3333

SoftswitchSoftswitchSoftswitch Softswitch A hit tA hit tArchitectureArchitectureInternational Softswitch International Softswitch

C ti (ISC) R fC ti (ISC) R fConsortium (ISC) ReferenceConsortium (ISC) Reference

SoftswitchSoftswitch Defining and Relationship to NGNNGNSource : Study on Application of Softswitch in Wireless NetworkStudy on Application of Softswitch in Wireless NetworkSource : Study on Application of Softswitch in Wireless NetworkStudy on Application of Softswitch in Wireless Network

page 128

F ti l PlF ti l PlISC Reference Softswitch ArchitectureISC Reference Softswitch ArchitectureFunctional PlaneFunctional Plane

Service & Application Plane

Application/Feature Server(SCP, Service Logic, LDAP Server)

ManagementPlane IN/AIN

Open APIs & Protocols (JAIN, Parlay, XML, SIP)

alin

g (S

IP)

Call Agent, MGC, Softswitch, GK Inter-NetworkSwitch

Subscriber &ServiceProvisioning,Network Signaling (MGCP, H.248, SIP)A

pplic

atio

n Si

gna

SIP-T; H.323Call Control & Signaling Plane

Transport Plane

IP Transport Domain:IP Backbone, Routers, Switches, BGsQoS Mechanism (RSVP, Diffserve,MPLS...), MS (Bearer Portion)

InterworkingDomain:TG (MG), SG,InterworkingGateway

MediaServer

PSTN/SS7/ATMNetworks

Management,OperationSupport, BillingSupport

g g ( , , )A

), ( ) Gateway

Non-IP Access Domain:Wireline Access (AG, Access Proxies)Mobile Access (RAN AG)Broadband Access (IADs, MTAs)

other VoIPNetworks

Broadband Access (IADs, MTAs)

Non-IP Terminals/Mobile Networks

IP Phones (H.323, SIP,MGCP, ...),IP Terminals,IP PBX

1. Transport Plane1. Transport Plane• Responsible transport of messages (call signaling, call and media

th V IP t ksetup, or media) across the VoIP network.• Transport mechanism(s) for these messages based on any technology that satisfies

the requirements for carrying these types of traffic.Provides access for signaling and media with external• Provides access for signaling and media with external networks, or terminals to VoIP networks.

• Transport Plane devices and functions are controlled by Call Control & Signaling PlanePlane.

• The transport plane is further divided into three domains:• IP Transport Domain :

Inter orking Domain• Interworking Domain;• Non-IP Access Domain

a. IP Transport Domaina. IP Transport Domain• Provides the transport backbone and routing/ switching

fabric for transporting packets across the VoIP network.Devices like routers and switches belong to this domain Devices that provideDevices like routers and switches belong to this domain. Devices that provide Quality of Service (QoS) mechanisms and policies for the transport also belong to this domain.

b. Interworking Domainb. Interworking Domain• Domain are primarily responsible for the transformation of

signaling or media received from external networks into a formsignaling or media received from external networks into a form that can be sent among the various entities in the VoIP network and vice versa.

• Consists of devices like :•• Signaling GatewaysSignaling Gateways (signaling transport conversion between different

transport layers),•• Media GatewaysMedia Gateways (media conversion between different transport networks

and/or different media),•• Interworking GatewaysInterworking Gateways (signaling interworking on the same transport g yg y ( g g g p

layer but with different protocols).

c. Nonc. Non--IP Access DomainIP Access Domain• Domain that applies to non-IP terminals and wireless radio

networks that access the VoIP network.• Consists of :• Consists of :

•• Access GatewaysAccess Gateways or Residential GatewaysResidential Gateways for non-IP terminals or phones.

• ISDN terminals,• Integrated Access Devices (IADs) for DSL

networksnetworks,• Cable Modem/Multimedia Terminal Adaptors

(MTAs) for HFC networks, andM di G t f GSM/3G bil di• Media Gateways for a GSM/3G mobile radio access network (RAN).

Note : that the IP terminals, like a SIP phone, will directly connect to the IP Transport Domain, without going through an Access Gateway.

2 Call Control & Signaling Plane2 Call Control & Signaling Plane2. Call Control & Signaling Plane2. Call Control & Signaling Plane• It controls the major elements of the VoIP network,

especially in the Transport Plane.• Carry out call control based on signaling messages received

from the Transport Plane, handle establishment and teardown of media connections across the VoIP network by ycontrolling components in the Transport Plane.

• Consists of devices like :• Media Gateway Controller (a.k.a. Call Agent or Call

Controller)Controller),• Gatekeepers and• LDAP servers.

3. Service & Application Plane3. Service & Application Plane• Provides the control, logic and execution of one or more , g

services or applications in a VoIP network.• Control the flow of a call based on the service execution logic.

They achieve this by communication with devices in the CallThey achieve this by communication with devices in the Call Control & Signaling Plane.

• Service & App Plane consists of devices like :A li ti S d• Application Servers and

• Feature Servers.Service & App Plane may control specialized bearer components, such asppMedia Servers, that perform functions like conferencing, IVR, tone processing,

and so on.

