1 Reference Models THE OSI & TCP/IP REFERENCE MODELS

1

Reference Models THE OSI & TCP/IP REFERENCE

MODELS

2

Public Switched Telephone Network (PSTN)

• The PSTN includes a number of transmission links and nodes:

Customer Premises Equipment (CPE) – the equipment that is located at the customer site to transmit and receive user information and exchange the control information with the network, it includes PBXs key telephone systems, and single line telephones.

Switching nodes – interconnect transmission facilities at various locations and route traffic through a network.

3

Transmission nodes – provide communication paths that carry user traffic and network control information between the nodes in the network, include the transmission media, transport equipment, amplifiers and/or repeaters, multiplexers and…

Service nodes – handle signaling, which is the transmission of information to control the setup, holding, charging, and releasing of connections, as well as the transmission of information to control network operations and billing (SS7)

Public Switched Telephone Network (PSTN) (Continued..)

4

PSTN Architecture

Central Office PBX

Central Office

Central Office

• Each phone user (subscriber) has a direct connection to a switch in the central office. This is called the local loop

• The local loop has a length of 1 – 10 km

• The switches in the central office are called (local) exchange

• A company which provides local telephone service is called a local exchange carrier (LEC)

Long-haul

Network

Toll switch

(For routing calls to or from other cities)

Individual User station

lines, or Extensions

International Gateway

5

How is voice transmitted?

• Voice can be transmitted in two ways:– Analog voice transmission: each voice

channel is allocated a bandwidth of 3.5 kHz

– Digital voice transmission: analog voice stream is converted in a digital stream:

• Standard scheme for voice call: Obtain 8000 samples per second, each with length 8 bit

6

• Until 1960s:– Entire telephone network is analog– Frequency division multiplexing

• Today:– The local loop is analog.– The rest of the network is digital (based on

TDM)• All digital: When do we get an all digital network?

– ISDN (Integrated Services Digital Network ) is an all digital circuit-switching technology. ISDN is available since the early – 1990s (in Europe) or mid-1990s (US). No wide deployment in US

– Another all digital – but not circuit switched - telephony solution is IP telephony.

How is voice transmitted?

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All Analog telephone network

Sub-scriber

• The telephone switch bundles (multiplexes) multiple voice calls on a high-bandwidth link

• The multiplexing method is FDM

Sub-scriber

Sub-scriber

Sub-scriber

TelephoneSwitch

TelephoneSwitch

8

Analog local loop / digital network

Sub-scriber

• The first telephone digitizes a voice call (8000 8-bit samples per second)

• Switching method is TDM.- Switch bundles multiple calls, by interleaving samples in time. Each receives one 8-bit slot every 125μs

Sub-scriber

Sub-scriber

Sub-scriber

TelephoneSwitch

TelephoneSwitch

1-byte voice samples

9

PBX

Central Office PBX

Central Office

Central Office

• A PBX (Private Branch Exchange) is telephone system within an enterprise that switches calls within the enterprise on local lines, while allowing all users to share a certain number of external lines to the central office.

• The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company’s central office.

Long-haul

Network

Toll switch

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The long-haul network

Central Office PBX

Central Office

Central Office

• Toll or backbone switches provide long-distance connectivity over long distance trunks.

• There are only about 500 toll switches in the united states. Each toll switch can run more than 100,000 simultaneous phone calls

Long-haul

Network

Toll switch

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SignalingSignaling

Signaling: exchange of messages among network entities to enable (provide service) to connection / call Or the communication necessary to set up a call from onesubscriber to another

Before, during, after connection/call

o call setup and tear down

o call maintenance

o measurement, billing

Between:

o end – user <-> network

o network element <-> network element

o end – user <-> end – user

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Telephone network: servicesTelephone network: services point-to-point POTS calls

special telephone numbers:

o 800 (888) number service: free call to customer

o numbers for life

caller ID

calling card / third part charging

call routing (to end user): prespecified, by time-of-day

“follow me” service – allows you to select a temporary alternate phone on campus to receive your forwarded calls.

incoming/outgoing call restrictions

support for cellular roaming: “home” number routed to current cell location

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Intelligence in the networkIntelligence in the network

Telephone companies are looking for providing intelligent services to their subscribers: forward, block, reverse the call charges and record messages.

