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IWF and CCF for VoIP Protocols

Ming-Feng Chang

Professor

CSIE, NCTU

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VoIP

• Voice over IP – transport of telephone calls using IP– telephony devices, multimedia PCs or dedicated

terminals

• The benefits– a single infrastructure for Internet access and

Internet telephony– saving money– easily integrated with other services and

applications

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• The problems– lower quality of voice over IP

• higher delay and jitter

– accounting, billing, charging, roaming etc. remain open

– Interworking functions• ISUP, Q.sig, H.323, SIP and MGCP/MEGACO

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A Converged Network Architecture

• ICA – integrated call agent– A GK, SIP proxy server, and CA/MGC

3GPLMN

PSTN

IP Network

H.323 SIP

CSCF

MGW

Signaling GW

ICA 1 ICA 2

MGW

Signaling GW

PSTN

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The Interworking Functions

• PSTN– ISUP, Q.sig

• IP networks– H.323, SIP

• MGCP/MEGACO– Trunking gateways– Access gateways– Residential gateways

• Communication between any devices– The interworking function

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Half-Call Call State Model of IN

• Originating FSM• Terminating FSM

– The switching system - an MGC or IWF

Telephone/IP phone Telephone/IP phone

OriginatingFSM

TerminatingFSM

OriginatingFSM

TerminatingFSM

Switching System Switching System

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The Interactions of the FSMs

1. O_Null

2. Col_Info

3. Ana_Info

4. Routing

5. O_Active

1. T_Null

2. Sel_Fac

3. T_Alert

4. T_Active

6. O_Dis

5. T_Dis

7. O_Ab

1.Setup

2.Busy

4.NoAns

3.Alert

5.Answer

6.Disconnect

7.Disconnect

8.Abandon8. O_Ex

6. T_Ex

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The Interactions (Normal)

1. O_Null

2. Col_Info

3. Ana_Info

4. Routing

5. O_Active

1. T_Null

2. Sel_Fac

3. T_Alert

4. T_Active

6. O_Dis

5. T_Dis

7. O_Ab

1.Setup

3.Alert

5.Answer

6.Disconnect

7.Disconnect

8. O_Ex6. T_Ex

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The Interactions (Fail)

1. O_Null

2. Col_Info

3. Ana_Info

4. Routing

5. O_Active

1. T_Null

2. Sel_Fac

3. T_Alert

4. T_Active

6. O_Dis

5. T_Dis

7. O_Ab

2.Busy

4.NoAns

8. O_Ex6. T_Ex

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An Interworking Architecture

• We have developed half-call BCSMs– SIP, H.323, MGCP, and MEGACO

OriginatingBCSMs

TerminatingBCSMs

SIPO_BCSM

SIPT_BCSM

H.323O_BCSM

H.323T_BCSM

MGCPO_BCSM

MGCPT_BCSM

Events

SIP Messages

H.323 Messages

MGCP Messages

SIP Messages

H.323 Messages

MGCP Messages

SIP user agent

H.323 endpoint

MGW

SIP user agent

H.323 endpoint

MGW

OriginatingBCSMs

TerminatingBCSMs

SIPO_BCSM

SIPT_BCSM

H.323O_BCSM

H.323T_BCSM

MGCPO_BCSM

MGCPT_BCSM

Events

SIP Messages

H.323 Messages

MGCP Messages

SIP Messages

H.323 Messages

MGCP Messages

SIP user agent

H.323 endpoint

MGW

SIP user agent

H.323 endpoint

MGW

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The Integrated IWF and CCF

• Integrate CA/MGC, GK and SIP proxy server

MGCPOFSM

H323OFSM

ISUPOFSM

SIPOFSM

MGCPTFSM

H323TFSM

ISUPTFSM

SIPTFSM

Events• busy• alerted• no answer• answered• disconnected• abandoned• suspend• resume