4. Management Plane4. Management PlaneIt functions such as :

S b ib d i i i i• Subscriber and service provisioning,• Operational support,• Billing andg• Other network management tasks are handled.

It can interact with any or all of the other three planes through industry standard (e g SNMP) or proprietary protocols and APIsindustry standard (e.g. SNMP) or proprietary protocols and APIs.

Functional Entities

The diagram above shows 12 different functions. Understanding the autonomy of all 12 functions is an important characteristic of the ISC Reference Architecture.

1).1). Media Gateway Controller FunctionMedia Gateway Controller Function(MGC(MGC--F) a k a Call Agent or Call ControllerF) a k a Call Agent or Call Controller(MGC(MGC F) a.k.a. Call Agent or Call ControllerF) a.k.a. Call Agent or Call Controller

Provides the call state machine for endpoints. Its primary role is to provide the call logic and call control signaling for one or more

di tmedia gateways.• Maintains call state for every call on a media gateway• May maintain bearer states for bearer interfaces on the y

MG-F• Communicates bearer messages between two MG-Fs, as

well as with IP phones or terminalswell as with IP phones or terminals• Acts as conduit for media parameter negotiation• Originates/terminates signaling messages from endpoints,

th MGC F d t l t kother MGC-Fs and external networks• May interact with the AS-F for the purposes of providing a

service or feature to the user• May manage some network resources (e.g. MG-F ports,

bandwidth etc.)

• May provide policy functions for endpoints• Interfaces to R-F/A-F for call routing, authentication and

accountingaccounting• May participate in management tasks in a mobile environment

(mobility management is generally part of the CA-F)A li bl t l i l d H 248 d MGCP• Applicable protocols include H.248 and MGCP

2). Call Agent Function (CA-F) and 3) Interworking F i (IW F)Function (IW-F)

CA-F and IW-F are subsets of the MGC-F.• CA-F exists when the MGC-F handles call control and callCA F exists when the MGC F handles call control and call

state maintenance. Examples of CA-F protocols and APIs include :• SIP, SIP-T, BICC, H.323, Q.931, Q.SIG, INAP, ISUP, TCAP, BSSAP,

RANAP MAP and CAP (mobile)RANAP, MAP and CAP (mobile)• Open APIs (JAIN, Parlay, etc.)

• IW-F exists when the MGC-F performs signaling interaction between different signaling networks (e g SS7 and SIP)between different signaling networks (e.g. SS7 and SIP). Examples of IW-F protocols include H.323/SIP

4).4). Call Routing and Call Routing and 5).5). Accounting Functions (RAccounting Functions (R--F/AF/A--F)F)))• R-F provides call routing information to the MGC-F, while the• A-F :

• collects call accounting information for billing purposes• collects call accounting information for billing purposes. A-F can also

• have a broader role embodied by the common AAA functionality (authentication authorization andfunctionality (authentication, authorization and accounting) in remote access networks.

Primary role of both functions is to respond to requests from one or more MGC-Fs, directing the call or its accounting to terminating endpoints (other MGC-Fs) or services (AS-Fs)p ( ) ( )

R-F/A-F Characteristics :• Provides routing function for intra- and inter-network call

routing (R F)routing (R-F)• Produces details of each session for billing and planning

purposes (A-F)• Provides session management and mobility management• May learn routing information from external sources• May interact with the AS-F for the purposes of providing aMay interact with the AS F for the purposes of providing a

service or feature to the user• May operate transparently to the other entities in the signaling

pathpath• Many R-Fs and A-Fs can be chained together in a sequential

or hierarchical manner• The R-F/A-F is often integrated with the MGC-F. However, just

as is the case with the ASF,• An integrated R-F/A-F/MGC-F can also request services of anAn integrated R F/A F/MGC F can also request services of an

external R-F/A-F.

• The A-F collects and emits per-call accounting information. The AS-F emits accounting information for enhanced services such as conferences and premium informationservices, such as conferences and premium information services.

• Applicable protocols for the R-F include ENUM and TRIPA li bl t l f th A F i l d RADIUS d A C• Applicable protocols for the A-F include RADIUS and AuC(for mobile networks)

6). SIP Proxy Server Function (SPS-F)The most common embodiment of the R-F and A-F is as a SIP P S F thi th ISC i t SIPProxy Server. For this reason, the ISC recognizes a separate SIP Proxy Server Function (SPS-F).

7).7). Signaling Gateway Function (SGSignaling Gateway Function (SG--F) andF) and8).8). AccessGatewaySignaling Function (AGSAccessGatewaySignaling Function (AGS--F)F))) y g g (y g g ( ))• SG-F provides a gateway for signaling between a VoIP

network and the PSTN, whether SS7/TDM- or BICC/ATM-based For wireless mobile networks the SG-F also provides abased. For wireless mobile networks, the SG-F also provides a gateway for signaling between an IP-based mobile core network and PLMN that is based on either SS7/TDM or BICC/ATMBICC/ATM.The primary role of the SG-F is to encapsulate and transport PSTN (ISUP or INAP) or PLMN (MAP or CAP) signaling ( ) ( ) g gprotocols over IP.

• AGS-F provides a gateway for signaling between a VoIP network and circuit-switched access network whether V5- ornetwork and circuit-switched access network, whether V5- or ISDN-based.