Network programmability.

Competence by delivering value-added services

This competence led to the standardization of intelligent network architecture.

SS7 – Metanetwork for signaling.

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SS7 Network ElementsSS7 Network Elements

Signaling points (SPs): network equipment that can send or receive signaling messages.

Signaling Links (SLs): links that carry signaling messages ( 56-Kbps or 64-Kbps)

Signaling Transfer points (STPs): intermediate nodes that route signaling messages from one place to another.

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SS7 Network ElementsSS7 Network Elements

SP

SP

STP

STP

STP

STP

SP

SP

Bearer Connection

Network 1 Network 2

SLSL

SL

SL

SL

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SS7 Protocol StackSS7 Protocol Stack

Message Transfer Part (MTP) 1Message Transfer Part (MTP) 1



Signaling Connection Control Part (SCCP) Signaling Connection Control Part (SCCP)

Transaction Capabilities Application Part (TCAP)Transaction Capabilities Application Part (TCAP)

Telephony U

ser Part (T

UP

)T

elephony User P

art (TU

P)

ISD

N U

ser Part (IS

UP

)IS

DN

User P

art (ISU

P)

IN A

pplication P

art (INA

P)

IN A

pplication P

art (INA

P)

Mobile

Application P

art (M

AP

)

Mobile

Application P

art (M

AP

)

Orientation,

Adm

inistration, and

Managem

ent P

art (OA

MP

)

Orientation,

Adm

inistration, and

Managem

ent P

art (OA

MP

)

17

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SS7 Protocol Stack (Cont.)SS7 Protocol Stack (Cont.) Message Transfer Part 1 (MTP1): Contains hardware and firmware resources (Network Cards, Transceivers, and Cables).

Message Transfer Part 2 (MTP2): Responsible for secure transaction of messages between two signaling points.

Message Transfer Part 3 (MTP3): Responsible for routing (Through STP).

Telephony User Part (TUP): Describes the signaling messages for the setup of calls and connections in analog telephony networks.

ISDN User Part (ISUP): Describes the signaling messages for the setup of calls and connections in Digital networks.

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Signaling Connection Control Part (SCCP): Sets up and manages signaling connections, using MTP3 to route messages reliably from one node to another.

Supports both Connection-Oriented and Connectionless signaling contexts. Carries the information that STPs need to perform global title translation. (800 numbers, and number portability)

Transaction Capabilities Application Part (TCAP): allows signaling nodes to do transactions. (e.g. Database access). It contains two types of information: 1. Transaction Portion1. Transaction Portion (starting and ending transactions & maintains the state of the dialog). 2. Component portion2. Component portion (carries the actual protocol queries and responses).

SS7 Protocol Stack (Cont.)SS7 Protocol Stack (Cont.)

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A TCAP message can carry the signaling message of other protocols in the component

portion: Operation, Administration, and Management

Part (OAMP):(OAMP): verification network routing Database and diagnosing link problems.

Mobile Application Part (MAP):(MAP): Responsible for Mobility management, GSM networks.

IN Application Part (INAP).(INAP).

SS7 Protocol Stack (Cont.)

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SP STP STP SPBearer Connection

Network 1 Network 2

SL SL

SCP

SP

SS7 provides a secure data network for signaling messages.

It is easy to add special processing nodes for call processing.

SCP – service control points allows an operator to install and manage services like call forwarding, and call blocking

22

IN Standardization & ImplementationIN Standardization & Implementation

Problems:

1. Framework expanding all the time by nature.

2. Telephony switches offer more and more features with every release and new network.

3. Technology such as GSM and the Internet are constantly changing the environment that IN operates in.

Assumptions:

Upward compatibility

IN – collection of dedicated computers that perform special control functions.

IN – software architecture that runs services.

