3

About now!

2000

x5

2005

x23Voice and Data Growth

DataTraffic

Time

Voice

4

Today’s Mixed Networks

VirtualPrivate

Networks

ManagedNetworkServices

InternetServices

WirelessServices

IP

Frame RelayATM

VoiceServices Voice-centric

Infrastructure

Transport

5

The Converging Network

VirtualPrivate

Networks

ManagedNetworkServices

InternetServices

WirelessServices

IP

FR + ATM

VoiceServices

Legacy Infrastructure

6

Frost & Sullivan predict - 4/98

'97 '98 '99 '00 '01 '020

2

4

6

8

10

Min

ute

s p

er M

on

th

(Bill

ion

)

'97 '98 '99 '00 '01 '02

IP telephony world traffic

7

Little affect on PSTN

'97 '98 '99 '00 '01 '020%

20%

40%

60%

80%

100%

'98 '99 '00 '01 '02

World telephony traffic

IP

PSTN

Frost & Sullivan, April 1998

8

VoIP Standards & Organizations

ITU-T—H.323

IMTC—VoIP

IETF— MGCP, SIP, RSVP, RTCP, RTP

9

Intranet TelephoneNetwork

GatekeeperGatekeeperH.323 TerminalH.323 Terminal

RouterRouterProxyProxy

GatewayGateway

H.320H.320(Over ISDN)(Over ISDN)

H.324H.324(Over POTs)(Over POTs)

Speech OnlySpeech Only(PSTN)(PSTN)

H.323H.323

Corp LANCorp LAN

V

V

Real-Time Network

H.323 Infrastructure

ITU H.323 for VoIP

System Control

H.245 Control

Call Control H.225.0

RAS Control H.225.0

Video CodecH.261, H263

User DataApplications

T.120

H.225.0 Layer

AudioI/O

Equipment

Audio CodecG.711, G.722,

G.723, G.723.1, G.728, G.729

Receive Path Delay

System Control and

User Interface

VideoI/O

Equipment

Session Layerand Above

10

LAN Stack309-E1171_04F8_c1

11

H.323 Standard suite

• H.323: overall architecture

• H.225: Call control, RAS

• H.235: Security for H.323 term

• H.332: Large group conferences

• H.450: Supplementary services

• H.246: Interworking with H.xxx

• Q.931: ISDN call control

12

What is an H.323 Gateway?

H.323Terminal

Non-H.323Terminal

H.323Endpoint

Non-H.323

Endpoint

ProtocolTranslation

andMedia

Transcoding

H.323 Gateway

13

PBX

EthernetVoIP/DSP’s

TDM

Types of Voice over IP Gateways in the Enterprise

VoIP/DSP’s

TDM

VoIP/DSP’s

WAN, Intranet, Internet

PSTN

14

Ethernet

VoIP/DSP’s

PC-Based

High DensityAccess Device

POP

WAN, Intranet, Internet

PSTN

Switch

VoIP/DSP’s

VoIP/DSP’s

VoIP Gateways for Service Providers

15

RAS

H.323Terminal

DNS

H.323Gatekeeper

Tacacs/Radius

H.323 Gatekeeper

RegistrationRegistrationRegistrationRegistration

BandwidthBandwidthManagementManagementBandwidthBandwidth

ManagementManagement

Admission/Admission/CallCall

RedirectionRedirection

Admission/Admission/CallCall

RedirectionRedirection

RegistrationRegistrationDatabaseDatabase

RegistrationRegistrationDatabaseDatabase

CallCallRedirectionRedirectionDatabaseDatabase

CallCallRedirectionRedirectionDatabaseDatabase

RASRASDispatchDispatch

RASRASDispatchDispatch

IPIPFRFR ATMATM

VOICEVOICE

16

H.323 Gatekeeper Functions

• Mandatory services:

Address translation

Admissions control

Bandwidth control

Zone management

• Optional services:Call control signalling

Call authorization

Call management

Gatekeeper management information data structure

Directory services

RAS- Registration, Admission and Status

17

Signalling phases

• Gateway discovery

• Endpoint registration

• Call setup

• Initial communication and capability exchange

• Establishment of audio visual communication

• Call services : bandwidth change, status, Ad Hoc conference, call termination

• Call termination

18

Direct endpoint call signalling

Endpoint 1

Endpoint 2

Gatekeeper cloud

1)ARQ 2)ACF 4)ARQ 5)ACF

3)Setup

6)Connect

19

Gatekeeper routed call signalling

Endpoint 1

Endpoint 2

Gatekeeper cloud

1)ARQ

2)ACF

5)ARQ6)ACF

3)Setup

8)Connect

4)Setup7)Connect

20

Call Control

• Three Types

Intelligent gateway

Gateway initiated/intelligent network (H.323 gatekeeper)