• For wireless mobile networks, the AGS-F also provides a t f i li b t IP b d bilgateway for signaling between an IP-based mobile core

network and PLMN that is based on either TDM or ATM.

AS-F Characteristics:• May request the MGC-F to terminate calls/sessions for certain

applications (e g voice mail or conference bridge)applications (e.g. voice mail or conference bridge)• May request the MGC-F to re-initiate call features (e.g. find

me/follow me or pre-paid calling card)• May modify media descriptions using SDP• May modify media descriptions using SDP• May control an MS-F for media handling functions• May be linked to Web applications or have Web interfaces

M h API f i ti• May have an API for service creation• May have policy, billing and session log back-end interfaces• May interface with MGC-Fs or MS-Fs

M i k th AS F f dditi l i t b ild l• May invoke another AS-F for additional services or to build complex, component-oriented applications

• May use the services of an MGC-F to control external resourcesS GC C• Applicable protocols include SIP, MGCP, H.248, LDAP, HTTP, CPL

and XML• Applicable open APIs include JAIN and ParlayNote : Often the combination of the AS-F and the MGC-F provides enhanced call control services, such as network announcements, 3-way calling, call waiting and so on. Rather than connecting the AS-F and MGC-F with a protocol, vendors often use an API between the AS-F and MGC-F when they are implemented in a single system. In this embodiment, the AS-F is known as a “Feature Server.”

AGS-F Characteristics :• Encapsulates and transports V5 or ISDN signaling protocols

( SS7) i The interface from the AGS F to the other(e.g. SS7) using The interface from the AGS-F to the other entities is a protocol interface when the AGF-F and MGC-F or other AGF-F are not co-located (e.g. SIGTRAN)

• SIGTRAN to the MGC-F• For mobile networks, encapsulates & transports BSSAP or

RANAP signaling protocols (e.g. SS7) using SIGTRAN to the MGC-F• One MGC-F may serve many AGS-Fs• Applicable protocols include SIGTRAN, M3UA, IUA and

V5UA over SCTPV5UA over SCTP

9).9). Application Server Function (ASApplication Server Function (AS--F)F)The AS-F is the application execution entity. Its primary role is to provide the service logic and execution for one or more applications and/or servicesapplications and/or services.

The primary role of the AGS-F is to encapsulate and transport V5 or ISDN (wireline), or BSSAP or RANAP (wireless) signaling protocols over IPprotocols over IP.

RR--F/AF/A--F Characteristics :F Characteristics :• Encapsulates and transports PSTN signaling protocols (e.g.

SS7) using SIGTRAN to the MGC-F or another SG-F• For mobile networks, encapsulates and transports PSTN/For mobile networks, encapsulates and transports PSTN/

PLMN signaling protocols (e.g. SS7) using SIGTRAN to the MGC-F or another SG-F

• The interface from the SG F to the other entities is a protocol• The interface from the SG-F to the other entities is a protocol interface when the SG-F and MGC-F or other SG-F are not co-located (e.g. SIGTRAN)

• One SG-F can serve multiple MGC-Fs• Applicable protocols include SIGTRAN, TUA, SUA and M3UA

over SCTPover SCTP

• May perform signaling and media event detection functions such as DTMF detection,

• on/off-hook detection voice activity detection etc• on/off-hook detection, voice activity detection, etc.• Manages its own the media processing resources required to

provide the functionality mentioned aboveM h th bilit t f di it l i b d• May have the ability to perform digit analysis based on a map downloaded from the MGC-F

• Provides a mechanism for the MGC-F to audit the state and capabilities of the endpoints

• Is not required to maintain the call state of calls passing through the MG-F; the MG-F only maintains the connectionthrough the MG-F; the MG-F only maintains the connection state of the calls it supports

• A SIP phone is an MG-F and MGC-F in a single boxA SIP bl t i MG F d MGC F i i l b• A SIP-capable gateway is an MG-F and MGC-F in a single box

• “Hair pinning” of a call by the MG-F directed toward the source network may occur under control of the MGC-Fy

• Applicable protocols include RTP/RTCP, TDM, H.248 and MGCP

10). Service Control Function (SC-F)• SC-F exists when the AS-F controls the service logic of a

f tifunction.• For this reason, the ISC recognizes a separate SC-F.

Examples of SC-F protocols include : INAP, CAP and MAP; p p , ;open APIs include JAIN and Parlay.

11) Media Gateway Function: (MG11) Media Gateway Function: (MG F)F)11). Media Gateway Function: (MG11). Media Gateway Function: (MG--F)F)• MG-F interfaces the IP network with an access endpoint or

network trunk, or a collection of endpoints and/or trunks.p• MG-F serves as the gateway between the packet and external

networks, such as the PSTN, mobile network, etc.• For example the MG-F could provide the gateway between :• For example, the MG-F could provide the gateway between :

• an IP and circuit network (e.g. IP to PSTN),• or between two packet networks (e.g. IP to 3G or ATM).

Its primary role is to transform media from one transmission format to another, most often between :• circuits and packets• circuits and packets,• ATM packets and IP packets, or• analog/ISDN circuits and packets as in a residential gateway.