IN – set of nodes as it is a software framework.

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IN Standardization & Implementation (Cont.)IN Standardization & Implementation (Cont.)

ITU -> INCM – look for the IN from different angles.

2. Global Functional Plane (GFP): Identify the building blocks out of which to construct services. (Looks at services from the providers point of view). Describes the software components that a service providers must deploy to assemble services.

2. Global Functional Plane (GFP): Identify the building blocks out of which to construct services. (Looks at services from the providers point of view). Describes the software components that a service providers must deploy to assemble services.

1. Service Plane (SP): Describes what features a service is composed of. E.g. the freephone service consists of two features: 1. One – number feature: routes incoming calls to a single external number from different telephones.2. Reverse Charging – The owner of the freephone number Pays instead of the caller.

1. Service Plane (SP): Describes what features a service is composed of. E.g. the freephone service consists of two features: 1. One – number feature: routes incoming calls to a single external number from different telephones.2. Reverse Charging – The owner of the freephone number Pays instead of the caller.

3. Distributed Functional Plane (DFP): Reflects the distribution of functions. It is the result of interactions between switches that use protocols to decide how to route the call from source to destination

3. Distributed Functional Plane (DFP): Reflects the distribution of functions. It is the result of interactions between switches that use protocols to decide how to route the call from source to destination

4. Physical Plane (PP): Allocates functions to physical locations or machines. E.g. 1. SSP contains the switch, CCF, and SSF. 2. SCP contains SCF. 3. SMP contains SMF. 4. SDP cont. DB, SDF. 5. IP impl. SRF.

4. Physical Plane (PP): Allocates functions to physical locations or machines. E.g. 1. SSP contains the switch, CCF, and SSF. 2. SCP contains SCF. 3. SMP contains SMF. 4. SDP cont. DB, SDF. 5. IP impl. SRF.

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IN Standardization & Implementation (Cont.)IN Standardization & Implementation (Cont.)

SS7 NetworkSS7 Network

BEPBEP BEPBEP BEPBEP BEPBEP

FEPFEP FEPFEP DBDB

Service Control Point

Ethernet

Memory Channel

FEPs – Terminate the SS7 connections and run the SS7 Protocols

BEPs – Run the actual service software

FEP – BEP selected for three reasons:

1. Performance

2. Scalability

3. Reliability

Alcatel SCP Architecture

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IN and the InternetIN and the Internet

Many operators and manufacturers already started making their IN platforms Internet ready with proprietary solutions.

1. IP, the Internet, and the Web

2. Routers and Gateways: hubs, bridges, routers, gateways, firewalls.

3. Connecting to the Internet using modems via an ISPs.

4. ISDN

5. ADSL, VDSL, and DHN

6. Satellite Networks, LEO

7. Cellular Networks: GSM, GPRS

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IN and The InternetIntelligence on the Internet

The internet is a network of networks.

Not administered by a central operator

Invented for data communication not for voice communication

Communications achieved by the routing packets of data

IP addresses and telephone numbers are differ on format, scope, and the way that they are assigned.

IP Networks have almost the intelligence on the application layer

The Features in IN are centralized and controlled from the SCF. In the Internet they are completely distributed through the network.

Some IN features do not make sense in the Internet: freephone, calling card calls

All of this changes when we use the Internet Infrastructure for telephony.

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IN and The InternetIntelligence on the Internet

Voice, Video, and Multimedia over the Internet

TCP/IP – Designed for communicating data (files, e-mail, web pages) between servers and clients. It breaks the data up into packets and routs them to their destination, where they are reassembled and passed to the receiving application.

Voice and video could be translated into bits using codecs, IP routers should be able to deal with it as they do the routing of a file or a web page.

H323 is the standard for providing Voice and Multimedia services over packet networks. Can involve the following components:

Gateways, Gatekeepers (address translation, call authorization, accounting and billing, call management), Multipoint Control Units.