Intelligent network (SGCP/IPDC)

PBX

PBX

PBX

21

dial-peer voice 24 voipdial-peer voice 24 voipdestination-pattern +8....destination-pattern +8....session target session target ipv4:204.94.142.130ipv4:204.94.142.130

V

IntranetV

V

8432184321204.94.142.130204.94.142.130

Intelligent Gateway

• Call control and call handling in the gateway

• Each gateway knows about the others

• The DialPeers map dialed numbers to IP addresses

• SIP is also an intelligent endpoint

22

GatekeeperGatekeeper

Traffic Flow

Call Setup

PBX

PBX

PBX

V

V

V

Gateway Initiated Calls—H.323 Gatekeeper

• Defined by H.323

• Gateways register with gatekeeper

• Gateways initiate calls but do not know about other gateways

• Telephony E.164-style addresses mapped to IP addresses by gatekeeper

• H.323 gatekeepers allow scaling

23

IP Network

PBXPBX

Virtual Connection (per call)End-to-end Services

Signaling / Backhaul

Bearer Control

PBXPBX

SGCP

H.323SIP

Call Agent

VirtualVirtualSwitchSwitch

VV

Voice

V

V

Intelligent Network (Future)

24

IP Network

Virtual Connection (per call)End-to-end Services

Signaling / Backhaul

Bearer Control

PBXPBX

Intra-Virtual Switch Signaling

SGCP

PSTN/SS7 PSTN/SS7

H.323SIP

Call Agent

Voice GW

VirtualVirtualSwitchSwitch

SN, ACD, etc.SN, ACD, etc.

Call Agent

VV

IN or DatabaseIN or Database

SS7 Signaling

Intelligent Network (Future)

25

RTP/RTCP—RFCs 1889/1890

• End-to-end network transport function Payload type identification - Voice, Video, Compression Type

Sequence numbering

Time Stamping

Delivery monitoring

• RTCP (Real-Time Control Protocol) provides feedback on the quality of the distribution

RTP Timestamp

Synchronization Source (SSRC) ID

4bytes

4bytes

4bytes

Sequence NumberPayload

TypeMCC

VER

26

RTP Controlling Dejitter Buffer

RTP Timestamp From Router AInterframe gap of 20ms

AA

Sender Receiver

IPNetwork

VV VV

BB CC

RouterA RouterB

10 30 50

20ms 20ms

RTP Timestamp From Router AVariable Interframe Gap (Jitter)

AA BB CC10 30 50

20ms 80ms

RTP Timestamp From Router ADelitter Buffer removes Variation

AA BB CC10 30 50

20ms 20ms

• Background noise

• Silence suppressionComfort noise

• Language sensitivity

• Subjective quality (MOS)MOS

• Delay and delay variation

• Echo cancellation

Voice Transport Requirements

Loss

Bandwidth

Delay

VoIP Challenges in the WAN

27

28

missin

g p

acket

G.729 vocoder algorithm

VoIP (G.729) Is Tolerant of “Occasional” Packet Loss

• The friendly “retransmission” is of no use in the Voice world… late is as good as never

• Complex “concealment strategy” in algorithm interpolates lost packets based on context

29

How Does Echo Happen?

• Echo is due to a reflection

Impedance mismatch at the 2w-4w hybridis the most common reason for echo

2 Wire Local Loop

Central Office

2w-4wHybrid

ReceiveDirection

TransmitDirection

Rx & TxSuperimposed

Echo is always present and as a problem is a functionof the echo delay, and the magnitude of the echo

Echo is always present and as a problem is a functionof the echo delay, and the magnitude of the echo

30

Delay—How Much Is Too Much?

Cumulative Transmission Path Delay

Time (msec)

0 100 200 300 400

CB ZoneCB Zone

Satellite QualitySatellite Quality

Fax Relay, BroadcastFax Relay, BroadcastHigh QualityHigh Quality

Delay Target

500 600 700 800

ITU’s G.114 Recommendation = 0 – 150msec 1-way delay

network convergence

Documents

ms v v

intranet v v

setuppbx pbx pbx v v

ras control

control signalling

endtoend services

gatekeeper ras

gatekeeper gateways