MGMG--F Characteristics:F Characteristics:• Always has a master/slave relationship with the MGC- F that isAlways has a master/slave relationship with the MGC F that is

achieved through a control protocol such as MGCP or MEGACO

• May perform media processing functions such as media• May perform media processing functions such as media transcoding, media packetization, echo cancellation, jitter buffer management, packet loss compensation, etc.

• May perform media insertion functions such as call progress tone generation, DTMF generation, comfort noise generation, etc.etc.

12.12. Media Server Function (MSMedia Server Function (MS--F)F)The MS-F provides media manipulation and treatment of a

k ti d di t b h lf f li ti It ipacketized media stream on behalf of any applications. Its primary role is to operate as a server that handles requests from the AS-F or MGC-F for performing media processing on packetized media p g p g pstreams.

MSMS F Characteristic:F Characteristic:MSMS--F Characteristic:F Characteristic:• Support for multiple codecs and transcoding• Support for control by multiple AS-Fs or MGC-Fs• Support for multiple concurrent capabilities:

o digit detectiono streaming of tones and announcements (anyo streaming of tones and announcements (any

multimedia file)o algorithmic tone generationo recording of multimedia streamso recording of multimedia streamso speech recognitiono speech generation from text

o speech generation from texto mixing (conference bridge)o mixing (conference bridge)o fax processingo voice activity detection and loudness reportingo scripted combinations of the above

• Performs under the control of an AS-F or MGC-F through a control protocol, with either :p ,

• tight coupling (resource control) or loose coupling (function invocation or scripts)

• Applicable protocols include SIP MGCP and H 248• Applicable protocols include SIP, MGCP and H.248

MGC Building BlocksMGC Building Blocks

Network Example• WirelineWireline

• All-IP Network

• VoIP Tandem Switching

• POTS Carried over IPIP

• Access Network (V5/ISDN) over IP

• Cable Network (e.g. PacketCable™) over IP

• VoDSL and IAD over IP

• Wireless (3GPP R99 Special Case NGN)

• Wireless (3GPP R2000 General Case all IP)

• WCDMA Mobile Network

Acronyms3G Third Generation3GPP 3G Partnership Project (UMTS)AAA Authentication, Authorization and Accounting (IETF)A-F (Call) Accounting Function (ISC)A-F (Call) Accounting Function (ISC)ADSL Asymmetric Digital Subscriber LineAG Access GatewayAGS-F Access Gateway Signaling Function (ISC)AIN Advanced Intelligent NetworkAN Access NetworkAPI Application Programming InterfaceAS Application ServerAS Application ServerAS-F Application Server Function (ISC)ATM Asynchronous Transfer ModeATU-R ADSL Terminal Unit-RemoteA C A th ti ti C t (GSM)AuC Authentication Center (GSM)BG Border GatewayBICC Bearer Independent Call Control (ITU Q.1901)BSSAP Base Station Subsystem Application Part (GSM, 3GPP)y pp ( , )CA Call AgentCA-F Call Agent Function (ISC)

CAMEL Customized Applications for Mobile Network Enhanced Logic (GSM)CAP CAMEL Application Part (GSM, 3GPP)CLI C L I f t tCLI Common Language InfrastructureCM Cable ModemCMTS Cable Modem Termination System (DOCSIS, PacketCable)COPS Common Open Policy Protocol (IEFT RFC 2748)p y ( )CPL Call Processing LanguageDiffServ Differentiated ServicesDOCSIS Data Over Cable System Interface SpecificationDQoS Dynamic Quality of ServiceDQoS Dynamic Quality of ServiceDSL Digital Subscriber LineDSLAM DSL Access MultiplexerDTMF Dual Tone/Multiple FrequencyENUM E.164 Numbering (IETF RFC 2916)FS Feature ServerGGSN Gateway GPRS System Node (GPRS, 3GPP)GK GatekeeperGK GatekeeperGMSC Gateway Mobile Services Switching Center (GSM, 3GPP)GPRS General Packet Radio ServiceGSM Global System for MobilityHFC Hybrid Fiber/CableHLR Home Location Register (GSM, 3GPP)HSS Home Subscriber System (3GPP)

HTTP Hyper Text Transport Protocol (IETF)IAD Integrated Access DeviceIETF I t t E i i T k FIETF Internet Engineering Task ForceIN Intelligent NetworkINAP Intelligent Network Application ProtocolISDN Integrated Services Digital Networkg gISUP Integrated Services Digital Network User Part (SS7)ITU International Telecommunications UnionIUA ISDN User AdaptationIVR Interactive Voice ResponseIVR Interactive Voice ResponseIW-F Inter-working Function (ISC)JAIN Java Application Interface NetworkLDAP Lightweight Directory Access Protocol (IEFT)M3UA MTP3 User Adaptation (IETF SIGTRAN)MAP Mobile Application Part (GSM, 3GPP)MEGACO MEdia GAteway COntrol (IETF RFC 3015 or ITU H.248)MG Media GatewayMG Media GatewayMGC Media Gateway ControllerMGC-F Media Gateway Controller Function (ISC)MGCP Media Gateway Control Protocol (IETF RFC 2705)MG-F Media Gateway Function (ISC)MMAS Mobile Multimedia Application Server (3GPP)MMCS Mobile Multimedia Call Server (3GPP)