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The Mobile Dimension

Three types of mobility in telecommunications:

1. Terminal mobility: the terminal is connected to the network via radio interface and can move around freely (e.g. cordless and cellular phones)

2. User mobility: the user can move from one terminal to another and register for incoming and outgoing calls to be made to and from this terminal. (e.g. calling cards)

3. Service mobility: the portfolio of services that a user has subscribed to follows the user as he or she roams to different networks (the concept of exporting content and service to visited location)

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The Mobile DimensionCellular NetworksTypes of Terminal Mobility Networks:

• Cordless: DECT, CT2, …

• Cellular: GSM, DAMPS, …

• Satellite: LEO – EUTELSAT, …

GEO – SKYBRIDGE, …

A cellular network employs many radio cells of limited coverage to cover a large area that gives the following advantages:

1. A mobile phone is always close to a network transceiver, needs less transmission power.

2. channels can be reused in different cells, the capacity of network increases as the cell size shrinks.

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The Mobile DimensionCellular Networks Generations

First Generation (1G): 1980 – analog cellular networks (e.g. AMPS – USA, NMT – Scandinavia, C-450 – Germany, RTMS - France).

Second Generation (2G): 1990 – digital transmission, higher capacity, Better standardization (e.g. GSM, D-AMPS, IS-95, PDC) .

Third Generation (3G): 2000 – Multimedia communications, Mobile Internet, Capacity & services (e.g. GPRS, UMTS)

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The Mobile DimensionGSMGSM radio interface is a mix of Time- and Frequency-division Multiple Access (TDMA and FDMA) with Frequency Division Duplex (FDD).

1001

0101

1101

1111

1100

0110

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4… …

92

93

94

Time Slot

Frequency Channel

Time

0.58ms

200kHz

32

The Mobile DimensionGSM ArchitectureA GSM network consists of three components:

1. Mobile Station (MS): GSM network terminals, they connect to the network through a radio interface and require processing power.

2. Base Station Subsystem (BSS): consists of a base station controller (BSC) and base transceiver stations (BTS).

3. Network Switching Subsystem (NSS): the core network part of the GSM, the key component in NSS is the Mobile Switch Center (MSC); A Visited Location Register database (VLR) – holds the subscriber data for visiting subscribers; A home Location Register database (HLR) – holds the essential subscriber information including information about the VLR to which a subscriber is currently attached.

33

The Mobile DimensionGSM Architecture (Cont.)

BSCBSC

BSCBSC

MSCMSC

HLR

VLRBTS

BTS

BTS

BTS

Base Station Subsystem Network Switching Subsystem

MS

To other MSC or other Networks

34


Procedures that enable mobile terminal when a call arrives.

GSM is divided into location areas, each area covers several radio cells and has a unique identifier transmitted on a special channel in all the cells it contains.

Each mobile monitors this channel. When it detects a change in the broadcast location area identifier (LAI), the mobile terminal knows it has crossed into another location area’s radio cell. at that time it requests a location update from the network.

Mobility Management and Handover

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The Mobile DimensionMobility Management and Handover (Continued)

Two ways that a location update can take place:

1. If the new location area is served by the same MSC and VLR, then the VLR registers the move.

2. If the new location area is served by the another MSC and VLR, then the mobile subscriber information is moved from the old to the new VLR. The HLR is also updated so that it can rout all incoming calls to the new MSC and VLR as follows:

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1. The mobile terminal moves into a new cell, notice that the location identifier for this cell is different, and requests a location update.

2. The VLR requests the subscriber information from the HLR.

3. The HLR sends the subscriber information to the VLR and registers that the subscriber is now attached to the new VLR.

4. The HLR informs the old network of the move and orders the old VLR to remove the record for this subscriber.

37

BSCBSC

BSCBSC

MSCMSC

HLR

VLRMSCMSC

VLR

Location Area A

Location Area B

1

2

4

3

Location Update


38


Handover: When the network and the mobile terminal perceive a decline in quality of the current connection, the network will look for a better channel in a neighboring cell. The mobile terminal must be detached in real time from the radio channel of the old cell and attached to the new channel in the new cell.

