CISCO -- Introduction to Voice Over IP and Other Integrated Services -- Session 408 - (2000)

1

Cisco Systems Confidential

14081038_05F9_c2 © 1999, Cisco Systems, Inc. 14081038_05F9_c2 © 1999, Cisco Systems, Inc.

2© 1999, Cisco Systems, Inc. 4081038_05F9_c2

Introduction to Voice overIntroduction to Voice overIP and other IntegratedIP and other Integrated

ServicesServicesVoice Signaling Is the KeyVoice Signaling Is the Key

to Enhanced Servicesto Enhanced Services

Session 408Session 408

2


34081038_05F9_c2 © 1999, Cisco Systems, Inc.

AgendaAgenda

• Analog/Digital Signaling

• ISDN/SS7 Signaling

• QSIG

• H.323

• SIP

• Media Gateway Controller


In the Beginning—Well Almost!In the Beginning—Well Almost!

3



T

R

Called Station

R

T

Calling Station

TelephoneNetwork

R - RingT - Tip

SwitchSwitch

SwitchSwitch

Line Signaling: On-HookLine Signaling: On-Hook


T

R

Called Station

R

T

Calling Station

TelephoneNetwork

R - RingT - Tip

SwitchSwitch

SwitchSwitch

Line Signaling: Off-HookLine Signaling: Off-Hook

1. Signaling supervision

4



T

R

Called Station

R

T

Calling Station

TelephoneNetwork

R - RingT - Tip

Dial-ToneDial-Tone

SwitchSwitch

SwitchSwitch

Line Signaling: Dial-ToneLine Signaling: Dial-Tone

2. Call information (network to user)


T

R

Called Station

R

T

Calling StationR - RingT - Tip

Tones orPulses

Tones orPulses

SwitchSwitch

SwitchSwitch

Line Signaling: AddressingLine Signaling: Addressing

3. Dialing the destination

TelephoneNetwork

5



SwitchSwitch

SwitchSwitch

T

R

R

T

Calling Station

TelephoneNetwork

R - RingT - Tip

Ring BackRing Back

RingGenRingGen

SwitchSwitch

SwitchSwitch

Line Signaling: RingingLine Signaling: Ringing

4. Call information (network to user)

Called Station

RingingRinging


T

R

Called Station

R

T

Calling Station

TelephoneNetwork

R - RingT - Tip

300–3400 Hz @ 4khz

SwitchSwitch

SwitchSwitch

Line Signaling: Off-HookLine Signaling: Off-Hook

5. Call Completion

6



Loop Start

FXSFXS FXSFXS

Loop Start

Loop Start

FXSFXS

Loop StartPBXPBX

FXOFXO

Applications of Line SignalingApplications of Line Signaling


RT

R1

T1

T

R

RT

R1

T1

R - RingT - TipR1 - Ring 1T1 - Tip 1

PBXPBX SwitchSwitch PBXPBXSwitchSwitch

Trunk SignalingTrunk Signaling

• Loop Start

• Ground Start

• E&M

7



FXOFXO FXSFXS

LATA 1 LATA 2591-XXXX 555-XXXX

Loop StartLoop Start

Caller Calls 591-4242and the Call Appears

as a Local Call

PBXPBXSwitchSwitch

Application—Foreign ExchangeApplication—Foreign Exchange(Loop Start)(Loop Start)

• Limitations:Simultaneous trunk seizure (glare)

Lack of far-end disconnect notification


2. CO switch senses the ground

Ground Sensor

Ground Start SupervisoryGround Start SupervisorySignaling—From PBXSignaling—From PBX

Off-Hook

PBXPBXTelephoneSwitch

TelephoneSwitch

- 48 VDC

R - RingT - Tip

R

T

Tip GroundDetector

Off-Hook

- 48 VDC

1. PBX grounds the ring lead

3. CO switch grounds the tip lead

4. PBX sensing the ground, closes the loop, removes ring ground

8



FXOFXO FXSFXS

LATA 1 LATA 2591-XXXX 555-XXXX

Ground StartGround Start

Caller Calls 591-4242and the Call Appears

as a Local Call

PBXPBXSwitchSwitch

Application—Foreign ExchangeApplication—Foreign Exchange(Ground Start)(Ground Start)