MPLS Multi-Protocol Label SwitchingMS Media ServerMSC M bil S i S it hi C t (GSM 3GPP)MSC Mobile Services Switching Center (GSM, 3GPP)MS-F Media Server Function (ISC)MTA Multimedia Terminal Adaptor (PacketCable)NCS Network Call/Control Signaling (PacketCable)g g ( )NGN Next Generation NetworkOEM Original Equipment ManufacturerOSA Open Service Access (3GPP)OSS Operational Support SystemOSS Operational Support SystemPBX Private Branch eXchangePLMN Public Land Mobile Network (3GPP, UMTS)POTS Plain Old Telephone ServicePSE Personal Service Environment (3GPP)PSTN Public Switched Telephone NetworkQoS Quality of ServiceRAN Radio Access NetworkRAN Radio Access NetworkRANAP Radio Access Network Application Part (3GPP)R-F (Call) Routing Function (ISC)RFC Request For Comment (IETF)RG Residential GatewayRSVP Resource ReSerVation Protocol (IETF)

RTCP Real Time Transport Control Protocol (IETF)RTP Real Time Transport Protocol (IETF RFC 1889)SC F S i C t l F ti (ISC)SC-F Service Control Function (ISC)SCP Service Control PointSCTP Stream Control Transmission ProtocolSDP Session Description ProtocolpSG Signaling GatewaySG-F Signaling Gateway Function (ISC)SGSN Serving GPRS System Node (GPRS, 3GPP)SIGTRAN SIGnaling TRANsport (IETF M3UA IUA SUA V5UA Drafts)SIGTRAN SIGnaling TRANsport (IETF M3UA, IUA, SUA, V5UA Drafts)SIP Session Initiation Protocol (IETF)SIP-T SIP For Telephony (IETF Draft)SNMP Simple Network Management ProtocolSPS-F SIP Proxy Server Function (ISC)SS7 Signaling System 7SUA SCCP User Adaptation (IETF SIGTRAN)TCAP Transaction Capability Application Part (SS7)TCAP Transaction Capability Application Part (SS7)TDM Time Division MultiplexingTG Trunk or Trunking GatewayTGCP Trunking Gateway Control ProtocolTLA Three-Letter AcronymTRIP Telephony Routing over IP (IETF RFC 2871)

TUA TCAP User Adaptation (IETF SIGTRAN)UMTS Universal Mobile Telecommunications SystemV5UA V5 U Ad t ti (IETF SIGTRAN)V5UA V5 User Adaptation (IETF SIGTRAN)VAD Voice Activity DetectionVLR Visitor Location Register (GSM, 3GPP)VoDSL Voice over DSLVoIP Voice over IPWAP Wireless Application ProtocolWCDMA Wideband Code Division Multiple AccessXML Extensible Markup LanguageXML Extensible Markup Language

•• Example of Implementation Example of Implementation Softswitch

(MGC)Softswitch

(MGC)

SS7oIPPSTN Networks

Signaling Gateway Signaling Gateway

(MGC)(MGC) Application Server

Application Server

Analog phone

SS7SS7Switch STP Management

SystemManagement

System

MGCP/H.248SIEMENSNIXDORF

ISDN-BRISIEMENSNIXDORF

ISDN Terminals

Access Gateway Access

Gateway

Trunk Gateway

Trunk Gateway

Analog phone

xDSL Terminals

SIEMENSNIXDORF

IP C N k

InternetInternet

IP Customer

ISDN-BRISIEMENSNIXDORF

ISDN TerminalsIP Core Networks

(ISP)Premises

SIEMENSNIXDORFSIEMENSNIXDORF

SIEMENSNIXDORF

IP Clients and Terminals

[2] [2] Sumber : Siemens, Surpass Packet Local Switch

xDSL Terminals

EXTRA SLIDEEXTRA SLIDEEXTRA SLIDEEXTRA SLIDE

TheTheThe The S ft it hS ft it hSoftswitchSoftswitch

Sun MicroSystemSun MicroSystem versionversion

Softswitch ComponentsSoftswitch Components

1.1. Media Gateway Controller (MGC) / Call Agent Media Gateway Controller (MGC) / Call Agent (CA) / Softswitch(CA) / Softswitch•• Hold call processing rules by controls SG & MGHold call processing rules by controls SG & MG•• Hold call processing rules by controls SG & MG Hold call processing rules by controls SG & MG

(to perform the job) : call set up & tear down.(to perform the job) : call set up & tear down.•• Interfaces to the OSSInterfaces to the OSS•• Interworking with other networksInterworking with other networks•• Interworking with other networksInterworking with other networks

2.2. Signaling Gateway (SG)Signaling Gateway (SG)

33 Media Gateway (MG)Media Gateway (MG)

•• Gateway between SS7 network and the nodes Gateway between SS7 network and the nodes managed by the Softswitchmanaged by the Softswitch

3.3. Media Gateway (MG)Media Gateway (MG)•• Handels the media data payload including Handels the media data payload including

codec/compressioncodec/compression•• Supports legacy telephony (PSTN) : CAS/ISDNSupports legacy telephony (PSTN) : CAS/ISDN

33 M di SM di S3.3. Media ServerMedia Server

•• Perform peripheral functions such as DSP IVRPerform peripheral functions such as DSP IVRPerform peripheral functions such as DSP, IVR Perform peripheral functions such as DSP, IVR etcetc

44 Feature Server)Feature Server)•• Provide all the revenue generating features and Provide all the revenue generating features and

services like billing, multiservices like billing, multi--party conferencing etc.party conferencing etc.