39

The Mobile DimensionGSM Security

A subscriber identity module (SIM) stores the GSM subscription.

Each subscription has a unique identifier, the international mobile subscriber identity (IMSI).

The dialed number is called the mobile station ISDN number (MS-ISDN).

The HLR stores the mapping from MS-ISDN to IMSI.

The network authenticates the SIM in the mobile terminal using a secret key algorithm. The visited network will request a location update by sending the mobile station roaming number (MSRN) to the HLR.

40

The Mobile DimensionGSM Security (Continued) The MSRN is an identifier composed of the IMSI and the LAI of the cell where the mobile terminal is located.

The VLR assigns a temporary identifier for the mobile terminal that is locally unique, the temporary mobile station identifier (TMSI). It is much shorter than IMSI and prevents the IMSI from being sent over the air frequently.

The VLR stores the relationship between IMSI and TMSI, and also keep track of the location area of the mobile terminal in the form of the MSRN

when the call is established, the exchange of the digital voice is encrypted using the same secret key as for authentication, but using a different algorithm.

41

MS-ISDN IMSIMSRN

IMSI TMSI MSRN

BSCBSC MSCMSCBTS

HLRVLR

IMSISIM

Visited Network Home Network

Use of Identifiers in GSM

TMSI

MS

The Mobile DimensionGSM Security

42

The Mobile DimensionGSM Connection Services

GSM provides the following services:

1. Basic voice (using 13 kbps codec)

2. Half - rate voice (using 6.5 kbps codecs)

3. Circuit Switched data connection (9.6 kbps)

4. SMS (Store-and-forward Messages of 160 characters)

5. Cell broadcast (93 characters)

6. USSD – transfer of service data between mobile terminal and HLR.

43

The Mobile DimensionGeneral Packet Radio Service(GPRS)

GPRS deployed by operators that already have a GSM network; it is implemented as an extension of the existing GSM infrastructure.

GPRS Radio Interface GPRS occupies free time slots only when a packet is sent or received in a dynamic way.

The maximum number of time slots that a terminal can handle is called mutlislot class of the terminal. It depends on the processing power and radio interface hardware in the terminal.

44

1001

0101

1101

1111

1100

0110

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4… …

92

93

94

Time Slot

Frequency Channel

Time

0.58ms

200kHz

The Mobile DimensionGPRS Radio Interface

Mobile 1 sends on channel 93 in time slot 4

Mobile 2 sends on channel 92 in time slot 2

GPRS packet transmission in free time slots

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The Mobile DimensionGPRS Radio Interface (continued)

Many terminals support more slots for the downlink than for the uplink.

Most terminal multislot classes commercially available are 4+1, 3+1, …, and 2+2.

The data rate depends on the number of slots and the coding scheme employed to map the data packets on the channel bit stream.

The most frequently used scheme offers 13.4 kbps per time slot.

46

BSCBSCBTS

MS

HLR

VLR

MSCMSC

Internet

Internet

PTSN,ISDN,

or GSM

PTSN,ISDN,

or GSM

GMSCGMSC

PCUPCU

GGSNSGSN IP

GPRS-Specific infrastructure

SwitchedCircuit

The Mobile DimensionGPRS Architecture

47

The Mobile DimensionGPRS Architecture

Installing GPRS requires software updates in the BTS, MSC, VLR, and HLR.

The BSC needs to extend with a Packet Control Unit (PCU), which inserts the packet data traffic into the GSM channel structure.

GPRS core network contains:

1. The serving GPRS support node (SGSN), which routs the packets to and from the mobile terminals.

2. The Gateway GPRS support node (GGSN), which acts as the gateway to the external packet network.

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The Mobile Dimension GPRS Mobility Management

The GPRS network is divided into routing areas, to find a compromise between notifying the network of each cell change and the broadcasting of packets for each subscriber to the whole network.

The routing area is the same as, or a subset of , a location area. This gives the following advantages to the GSM-GPRS subscribers:

1. GSM updates automatically imply routing area updates.

2. An incoming GSM call can be paged in the GPRS routing area. Which is smaller than a location area that means less use of radio resources for paging.