Ground Start BenefitsGround Start Benefitsand Limitationsand Limitations

• Benefits

Reduces glare by quickly recognizingincoming seizure (tip ground)

Provides remote disconnect supervision

• Limitations

Mixed voice and signaling

Tip and ring cannot be reversed

CO switch and PBX must have samepotential ground

9



T and T1

R and R1

EM

TR

EM

2 Wire E&M 4 Wire E&M

SignalingInterfaceExchange

SignalingInterfaceExchange

Ear and Mouth (E&M)Ear and Mouth (E&M)Separate Signaling PathSeparate Signaling Path

• 2 wire and 4 wire refer to the voice wires

• The switch listens on the ear (E-lead)

• The switch signals on the mouth (M-lead)

PBXPBX CO SwitchCO Switch


LineLineEquipmentEquipment

M- 48 VDCOff-Hook

- 48 VDC

M

E E

GroundOn-Hook

E-LeadDetector

M-LeadDetector

2-Wire, Nonsymmetrical

PBXPBX

OpenOn-Hook

GroundOff-Hook

E&M Type 1E&M Type 1

• Common ground must exist betweenPBX and line equipment

10



E&M TypeE&M Type

Type I Type I

Off-HookOff-Hook

Type II Type II

Type III Type III

Type IV Type IV

Type V Type V

E&M Signaling StatesE&M Signaling States

E-Lead/SGE-Lead/SGM-Lead/SBM-Lead/SBConditionCondition

OpenOpenGroundGroundOn-HookOn-Hook

GroundGroundBatteryBattery

Off-HookOff-Hook GroundGroundBatteryBattery

OpenOpenOpenOpenOn-HookOn-Hook

OpenOpenGroundGroundOn-HookOn-Hook

Off-HookOff-Hook GroundGroundLoop CurrentLoop Current


Off-HookOff-Hook GroundGroundGroundGround


Off-HookOff-Hook GroundGroundGroundGround


Sending Switch Receiving Switch

Wink

On-Hook Off-HookReceiving Switch Goes Momentarily Off-Hook for 140 to 200 msec

DTMF DigitsSending Switch Waits a Minimum of 210 msec Before Sending Addressing

On-HookOff-Hook

Receiving Switch Goes Off-Hook After Connection Is Established

Off-HookOn-Hook

Sending Switch Goes Off-Hook

I’m Ready to Receive theI’m Ready to Receive theNumber Now—Wink StartNumber Now—Wink Start

11



Sending Switch Receiving Switch

DTMF DigitsSending Switch Waits a Minimum of 150 msec Before Sending Addressing

On-HookOff-Hook

Receiving Switch Goes Off-Hook After Connection Is Established

Off-HookOn-Hook

Sending Switch Goes Off-Hook

I’m Always Ready to Receive—I’m Always Ready to Receive—Immediate StartImmediate Start


E&ME&M E&ME&M

PBXPBXSwitchSwitch

E&M Signaling and Wink StartE&M Signaling and Wink Startor Immediate Startor Immediate Start

• The only caveat—make sure yoursignaling type matches up withyour PBX

12



EMEM

EMEM

EMEM

EMEMTie Trunks

CO TrunksCO Trunks

Tie Trunks

Primary Trunk Signaling MethodPrimary Trunk Signaling Method

• PBX to local exchange office (telephone company)