4.4. Feature Server)Feature Server)

•• It uses the resources and related services located It uses the resources and related services located on other components of the Softswitchon other components of the Softswitch

•• It may also support certain services to meet It may also support certain services to meet y ppy ppcertain implementation necessity e.g.: certain implementation necessity e.g.: GateKeeper.GateKeeper.

Functional Requirement and Functional Requirement and System CharactiristicSystem CharactiristicSystem Charactiristic System Charactiristic

11 Softswitch (MGC/CA)Softswitch (MGC/CA)• Responsible for bridging with different characteristics,

including the PSTN/SS7, and IP networks :

1.1. Softswitch (MGC/CA)Softswitch (MGC/CA)

g ,– Validation and initiation before establishing phone connections– Managing voice and data traffic throughout the various networks

• It is often referred to as a “Call Agent” (because of its Call g (control messaging functions).

• Also is referred to as a “Media Gateway Controller” (because of its Media Gateway Control functions). These ( y )names are used interchangeably.

• MGC, MG and SG represents the minimum configuration of a Softswitch.

a.a. Functional RequirementsFunctional Requirements• Call control engine• Call control engine• Voice call establishment protocols : H.323, SIP• Media control protocols : MGCP, Megaco/H.248• Class of service and quality of service control• SS7 control protocol: SIGTRAN (SS7 over IP)• SS7 processing (when using SigTran)SS p ocess g ( e us g S g a )• QoS related protocol message handling such as RTCP• Routing, including :

– Routing component : local dial plan (E164 to port mapping)– Routing component : local dial plan (E164 to port mapping)– Digit analysis overlap and/or enblock signaling– Digit translation support for IP, FR, ATM and other networks

• Call Detail Records (CDR) for billingCall Detail Records (CDR) for billing• Bandwidth management control• Provisioning for Media Gateways:

Assignment and real time configuration of DSP resources– Assignment and real time configuration of DSP resources– DS0 channel assignments– Voice transmission (coding, compression, and packetization)

• Provisioning for Signaling Gateways:– SS7 variants– Process Timers– Linkset configuration– Point code or routing configuration

G t k i t ti

b.b. System CharacteristicSystem Characteristic

• Gatekeeper registration

yy• It is CPU intensive. A multi-processor system is most

preferred. A l i d t b i d It’ bl lti l• A large in-memory database required. It’s enable multiple processes to live in memory.

• It deals mostly with IP traffic. A sufficient amount of high-d ti it b i dspeed connectivity may be required.

• A dual-redundancy approach for network connectivity is normally required.

• It requires support for a variety protocols.• Disk storage is primarily used for loggingDisk storage is primarily used for logging.• It must be highly available. There are several methods for

achieving this.

2.2. Signaling Gateway (SG)Signaling Gateway (SG)Creates a bridge between the SS7 network and an IP networkUnder the control of the Gateway Controller a SignalingUnder the control of the Gateway Controller a Signaling Gateway causes a Softswitch to appear like an ordinary SS7 point code (SS7 node) in an SS7 network.The Signaling Gateway only handles SS7 signaling;Media Gateway handles the voice circuits established by established by the SS7the SS7 signaling mechanism.t e SSt e SS s g a g ec a s

SIGTRANSIGTRAN defines a suite of protocols and User Adaptation protocols and User Adaptation layers for ransporting signaling information over IPlayers for ransporting signaling information over IP--based based networksnetworks.If SigTran is used as the protocol between the Gateway protocol between the Gateway ControllerController and the Signaling Gateway, then only MTP1, Co t o eCo t o e a d t e S g a g Gate ay, t e o y ,MTP2, and SigTran reside on the Signaling Gateway. In this case, MTP3 and higher protocol stacks will reside on the Gateway ControllerGateway Controller.

A Signaling Gateway usually supports the following layers :

• SCTP, which is responsible for reliable signaling transport, streaming, congestion avoidance and control

• M3UA, which supports the transport of ISUP, SCCPISUP, SCCP, andM3UA, which supports the transport of ISUP, SCCPISUP, SCCP, and TUPTUP messages over IP

• M2UA, which supports congestion control and the transport of MTP3MTP3 messagestransport of MTP3MTP3 messages

• IUA, which supports the Q.931/Q.921 interface• M2Peer, which supports the MTP3MTP3--toto--MTP2MTP2 interface

• If a proprietary eventproprietary event interface is used between the Gateway Controller and the Signaling Gateway then theGateway Controller and the Signaling Gateway, then the entire SS7 protocol stack resides on the Signaling Gateway (including MTP3, ISUP, SCCP, and TCAP).A signaling gateway establishes the protocol timing and• A signaling gateway establishes the protocol, timing, and message-framing requirement of the SS7 network, as well as the functional equivalents within the IP network.

