


Comparing PBXs with Key Systems

Comparing Key Systems with PBXs

PBX Key System

Technology Primarily digital Analog or digital

Switch functionality Similar to the CO switch Not a switch

Typical installationLarge company site(typically more than 50 users)

Small company or branchoffice(typically 50 users or fewer)

Method for AccessingOutside Trunks Dial 9 or other access numberto access outside line Press a button to accessoutside line

7/28/2019 SMBEN20S05L01


Common PBX Features

Shared lines or shared DN

Hunt groups

Monitor lines

Intercom lines

Audio paging

Speed dial

Overlaid lines

7/28/2019 SMBEN20S05L01


Introducing Voice over IP

7/28/2019 SMBEN20S05L01


Using IP as a Transport Medium forTelephony

IP networks are better suited tomultimedia networks as they can usebandwidth more efficiently than TDMnetworks.

A voice gateway is used to interfaceTDM PBXs and the PSTN with IPnetworks.

Voice gateways are often used to:

Transfer wide-area TDM traffic toan IP network.

Connect IP PBX systems to thePSTN or analog endpoints.

Gateways can support analog ordigital telephony interfaces.

7/28/2019 SMBEN20S05L01


Analog Voice Ports

FXS: Connects directly to end-user equipment such as telephones, faxmachines, or modems

FXO: Used for trunk, or tie line, connections to a PSTN CO or to a PBX thatdoes not support E&M signaling

E&M: Used for private PBX-to-PBX connectivity

FXS

PSTNFXOFXO

E&M E&MWAN orPSTN

7/28/2019 SMBEN20S05L01


Digital Voice Ports

T1-CAS: Supports 24 voice channels. Signaling is embedded inthe voice channel.

T1-PRI: Supports 23 voice (B) channels. Signaling is carried in adedicated 64kbps data (D) channel.

E1-CAS: Supports 30 voice channels. Signaling is transported ina dedicated signaling channel.

E1-PRI: Supports 30 voice (B) channels. Signaling is carried in adedicated 64kbps data (D) channel.

Basic Rate ISDN (BRI): Supports 2 voice (B) channels. Signaling

is carried in a dedicated 16kbps data (D) channel.

7/28/2019 SMBEN20S05L01


Gateway Features

Gateways support multiple IP protocols such as:

H.323

SIP

SCCP

Gateways also provide additional functionality

DTMF relay

Supplementary services

Provide fax and modem services, or both

7/28/2019 SMBEN20S05L01

19/28

Signaling Protocols

Protocol Description

H.323ITU standard protocol for interactive conferencing; evolved fromH.320 ISDN standard; flexible, complex

SIPIETF protocol for interactive and non-interactive conferencing; simpler,but less mature, than H.323

SCCPCisco protocol used by Unified Communications Manager and UnifiedCommunications Manager Express to control telephony endpoints.

7/28/2019 SMBEN20S05L01


H.323

H.323 suite:

Approved in 1996 by the ITU-T

Peer-to-peer protocol where end devices initiate sessions

Widely used with gateways, gatekeepers, or third-party H.323

clients, especially video terminals in Cisco UnifiedCommunications

7/28/2019 SMBEN20S05L01


Session Initiation Protocol (SIP)

SIP Attributes:

IETF RFC 2543 (1999), RFC 3261 (2002)

Based on the logic of the World Wide Web

Widely used with gateways and proxy servers within service

provider networks Peer-to-peer protocol where end devices (user agents) initiate

sessions

ASCII text-based for easy implementation and debugging

7/28/2019 SMBEN20S05L01


How SIP Works

ASCII-based protocol.

User identified by a unique SIP address.

sip:[email protected]

Users optionally register with a registrar server using their

assigned SIP addresses. When a user initiates a call, a SIP request is sent to a SIP server.

Location of end user can be dynamically registered with the SIPserver.
http://sip:[email protected]/http://sip:[email protected]/

7/28/2019 SMBEN20S05L01


Advantages of SIP Gateways

Dial plan configuration directly on the gateway

Translations defined per gateway

Advanced support for third-party telephony system integration

Interoperability with third-party voice gateways

Support of third-party end devices (SIP phones)

7/28/2019 SMBEN20S05L01


Skinny Call Control Protocol (SCCP)

Cisco proprietary lightweight client protocol used by:

Cisco Unified Communications Manager

Cisco Unified Communications Manager Express

Client messaging set controls:

Registration

Management

Call control

Media control

7/28/2019 SMBEN20S05L01

25/28


Q&A

7/28/2019 SMBEN20S05L01

26/28


Lesson Summary

7/28/2019 SMBEN20S05L01

27/28


Lesson Summary

An underlying knowledge of the basic terminology, components,and features of traditional telephony is necessary for engineers.

Small organizations and branch offices often use a key telephonesystem because a PBX offers functionality and extra features thatmay not be required.

A voice gateway is used to interface TDM PBXs and the PSTNwith PT networks.

Cisco analog station gateways connect an IP telephony networkto POTS, whereas Cisco access digital trunk gateways connectan IP telephony network to the PSTN via digital trunks.

Cisco voice gateways support various signaling protocols,depending on the hardware platform.

7/28/2019 SMBEN20S05L01

28/28

smben20s05l01

Documents