• CO trunks

• Direct inward dial (DID) trunks

• Direct outward dial (DOD) trunks

• PBX to PBX connections

• Tie trunks

PBXPBX

PBXPBX

SwitchSwitch


Voice Evolution:Voice Evolution:The Formative YearsThe Formative Years

13



Distorted AnalogCommunications

Clear DigitalCommunications

300–3400 Hz @ 4 KHz2 x 4 KHz = 8 KHz

8 KHz x 8 Bits = 64 kbps

Digital Signaling—Digital Signaling—Better and CheaperBetter and Cheaper


Extended Super Frame

Time Slot #X

1 7 81

6

12

18

24

A

B

C

D

Time Slot #24

1 7 81

6

12

18

24

Usabl

e fo

r ISD

N or P

BX Si

gnal

ing

Usabl

e fo

r ISD

N or P

BX Si

gnal

ing

Channel Associated Signaling (CAS)or Robbed Bit Signaling

Common Channel Signaling

T1 Signaling FormatT1 Signaling Format

14



01 2 8

1

23456

10

15

78

9

111213

14

Semi-Multiframe (SMF) 1

Semi-Multiframe (SMF) 2

3 4 5 6 70 0 0 X X X X0

A B C D1

A B C D2A B C D3

A B C D4

A B C D8

A B C D5

A B C D9

A B C D12

A B C D7

A B C D6

A B C D10

A B C D11

A B C D13

A B C D14A B C D14

A B C D17

A B C D18A B C D19

A B C D20

A B C D24

A B C D21

A B C D25

A B C D28

A B C D23

A B C D22

A B C D26

A B C D27

A B C D29

A B C D30A B C D31

Time Slot #16

1 2 8

1

23456

10

15

789

11121314

3 4 5 6 70

Time Slot #16

Usabl

e fo

r ISD

N or P

BX Si

gnal

ing

Channel Associated Signaling Common Channel Signaling

E1 CAS Signal FormatE1 CAS Signal Format


Loop Start Signaling

TelephoneNetwork

2 Wire T1 Leased Line

T1 Robbed Bit SignalingUsing E&M, A and B Bits = 0,

Off-Hook

PBXPBX

CO SwitchCO SwitchCO SwitchCO Switch

Sample CallSample Call

15



Voice Evolution:Voice Evolution:Dawn of the Digital AgeDawn of the Digital Age

Touch Tone Phones

Faxes

Wow! This Is Better than Fire


The Advanced Intelligent NetworkThe Advanced Intelligent Network

• More efficient

• Support real-time operations oftelephone network’s capabilities

• Supports transport transparency

• Customer can create newapplications and is providedgreater control

16



TelephoneNetwork

BRI BRI

PRI PRI

SupplementaryServices

Scope of Bearer Services

Scope of Teleservices

SupplementaryServices

Basic Rate Interface (BRI) (2B + D)Primary Rate Interface (PRI) (23B + D or 30 B + D)

PBX1PBX1 SwitchSwitchSwitchSwitch PBX2

PBX2

Public N-ISDN IntelligentPublic N-ISDN IntelligentAccess to the NetworkAccess to the Network


Functional Devices andFunctional Devices andReference PointsReference Points

TerminalAdapter

(TA)

Non-ISDNTerminal

Equipment(TE2)

R S/T

ISDNTerminal

Equipment(TE1)

CustomerPremisesSwitchingEquipment

(NT2)

Local LoopTerminator

(NT1)

ISDN LocalExchange

(LE)

S T U

Network Boundary per ITU-T Network Boundary in U.S.(No ITU-T Standard)

Standard per TAManufacturer

17



ApplicationApplication

I.430 Basic Interface + I.431 Primary InterfaceI.430 Basic Interface + I.431 Primary Interface

LAPDLAPD LAPBLAPBI.465/V.120I.465/V.120

X.25X.25X.25X.25FurtherStudy

FurtherStudy

End-to-EndUser

Signaling

End-to-EndUser

Signaling

ControlSignalingControl

SignalingPacketPacket TelemetryTelemetry Circuit

SwitchCircuitSwitch

Semi-Permanent

Semi-Permanent

PacketSwitchedPacket

Switched

D ChannelD Channel B ChannelB Channel

PresentationPresentation

SessionSession

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

I.45XCall Control

I.451 = Q.931 Basic Call ControlI.452 = Q.932 Supplementary Services

ISDN Protocol StackISDN Protocol Stack


Protocol Discriminator (Q.931)Protocol Discriminator (Q.931)

Length of CRVLength of CRV

Call Reference Value

(1 or 2 bytes)

Call Reference Value

(1 or 2 bytes)

BitsOctet

8 7 6 5 4 3 2 1

0 0 0 0 1 0 0 00 0 0 0 1 0 0 0

0 0 0 00 0 0 0

CR Flag

0 Message TypeMessage Type

0/1 Information Element IdentifierInformation Element Identifier

Length Information Element IdentifierLength Information Element Identifier

Contents of Information ElementContents of Information Element

Next Information Element, etcNext Information Element, etc

1

2

3

1

2

3 or 4

4 or 5

Q.931/932 Message FormatQ.931/932 Message Format

• Call reference—establishes a uniquevalue between userand the network

• Message type—canbe grouped into callestablishment, callinfo phase, call clearingand misc.