• Refer to Appendix B for background details on Signaling and SS7.

a.a. Functional RequirementsFunctional RequirementsA Signaling Gateway must support the following functions :g g y pp g• It must provide physical connectivity to the SS7 network

via a TI/El or Tl/V.35 physical connection• It must be able to transport SS7 information between p

Gateway Controller and Signaling Gateway via an IP network

• It must provide a transmission path for voice, video, and optionally data (Data transmission may be supportedoptionally data. (Data transmission may be supported within the Media Gateway)

• Provide Highly Available SS7 operation for telecommunication servicestelecommunication services

b.b. System CharacteristicSystem CharacteristicyyA Signaling Gateway has the following system characteristics:• It is I/O intensive, but not very CPU intensive.• A maximum amount of memory should be available to hold

state information, configuration information, the point code map alternate routes etcmap, alternate routes, etc.

• A disk storage is primarily used for logging; a small capacity may be adequate.

• The Ethernet interface (to the IP network) may require dualThe Ethernet interface (to the IP network) may require dual redundancy.

• It may interface with the SS7 network by using a T1/E1, ith i i 2 D h l d i 16 Dwith a minimum 2 D-channels, and a maximum 16 D-

channels.• Performance and flexibility can be increased using a H.110

or H.100 bus.• High Availability is a requirement, multiple Signalling

Gateways or signalling links are available Redundancy isGateways or signalling links are available. Redundancy is built into SS7 networks by design.

3.3. Media Gateway (MG)Media Gateway (MG)

Provides transport media (voice, data, fax, and video) between the IP packet network and the PSTN.Typically, DSP perform :yp y, p

analog-to-digital conversionvoice/audio code compressionecho cancellationecho cancellationsilence detectionsuppressioncomfort noise generationcomfort noise generationout-of-band DTMF signal transport, etc.

DSPs control the translation of voice into packets for the IP kIP networkAppendix C has more details on Media encoding of digitized audio.

a.a. Functional RequirementsFunctional Requirements

A Media Gateway should support the following :• Transmission of voice data using the RTP transmission

protocol.protocol.• DSP resource and T1 timeslot allocation under control of

the Gateway Controller, as a result of MGCP or MEGACO messages SIP is preferred although optionalmessages. SIP is preferred, although optional.

• Manage DSP resources to provide voice and packet functions for the services mentioned above.

• Support for legacy protocols such as loop-start, ground-start, E&M, CAS, QSIG, and ISDN over T1.

• Support of T1 clear channel configuration for transferringSupport of T1 clear channel configuration for transferring voice traffic payload in SS7 networks.

• Managing T1 resources and links.• Hot plug of DSP and Tl cards• Hot plug of DSP and Tl cards.

• Redundancy and HA strategies for Media Gateway software.

• Ability to scale the Media Gateway including the ports, cards, and nodes without impacting other Softswitchcards, and nodes without impacting other Softswitch components.

bb S stem CharacteristicS stem Characteristic

A Media Gateway has the following system characteristics:/O /O

b.b. System CharacteristicSystem Characteristic

• It is I/O intensive; I/O scalability is required.• The maximum amount of memory may be necessary to

hold state information, configuration information, MGCP , g ,messages, DSP libraries, etc.

• A disk storage is primarily used for logging; a small capacity may be adequatecapacity may be adequate.

• The Ethernet interface (to the IP network) may require redundancy.

• The interface to the TDM network may need to span several T1/E1 interfaces.T1/E1 interfaces.

• Densities of 120 ports (DS0’s) are normal. Typically these interfaces incorporate onboard DSPs to perform several types of compressiontypes of compression.

• H.110 bus can be leveraged for localized system flexibility.• A High Availability configuration may scale the user density.

4.4. Media ServerMedia Server• Usually separately from the Feature Server because Usua y sepa ate y o t e eatu e Se e because

Media Server applications involve specialized media processing (must support high-performance DSP hw).

a.a. Functional RequirementsFunctional RequirementsA Media Server may have the following functionalA Media Server may have the following functional

requirements • Basic voicemail functionality

I t t d f ilb tifi ti il• Integrated fax mailbox, notification may use e-mail or pre-recorded message.

• Voice recognition capability if provided, e.g voice activity g p y p g ydialing can route a voice-activated call by using database lookups, and then route the call.

• Video conferencing capability including video conferenceVideo conferencing capability including video conference setup and transmission via H.323 or SIP.

• Video conferencing capability including video conference setup and transmission via H.323 or SIP.S h t t t bilit t d t t t ’• Speech-to-text capability to send text to a person’s email account or pager device by using voice input.

• Speech-to-Web feature converts key words into text strings, which can be used for Web lookup or Web access.

• Unified messaging is the ability to read voice fax and

bb System CharacteristicSystem Characteristic

Unified messaging is the ability to read voice, fax, and email messages via the same user interface.

b.b. System CharacteristicSystem CharacteristicA Media Server has the following system characteristics:• It is CPU intensive as it may handle a lot of MGCP• It is CPU intensive, as it may handle a lot of MGCP

message traffic.• Several implementation options exists with local or co-

l t d DSP ti CPUlocated DSP resources or native CPU

• The maximum amount of memory may be required for in-d t b l l l hi b ffmemory databases, large local caching buffers,

extensive libraries, and so forth.• A disk storage used for logging can be of small capacity. g gg g y

If DSP libraries, speech patterns are stored, adequate storage is needed on Disk.