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ATTACHMENT AND DETACHMENT PROCEDURE

Before a mobile station can use GPRS services, it must register with an SGSN of the GPRS network. The network checks if the user is authorized, copies the user profile from the HLR to the SGSN, and assigns a packet temporary mobile subscriber identity (P-TMSI) to the user. This procedure is called GPRS attach. For mobile stations using both circuit switched and packet switched services it is possible to perform combined GPRS/IMSI attach procedures. The disconnection from the GPRS network is called GPRS detach. It can be initiated by the mobile station or by the network (SGSN or HLR).

GPRS Mobility Management

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The Mobile Dimension GPRS Connection model

A GPRS subscriber can be in one of the following states:

State model of a GPRS mobile station.

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In IDLE state the MS is not reachable. Performing a GPRS attach, the MS gets into READY state. With a GPRS detach it may disconnect from the network and fall back to IDLE state. All PDP contexts will be deleted. The STANDBY state will be reached when an MS does not send any packets for a longer period of time, and therefore the READY timer (which was started at GPRS attach) expires. An MS in READY state informs its SGSN of every movement to a new cell.

The Mobile Dimension GPRS Connection model (Continued)

52


For the location management of an MS in STANDBY state, a GSM location area (LA) is divided into several routing areas (RA). In general, an RA consists of several cells. The SGSN will only be informed when an MS moves to a new RA; cell changes will not be disclosed. To find out the current cell of an MS in STANDBY state, paging of the MS within a certain RA must be performed.

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For MSs in READY state, no paging is necessary. Whenever an MS moves to a new RA, it sends a “routing area update request” to its assigned SGSN. The message contains the routing area identity (RAI) of its old RA. The base station subsystem (BSS) adds the cell identifier (CI) of the new cell, from which the SGSN can derive the new RAI.


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To exchange data packets with external PDNs after a successful GPRS attach, a mobile station must apply for one or more addresses used in the PDN, e.g., for an IP address in case the PDN is an IP network. This address is called PDP address (Packet Data Protocol address). For each session, a so-called PDP context is created, which describes the characteristics of the session. It contains the PDP type (e.g., IPv4), the PDP address assigned to the mobile station (e.g., 129.187.222.10), the requested QoS, and the address of a GGSN that serves as the access point to the PDN. This context is stored in the MS, the SGSN, and the GGSN. With an active PDP context, the mobile station is “visible” for the external PDN and is able to send and receive data packets. The mapping between the two addresses, PDP and IMSI, enables the GGSN to transfer data packets between PDN and MS. A user may have several simultaneous PDP contexts active at a given time.


55

Distributed IntelligenceParlay & OSA

Intelligent networks were originally designed for telephony networks.

Services are controlled and managed centrally by the network operator.

The IN model doesn’t seem prepared to deliver value-added services in an environment that is becoming heterogeneous and competitive.

Several industry initiatives sought to develop more state-of-the art software architectures for service deployment and operation.

56

Distributed IntelligenceParlay & OSA(cont.)

Parlay & OSA appear to be the technologies that are leading the way in the evolution of IN – the key concept in both is the distribution of service control.

Parlay Concept The network provider is responsible for deploying, operating, and managing services.

The idea of Parlay is to open this interface to third parties, so that others beside the network operator can create and deploy services.

57

SMFSMF

SCFSCF

SSFSSF

PSTN operator

Third-party application

Third-party applicationP

arlayP

arlay

Intelligent network

Public

interface

Proprietary interface

Proprietary interface

Parlay Concept

58

Distributed IntelligenceParlay Concept (cont.)

The Parlay interface also allows access to other network functionalities, such as messaging, charging, QoS negotiation, and mobility management.

Network access to third-party applications is subject to authentication and authorization.

Parlay allow the network provider to set different privilege levels (e.g. some third-party applications can be allowed to receive only notifications from the network while others can control calls and connections)

Parlay also provides facilities for nonrepudiation.