• Information elements—areself contained entities thatfurther define the message

18



Supplementary ServicesSupplementary Services

• Types:Number identification, call offering, call completion,multiparty, community of interest, charging,additional information transfer

• Control and invocation, three genericprotocols:

Keypad—uses the keypad and displayinformation elements

Feature key—uses the feature activation and featureindication information elements

Functional protocol—facility message and facilityInformation element or specific messages like HOLD


CallingParty

Network

Setup

Setup Acknowledge

Information

Call ProceedingSetup

Call Proceeding

AlertingAlerting ConnectConnect

Connect AcknowledgeConnect Acknowledge

CalledParty

Q.931/Q.932 Call CompletionQ.931/Q.932 Call Completion

19



SignalingNetwork

TelephoneNetwork

SwitchSwitch PBX2PBX2SwitchSwitchPBX1

PBX1

The Intelligent NetworkThe Intelligent Network


SSPSSPSSPSSP

STPSTP

SCPSCP

STPSTP

STPSTP STPSTP

SS7 Local ArchitectureSS7 Local Architecture

• Service control point—database information

A or access links—access to STPs

• Signal transfer point—routing of SS7 packets

B or bridge links—connect STPsat the same level

C or cross links—connect matedpairs of STPs, B and C links togethermake up a quad

A or access links—access to STPs

• Service switching point—access switches or their proxy

SCPSCP

20



SCPSCP SCPSCPSCPSCP SCPSCP

Local Regional

D or Diagonal Links for Connecting a Local STP Pair to a Regional STP Pair

E or Extended Links Used to ConnectSSPs to a Secondary Pair of Mated STPs

F or Fully Extended Links Directly Interconnect Two SS7 Switches

STPSTP STPSTP

STPSTP STPSTP

SSPSSP

STPSTP STPSTP

STPSTP STPSTP

SSPSSP SSPSSP SSPSSP

SS7 Connection toSS7 Connection toRemote NetworkRemote Network


ISDN UserPart (ISUP)ISDN UserPart (ISUP)

Circuit-Related Services

TCAPTCAP

ASEASEOMAP

Non-Circuit ApplicationsNon-Circuit Applications

MTPLevel 1

Level 2

Level 3

NullNull Presentation, Session, Transport

Presentation, Session, Transport


OMAP - Oper., Maint. and Admin. Part MTP - Message Transfer PartASE - Application Service Element TCAP - Transaction Capabilities Application PartISUP - ISDN User Part TUP - Telephone User PartDUP - Data User Part SCCP - Signaling Connection Control Part

OSI Reference Model

Network Message Handling, Network Management

Signal LinkSignal Link Bit Oriented ProtocolBit Oriented Protocol

Signal Data Link Speeds up to 64 kbps

TUP(ITU)TUP(ITU)

DUP(ITU)

Network

Data LinkData LinkPhysical

SS7 Protocol StackSS7 Protocol Stack

SCCPSpecialized Routing

21



ISUPTCAP

SCCP

MTP

NullNull

MTP L3

MTPL2MTPL2MTPL1

SCCP

MTP

MTP L3

MTPL2MTPL2MTPL1

SCCP

MTP

MTP L3

MTPL2MTPL2MTPL1

SCCP

MTP

MTP L3MTPL2MTPL2MTPL1

SCCP

MTP

MTP L3MTPL2MTPL2MTPL1

TCAP

SCCP

MTP

NullNull

MTP L3

MTPL2MTPL2MTPL1

ISUPTCAP

SCCP

MTP

NullNull

MTP L3

MTPL2MTPL2MTPL1

Protocol Usage—Protocol Usage—Network ElementsNetwork Elements

STPSTP

STPSTP

STPSTP

STPSTP

SSPSSP SSPSSP

SCPSCP


BSN/BIBB—Backward Sequence Number/Backward Indicator BitFSN/FIB—Forward Sequence Number/Forward Indicator BitLength—0=FISU, 1 or 2 = LSSU, 3 or greater = MSUSIO—Service Information Octet, Type of Protocol and StandardSIF—Service Information Field, Transfer Control InformationFCS —Frame Check Sequence