• It handles mostly IP traffic if DSP resources are used forIt handles mostly IP traffic, if DSP resources are used for speech processing.

• It typically can be clustered (n+m type) for high il bilitavailability.

5.5. Feature ServerFeature Server

• Feature Server is defined as an application-level server that hosts, a set of business services.

• This may be also referred to as a Business ApplicationThis may be also referred to as a Business Application Server.

• Since most feature servers host business services and communicate over IP networks there are nocommunicate over IP networks, there are no softswitch-specific constraints on how to divide or group application components.

• These value-added services can either be part of the call agent, or they can be deployed separately.call agent, or they can be deployed separately.

• The applications communicate with the Call Agent through protocols such as SIP, H.323 and others.

• These applications are usually hardware independent• These applications are usually hardware-independent but they may require extensive databaseaccess.

Examples of feature services:• 800 number service—This service provides lower call

charges for high levels of incoming calls.Translation of the 800 number to an actual target a s at o o t e 800 u be to a actua ta gettelephone number is provided by the 800 number database. The called party pays for these calls.

• 900 number service This service provides• 900 number service—This service provides information, contest call-in, and public opinion polls.The caller pays for these calls.

• Billing service—Call detail records (CDRs) are created by the call agent. The CDR program has many billing features, such as the ability to apply rates based on , y pp yline type, time-of-day, etc. This service may offer the customer access to their billing record on demand via a voice call or a Webbilling record on demand via a voice call or a Web request.

• H.323 GateKeeper—This service supports routing across domains Each domain (which is handled by aacross domains. Each domain (which is handled by a Softswitch) can register its phone numbers and trunk access numbers with the GateKeeper via H.323. The GateKeeper provides the call routing service (and digit translation) for each H.323 endpoint.The GateKeeper may provide billing and bandwidth p y p gmanagement control to the Softswitch.

• Calling card services—This service allows a caller to access long distance service via a traditionalaccess long distance service via a traditional telephone.Billing, PIN authentication, and routing support are

id d b h iprovided by the service.• Call authorization—This service establishes Virtual

Private Network (VPN) using a PIN authorization.( ) g

• VPN—This service establishes virtual private (voice) networks. These are private networks which can offer the following features:• Dedicated bandwidth (via leased high-speed networks)• Guaranteed Quality of Service (QoS)Guaranteed Quality of Service (QoS)• Enhanced features that do not necessarily adhere to

standardsPri ate dialing plans• Private dialing plans

• Secure encrypted voice transmission• Centrex services—With this service, the service provider

offers features usually found only in large central offices and PBX systems, such as:• Basic features: call waiting, forward, transfer, park, hunt,Basic features: call waiting, forward, transfer, park, hunt,

and voicemail• Convenience features: autodial, speed dial, calling line ID

Customized private dialing plans• Customized private dialing plans• Secure encrypted voice transmission

• Call center services:• Automatic call distribution, which efficiently routes

incoming calls to multiple destinationsincoming calls to multiple destinations• Answering agents based on a configured policy

management schemeSystem CharacteristicSystem CharacteristicA Feature Server has the following system characteristics:

It typically requires moderate to high CPU utilization This is• It typically requires moderate to high CPU utilization. This is dependent upon the specific application.

• A large onboard memory is desirable for low latency.• It may require CPU scalability to scale with traffic and

application enhancements.• Several databases may be located at the Feature server.Several databases may be located at the Feature server.• Adequate disk storage may be budgeted for the application

needs depending on the nature of the application. 100GB to 2TB range for a typical voice mail bank2TB range for a typical voice mail bank.

• The Ethernet interface (to the IP network) may be implemented with dual redundancy.

Long Distance Carrier

Call Progression – Events, Messages, Protocols

STPSTP

SG TG

SwitchSwitchLESwitchSwitchLE STPSTP

SGTG

SwitchSwitchLESwitchSwitchLE

Analog phone

SS7 Networks

Analog phone

PSTNSS7

Networks

PSTN

SoftswitchSoftswitch

Long Distance Carrier IP Networks

Softswitch (MGC)

Softswitch (MGC)

Off-hookDial Tone

DigitsIAM

IAM

Add <

IAM

SIP InviteAdd

Reply

IAMReply

Add

IAMIAM

RingingACMACMACM

SIP 183ACMC

Off-hook

< 700 ms

Sever

seconto answ

Modify

Reply

Ring ToneACMACM

ACMOff hook

ANMANMANM

SIP 200

ANMANM

ModifyReply

ANM

RTP Stream

ral ds w

er< 105 m

s

On-hookREL

RELREL

ByeSubstractReply Substract

ReplyREL

RELREL

RELCRELCRELCRELC SIP ACK

RELCANM

SS7 MegacoSIP-TSIgTran

MegacoSIgTran

SS7[4][4] Sumber : Sun Microsystems, The Softswitch, January 2002

Example of Implementation :Soffswitch Integration using Compact PCI Technology (cPCI)