Q.931OFSM

Q.931OFSM

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SIP-H323 IWF

SIPOFSM

SIPTFSM

H323TFSM

H323OFSM

Events• busy• alerted• no answer• answered• disconnected• abandoned

• The IWF for SIP and H.323– A GK and SIP proxy server

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VoIP Gateways

• H.323, SIP and MEGACO/MGCP

SIP/H323Gateway

SIP/MGCPGateway

CA/MGC

MediaGateway

Telephone

H323/MGCPGateway

GKH.323Phone

SIPProxy

SIPPhone

H.323 network

SIP network

MGCP network

SIP/H323Gateway

SIP/MGCPGateway

CA/MGC

MediaGateway

Telephone

H323/MGCPGateway

GKH.323Phone

SIPProxy

SIPPhone

H.323 network

SIP network

MGCP network

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The Integrated CA Design

MGCPOFSM

MGCPTFSM

SIPTFSM

ISUPTFSM

SIPOFSM

H323TFSM

H323OFSM

ISUPOFSM

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MGCP-SIP IWF/GW

MGCPOFSM

MGCPTFSM

SIPTFSM

SIPOFSM

• Inter-CA and intra-CA call setup

Intra-CA Inter-CA

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Inter-zone Communications

• Support inter-ICA call setup

MediaGateway

H.323

Zone

SIPICA

H.323O_BCSM

SIPT_BCSM

ZoneICA

SIPO_BCSM

MGCPT_BCSM

MediaGateway

H.323

Zone 1

SIPICA 1

H.323O_BCSM

SIPT_BCSM

Zone 2ICA 2

SIPO_BCSM

MGCPT_BCSM

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MGCP Half-Call Model

O_Null

O_Collec_Info

O_Routing

O_Active

O_Disconnect

T_Null

T_Present_Call

T_Active

T_Alerting

T_Disconnect

NTFY:HD

RQNT

NTFY:digits

CRCX:reconly

MDCX:RT

MDCX:sendrec

NTFY:HU

DLCX

CRCX:RG

NTFY:HD

MDCX:

DLCX:E

SetupAlert

Answer

Disconnect

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H.323 Half-Call Model

O_Null

O_Collec_Info

O_Routing

O_Active

O_Disconnect

T_Null

T_Present_Call

T_Active

T_Alerting

T_Disconnect

Setup

CallProc

Alert

H.245 EX

Release

CallProc

Connect

H.245 EX

Release

SetupAlert

Answer

Disconnect

Connect

Alert

Setup

SDP

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SIP Half-Call Model

O_Null

O_Collec_Info

O_Routing

O_Active

O_Disconnect

T_Null

T_Present_Call

T_Active

T_Alerting

T_Disconnect

INVITE (SDP)

100 Trying

180 Ringing

ACK

BYE

100 Trying

200 OK (SDP)

ACK

BYE

SetupAlert

Answer

Disconnect

200 OK (SDP)

180 Ringing

INVITE (SDP)

200 OK 200 OK

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MEGACO Half-Call Model

O_Null

O_Collec_Info

O_Routing

O_Active

O_Disconnect

T_Null

T_Present_Call

T_Active

T_Alerting

T_Disconnect

Notify:of

Modify:digitmap,on

NTFY:digits

Add:rt,reconly

Modify:sendrec,sdp2

Notify:on

Add:ri,sendrec,sdp1

Notify:of

Modify: ,on

Subtract:ct,on

Setup(sdp1)

Alert

Answer(sdp2)

Disconnect

Reply:sdp1

Reply:sdp2

Subtract:of

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MGW FSMs

• Media Gateways– Trunking GWs– Access GWs– Residential GWs

• OFSMs and TFSMs– For TGWs, AGWs, and RGWs

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Examples

• Our VoIP platform

IP Network

H.323 SIP

CA CA

AGW

PSTN

RGW

Telephone

SIP UA

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Examples

• Communications between any devices

PSTN

IP Network

H.323 SIP

TGW

Signaling GW

CA MGC

MGW

Signaling GW

PSTN

RGW

Telephone

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Conclusions

• The interworking functions are important– ISUP, Q.sig, H.323, SIP and MGCP/MEGACO

• Half-call model– For the integrated IWF and CCF

• Gateway selection?– iptel

• Mobility support?