Fill-In Signal Unit (FISU)

Link Status Signal Unit (LSSU)

Message Signal Unit (MSU) Up to 272 bytes in Length

1-2 Bytes (Always 1)

FLAGBSN/BIBFSN/FIBLengthFCS 00

FLAGBSN/BIBFSN/FIBLengthFCS 00SIFSIF SIOSIO1 byte

FLAGBSN/BIBFSN/FIBLengthFCS StatusStatus 00

variable

MTP Messages (Level 2 and 3)MTP Messages (Level 2 and 3)

22



FLAGBSN/BIBFSN/FIBLengthFCS 0 0SIF SIO

Varies by Protocol/Function Routing Label

DestinationPoint Code

OriginationPoint CodeSLS

SLS = Signaling Link Selection Code

24 Bits24 Bits8 bits (5 Used)14 Bits14 Bits4 Bits

ANSIITU

or

Message Signal Units (MSUs)Message Signal Units (MSUs)

• Message discrimination—looks at the point code in the routinglabel to determine if the message is local

• Message distribution (message is local)—uses the SIO todetermine the user (application) part

• Message routing (message is not local)—attaches a new routinglabel and determines the proper link for next signal point

SLS OriginationPoint Code

DestinationPoint Code


ISDN User Part (ISUP)ISDN User Part (ISUP)

• ISUP is used to set up and teardown all circuits used in the PSTN,Telephone User Part (TUP) is usedinternationally as well

• Support for non-voice calls andsupplementary services withend-to-end significance

23



Message Type ( 1 Octet )

Mandatory Fixed Parts

Mandatory Variable Parts

Optional Parts

Sample Message Types

Initial Address Message (IAM)

Address Complete (ACM)

Answer (ANM)

Continuity (COT)

52 message types (ANSI, Bellcore & ITU)

Circuit Identification Code

2 Spare bits


Signaling Info CIC

14 Bits14 Bits

ISDN User Part (ISUP)ISDN User Part (ISUP)

Routing Label


TE STPSSP TESSP

Q.931 Q.931SS7

Setup

CallProceeding

IAMIAM

SetupCall

Proceeding

AlertingACM

ACMAlerting

Connect

ConnectANM

ANM

B Channel B ChannelTrunk Trunk

ReleaseComplete Release

Complete

DisconnectDisconnect

RELREL

RLCRLC

ReleaseRelease

ISUP Call FlowISUP Call Flow

24



Signaling Connection ControlSignaling Connection ControlPart (SCCP)Part (SCCP)

• Larger more complete address spacesupplements MTP addressing byadding called party and calling partynumbers (subsystem numbers—SSNs)

• Protocol used for accessing databasesand other network entities (i.e. TCAP)

• Global title translation


Routing LabelSCCPxxxx 0011

TCAP

Message Type

Mandatory Fixed Parts

Mandatory Variable Parts

Optional Parts


Signaling Connection ControlSignaling Connection ControlPart (SCCP) Message FormatPart (SCCP) Message Format

25



Transaction CapabilitiesTransaction CapabilitiesApplication Part (TCAP)Application Part (TCAP)

• General purpose remote operationfunction for SS7

• Originally designed to supportdatabase queries, such as callingcards and 800 numbers


Transaction Portion (Nature of the Message)

Invoke Component

Parameter Set Sequence


Routing LabelSCCPxxxx 0011

TCAP

TCAP Message FormatTCAP Message Format

26



TCAP Call FlowTCAP Call Flow

TE STPSSP SCP

Q.931

Setup

SS7

SetupAcknowledge

Information

Begin

Continue

Begin

Continue

Play Announcement and Collect Digits

ContinueContinue

EndEnd

Pass Collected Digits

Call Proceeding

Actual Network AddressIAM


AIN LimitationsAIN Limitations

• Sporadic deployment

• Poor consistency

Lack of interoperability between vendorsand between service providers

• Master slave relationship

• Intelligence resides in the network

27



These 900 Numbers, WhatWill They Think of Next

Voice Evolution:Voice Evolution:AIN ServicesAIN Services


PSS1 PSS1

PSS1

PISNPISN

PINX—Private Integrated Services Network Exchange

PISN—Private Integrated Services Network

PSS1—Private Signaling System 1 (QSIG)