59

Distributed IntelligenceParlay Business Model

Enterprise Administration

Enterprise Administration

ClientApplication

ClientApplication

Parlay ServiceParlay Service

Parlay frameworkParlay

framework

ServiceProvider Service

Provider

Framework provider

Framework provider

Subscription QoS Connectivity Management

Call Control

User Interaction

Messaging

Mobility

Trust and Security

management

Discovery

Integrity management

Service factory

Registration(Not in specified Parlay)

60


Client Application: the third-party application that accesses network features through Parlay interface. (deployed and operated by the enterprise administration)

Framework Interfaces: offer all support functions for Parlay, in particular security and management features (administered by the service provider)

Service Interfaces: offer access to network features, such as call control, messaging, and mobility management (administered by the service provider)

61


Parlay wanted to ensure complete flexibility in mapping Parlay business roles into real-world physical entities.

Parlay allows the provider of the framework interface to be different from the provider of the service interface.

From Parlay to OSA

At the same time that Parlay began gaining momentum, 3GPP and ETSI were working on the OSA interfaces for UMTS.

62

Distributed IntelligenceFrom Parlay to OSA

Because Parlay and OSA are so similar, most manufacturers have been combining both interfaces in one product.

There remains some differences between the two:

a. Parlay specifies only a business model and a set of interfaces.

b. Parlay very explicitly refrains from specifying any requirements on the implementation of the interfaces.

c. Parlay is generic and stand-alone interface specification. While:

d. OSA Specifies more than just an interface and must be seen as a service architecture.

e. ETSI makes recommendations for mapping OSA interface to network protocols like MAP & CAP.

f. OSA is an integral part of the service architecture for UMTS.

63

Distributed IntelligenceOSA interfaces

OSA and Parlay consist of 10 main interface groups:

Interface Short description

Framework Overall security, integrity, and management framework

Call control Setting up, releasing, and managing calls, conferences, and multimedia connections; notifications of call- and connection-related events.

Data session control Setting up, releasing and managing data sessions

User interaction Play or display messages and retrieve user input

Mobility Notifications of user location and user status

Generic messaging E-mails, voice mails, SMS

Terminal capabilities Interrogating a terminal for its capabilities

Connectivity management Negotiation and management of QoS and service Lev agr IP

Account management Creating, deleting, and modifying subscriber accounts

Charging Reservation and charging of units of volume or money

64


Parlay offers two extra interfaces that are not parts of OSA:

a. Policy Management: allows for the creation and management of policy classes and their parameters; to provide application service providers with the possibility of defining service-level agreements (SLAs)

b. PAM. Allows subscribers and terminals in the network to exchange information about presence and availability (buddy lists and instant messaging).

OSA interfaces are defined as a set of object types (classes) – class definitions follow an inheritance hierarchy.

65


Each of the OSA interfaces is specified (in UML and IDL) in four parts:

1. Class diagrams. Provide an overview of the inheritance structure of the interface, its classes and operations.

2. Sequence diagrams. Show key examples of use of the interface in the form of UML message sequence charts.

3. Interface specifications. Provide the formal definition of the interface

4. Data definitions. Provide formal data-type definition in IDL.

66

Distributed IntelligenceGeneral Interface Structure

OSA defines two object classes for each interface on the network side:

1. Ip<Interface> - is the actual interface that offers operations to control resources in the network.

2. Ip<Interface>manager - is a management interface that that contains the operation to start and manage an instance of Ip<Interface>. Its also used to request server-related event notifications like overload conditions.

The client application also has to implement two object classes for each interface:

1. IpApp<Interface> - is a client-side interface that contains operations for receiving results and notifications from the Ip<Interface> interface.

2. IpApp<Interface>manager - is an interface for receiving results and notifications from the Ip<Interface>manager interface.

67

Distributed IntelligenceOSA Interface Structure

Ip<Interface>Manager

Ip<Interface>

OSA server

Creates,

manages

IpApp<Interface>Manager

IpApp<Interface>

Application

Notifications

Notifications,

results

68

Distributed IntelligenceGeneral Interface Structure

These client-side interfaces are often called callback interfaces – they are just like procedure calls in programming languages such as Pascal, operations on objects are synchronous: a client application that requests an operation on an object has to wait for this operation to finish and send back the result.