Private N-ISDN (QSIG)Private N-ISDN (QSIG)

• Purpose: To extend facilities normally only availablebetween extensions on a single PBX to all extensions onPBX’s that are connected together in a Private Network

PINX2PINX2

PSTNPSTN

PINX4PINX4

PSTNPSTNPINX1PINX1

PSTNPSTN

28



QSIG BenefitsQSIG Benefits

• Multivendor ISDN PBX-based network

• Networking of remote ISDN PBX’s

• Interconnecting voice/fax and DP servers

• Network wide applications

• Support mobility


PINXX

Q

TE

S

N

Public ISDN A Public ISDN B

S/T

PINXY

Q

PINXZ

QNetwork, e.g. Leased Line

TE TE TE TE

S S/T S/T S

TT

C C C

QSIG Reference PointsQSIG Reference Points

• PINX—Private Integrated ServicesNetwork Exchange

29



QSIG ProtocolQSIG Protocol

ROSE: Remote Operation Service ElementsACSE: Association Control Service ElementsNetwork Specific

ROSE: Remote Operation Service ElementsACSE: Association Control Service ElementsNetwork Specific

End-to-End ProtocolNetwork TransparentEnd-to-End ProtocolNetwork Transparent

Basic RateI.430Basic RateI.430

Primary RateI.431Primary RateI.431

CopperCopper CopperCopper OpticalOptical

InterfaceDependentProtocols

InterfaceDependentProtocols

MediaMedia

PhysicalPhysical

Link LayerLink Layer

NetworkNetwork

Layer 4–7Layer 4–7

Supplementary Services and ANFsSupplementary Services and ANFs

ECMA 148, 157, 163, 164, 173-178, 185, 186, 191-194, 202, 203, 211-214, 220, 221, 224, 225, 241, 242, 250,251, 263, 264

ECMA 148, 157, 163, 164, 173-178, 185, 186, 191-194, 202, 203, 211-214, 220, 221, 224, 225, 241, 242, 250,251, 263, 264

ISO 11582, ETS300 239 ECMA156, 161, 165ISO 11582, ETS300 239 ECMA156, 161, 165

ISO 11574, ETS300 171/172/173, ECMA 106, 142, 143ISO 11574, ETS300 171/172/173, ECMA 106, 142, 143

LAPD, ETS300 402LAPD, ETS300 402

QSIG GenericFunctional ProceduresQSIG GenericFunctional Procedures

QSIG Basic CallQSIG Basic Call


PINX X PINX YSetup

Setup

Call Proceeding

Call Proceeding

Alerting

AlertingConnect

Connect

Connect Acknowledge

Connect Acknowledge

PINX Z

Terminal Node Transit Node Terminal Node

Basic Call CompletionBasic Call Completion

30



QSIG Generic Functional ProceduresQSIG Generic Functional Procedures

PHYPHY

DLCDLC

Protocol ControlProtocol Control

Generic FunctionalTransport


PHYPHY

DLCDLC




PHYPHY

DLCDLC




Transit PBX

ROSE—Remote Operation Service Element

ACSE—Association Control Service Element

DSE—Dialog Service Element

Service ElementService Element

SS Control 1SS Control 1

......SS Control nSS Control n


Coo

rdin

atio

nFu

nctio

nC

oord

inat

ion

Func

tion

End PBX

Service ElementService Element

SS Control 1SS Control 1

......SS Control nSS Control n


Coo

rdin

atio

nFu

nctio

nC

oord

inat

ion

Func

tion

End PBX


Voice Evolution:Voice Evolution:A Better Private NetworkA Better Private Network

31



Why Packet-Based Telephony?Why Packet-Based Telephony?

• Data networks are growing at a fasterrate then voice networks

• One network is cheaper and easierto manage then two

• Leverage the flexibility inherent indata networks for voice


H.323H.323

• International (ITU) standard for:Packet-based multimediacommunications systems

• Version 1 established in 1996, Version 2in 1998 and Version 3 in the works

• Refer to various annexes for more details

• Leverages previous developments withinITU (i.e. Q.931)

32



LAN A

H.323 H.323

RouterLAN B

H.323 H.323

H.323 TerminalH.323 Terminal

• Multimedia communications servicesover packet-based networks

• Real-time audio, video and/ordata communication

• Point-to-point, multipoint, or broadcast


LAN A

H.323 H.323

Gateways H.320(Over ISDN)

H.324(Over POTS)

Speech Only(Telephone)

H.323 GatewaysH.323 Gateways

• Appropriate translation betweentransmission formats

• Translation betweencommunication procedures

• Call setup and clearing on both sides

TelephoneNetwork

33



LAN A

H.323

H.323

Gateways

H.320(Over ISDN)

H.324(Over POTS)


Gatekeeper

Router

LAN BZONE

TelephoneNetwork

H.323 GatekeeperH.323 Gatekeeper

Intranet


H.323 GatekeeperH.323 Gatekeeper

• Optional

• Required featuresAddress translation (alias to transport within zone)

Admissions control (maybe null)

Bandwidth control during the call (maybe null)

• Optional featuresCall control signaling/routing (under GK control)

Call authorization

Call management (call status, tracking, PBX-likeservices etc.)

34



LAN A

H.323 H.323

GatewaysH.320(Over ISDN)

H.324(Over POTS)


Gatekeeper

Router

LAN BZONE

MCU

H.323 Multipoint Control UnitH.323 Multipoint Control Unit(MCU)(MCU)

TelephoneNetwork

Intranet


H.323 Terminal—MultipointH.323 Terminal—MultipointControl Unit (MCU)Control Unit (MCU)

• An endpoint which provides supportfor multipoint conferences

• A MCU consists of a multipointcontroller (MC) and one or moremultipoint processors (MP)

• Endpoints establish a point to pointconnection with the MC

• Actual video or audio distributionmaybe centralized or distributed

35



Delay

Video CodecH.261, H.263

Call ControlH.225.0

System Control

ReceivePath

Audio CodecG.711, G.722,G.723, G.728,

G.729

RAS ControlH.225.0

RTP

RTCP(sync)

H.225Layer

UDP

TCPH.245 Control

Audio I/O equipment

User Data Applications

T.120, etc.

System ControlUser Interface

Video I/O equipment

UDP

IP

Scope of H.323 RecommendationScope of H.323 Recommendation


H.323 CallingParty

H.323 CalledParty

Setup—H.225 Call Signaling Channel

• Setup message to called party’swell known call signalingchannel identifier

H.225

H.245 Control Channel • Capabilities exchange and

master/slave determinationover reliable channel

H.245 H.245 Logical Channel Setup (RTP)

H.245 Logical Channel Setup (RTCP)

H.245 Logical Channel Setup (RTP)

H.245 Logical Channel Setup (RTCP)

• Logical channels setup overunreliable channels formultimedia streams

Call Proceeding

Alerting

Connect• Connect message contains

H.245 control channel transportaddress for H.245 signaling

Call Signaling Procedures—Call Signaling Procedures—No GatekeeperNo Gatekeeper

36



H.450 Supplementary ServicesH.450 Supplementary Services

• H.450-1 Generic Functional Protocol

• H.450-2 Call TransferSupplementary Services

• H.450-3 Call DiversionSupplementary Services


H.323 LimitationsH.323 Limitations

• Relatively slow—due to the extensiveamount of message exchange

• Designed with peer to peermultimedia communications in mind

• Protocol format has some limitations

37



I Guess I BetterReboot My Phone

Voice Evolution: End of theVoice Evolution: End of theIntelligent Network?Intelligent Network?


Session Initiation Protocol (SIP)Session Initiation Protocol (SIP)

• Internet telephony not telephonyover Internet

• Currently underdevelopment withinthe IETF (multiparty multimediasession control working group)

38



User Agents

Client

Server

Redirect

Client

Server

User Agents

Proxy

IP BasedNetwork

Clie

nt

Se

rv

er

IP-BasedNetworkInvite

Invite

SIP Architecture:SIP Architecture:Contacting the ProxyContacting the Proxy


User Agents

Client

Server

Redirect

Client

Server

User Agents

Proxy

IP BasedNetwork

Clie

nt

Se

rv

er

IP-BasedNetworkResponse OK

Response OK

SIP Architecture:SIP Architecture:Proxy Responding to ClientProxy Responding to Client

39



User Agents

Client

Server

Redirect

Client

Server

User Agents

Proxy

IP-BasedNetwork

Clie

nt

Se

rv

er

Ack

Ack

SIP Architecture:SIP Architecture:Client AcknowledgementClient Acknowledgement


User Agents

Client

Server

Redirect IP-BasedNetwork

Client

Server

User Agents

Proxy

Invite

Ack

Contact

SIP Architecture:SIP Architecture:Contacting the Redirect ServerContacting the Redirect Server

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User Agents

Client

Server

Redirect IP-BasedNetwork

Client

Server

User Agents

Proxy

Invite

Ack

SIP Architecture:SIP Architecture:Contacting the UserContacting the User

Response


SIP ProtocolSIP Protocol

• SIP addressing takes the formof a mail to URL (i.e. user@host,examples sip:[email protected])

• Session Description Protocol (SDP)is used to form the message,analogous to Q.931 messagesand information elements

• Modeled around HTTP, but with UDP

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SDP Media

H.323 RTSP SIP RTCP RTP RSVP

TCP UDP

IP

Internet Telephony ProtocolsInternet Telephony Protocols


SIP vs. H.323SIP vs. H.323

• SIP uses text for encoding ofmessages. H.323 uses ASN.1

• SIP uses a single request to sendall necessary information

• UDP based. Recent changes byH.323 will allow utilization of UDPas well

• H.323 has widespread usage

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•picture of alien

Internet Telephony Evolution:Internet Telephony Evolution:Alien Life Form?Alien Life Form?


Gateway Control ProtocolsGateway Control Protocols

• Allows remote control of various devices

• Create, modify, and delete connections.Generates and detect events (tones).Tracks resource states.

• Fits in well with multimedia call signaling(i.e. H.323 and SIP)

• Strong support for existingtelephone networks

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SGCP(IETF)

IPDC

MGCP 1.0(IETF)

MDCP(IETF)

MEGACO(MGCP+)

(IETF)

October ’98

December ’98Lucent

August ’98Level 3

July ‘98BellcoreCisco

April ’99

Gateway Control MigrationGateway Control Migration

• SGCP—Simple GatewayControl Protocol

• IPDC—IP Device Control

• MGCP—Media GatewayControl Protocol

• MDCP—Media DeviceControl Protocol

• MEGACO—Media GatewayController


SignalingGateway

MediaGateway

Controller

MediaGateway

Controller

SS7Network

SS7Network

PSTNNetwork

PSTNNetwork

H.323 or SIP

H.323+, SIP+, ISUP+

MGCP, H.GCP Megaco

Sigtran Sigtran

MGCP, H.GCP Megaco

MediaGateway

SignalingGateway

MediaGateway

GCP Protocol RelationshipGCP Protocol Relationship

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MGCPMGCP

• Retains SGCP simplicity

• Uses established standards (SDP)

• Additional SDP functions for other network types IP, ATM

• Uses IPDC features Wildcards

Event grouping

Control extensions

Endpoint audit

Connection audit

Restart


GWGW11

CallCallAgentAgent

IP Cloud

Notification

ModificationCreation

Signaling Between Call Agent and Gateway

Notification

Signaling Between Gateway and Call Agent

MGCP Call AgentMGCP Call Agent

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GWGW11

CallCallAgentAgent

IP Cloud

Monitor

Q StateQ State

GWGW22

Analog Call Using MGCPAnalog Call Using MGCP

Calling Session

11

Dialed Digits

22

55

33

Called Session

44

RTP Connection

66


Dialed Digits

COCO

Dialed Digits to CO Start the Call

SSP

SSP SSP

CallCallAgentAgent

TGWTGW11 TGWTGW22

IP Cloud

MonitorSS7/ISUP

Q StateQ State

COCO

STPSTP STPSTP

11 22

Calling Session

3344

66

Called Session

55

RTP Connection

77

MGCP and SS7 InteroperabilityMGCP and SS7 Interoperability

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SummarySummary

• Call signaling has taken an evolutionarypath. The underlying core is to providebasic call control. The next step isunderstanding how new services areadded (supplementary services)

Please Complete YourPlease Complete YourEvaluation FormEvaluation Form

Session 408Session 408


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Documents

CISCO -- Introduction to Voice Over IP and Other Integrated Services -- Session 408 - (2000)