By putting a callback interface on the client it is possible to decouple the delivery of the result from the request.

Callbacks are used to allow asynchronous communication with synchronous operations.

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Distributed IntelligenceOSA call-control interface

OSA offers several interfaces for call control, some of these interfaces consist of several classes with an inheritance relation.

The figure below shows the inheritance structure (the main classes defined at the server side)

A new object class is defined in a terms of an existing one by inheriting and extending the operations of the parent class

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Distributed IntelligenceOSA call-control interface (Server side)

IpConfCallIpConfCall

IpMultiMediaCallIpMultiMediaCall

IpMultiPartyCallIpMultiPartyCall

IpMultiMediaCallLegIpMultiMediaCallLeg

IpSubConfCallIpSubConfCall

IpMultiMediaCallLegIpMultiMediaCallLeg

IpCallLegIpCallLeg0…n1

0…n

0…n

0…n

0…n 0…n

1

1

1 1

1

71

Distributed IntelligenceOSA call-control interface

There are three main types of call defined in OSA:

1. Multiparty calls: calls with zero or more parties. The connections set up within a call are represented by call-leg objects (connect and disconnect call parties within the scope of a call)

2. Multimedia calls: multiparty calls that allow for multimedia connections between parties. (can create and delete multimedia call legs – each of which can have several streams)

3. Conference calls: multimedia calls in which there exists the possibility of defining additional relationships between the parties (the chair party has privileges to add parties, drop parties, give a party to turn a speak, and interrupting a speaking party). It is possible to create subconferences, and to move parties from one subconference to another

72

Distributed IntelligenceUsing OSA

The complete cycle for using an OSA service consists of three phases:

1. Authentication: before using OSA services, the application and the OSA framework authenticate each other (prevents unauthorized access)

2. Service selection: the application selects the service interface. Request the signing of agreement before using the interface.

3. Service use: only after the authentication and service selection the application start using the actual service.

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Application OSA Framework

Discovery

(1)

(2)

(3)

(4)

Specify an authentication method

(e.g., challenge response)

Compute authentication response

Evaluate authentication response

Create

Services

DiscoverServices

Evaluate authentication

response

Compute authentication

response

Initiateauthentication

authentication method

authenticationFramework

authentication response

authenticationSucceeded

authenticate Client

authentication response

authenticationSucceeded

obtainDiscoveryInterface

Interface reference

Get

Profile

74


Service Selection & Service Agreement

CreateIpCallControlManagerIpAppCallControlManager

Create

(5)

(7)

(8) (8)

(9)

(6)

Application OSA Framework

Prepare service agreement

Evaluate agreement

Evaluate

agreement

Select Service

SignServiceAgreementSignature

SignServiceAgreement

Signature

setCallback

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Call Setup

Create

IpCallControlManagerIpAppCallControlManager

IpAppCall

Create IpCallcreateCall

routeReq

routeRes

routeReq

routeRes

Party A rings

Party A answers

Party B rings

Party B answers

(10)

(11)

(12)

(14)

(13)

(15)

76

Distributed Intelligence OSA Applications

OSA can bring the following added value:

1. Third-party service control. Allow the integration of network features with applications external to the network. (OSA needed to securely access the network’s features)

2. Roaming interface. Current roaming agreements require a high level of trust between the roaming partners. OSA has a security framework, it offers roaming between parties that don’t have an established trust relationship.

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(Continue…)

3. Protocol replacement. OSA can provide a standard programming interface for these network functions; OSA also provides a framework for features that might be added in the future.

4. Content billing. The OSA charging interface can be used to dynamically establish relations between volume and value.

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Example: Taxi Dispatcher

The idea is that when a client calls, his mobile terminal is automatically located and a program automatically alerts the nearest taxi. To implement this service, the taxi dispatcher subscribes to the following three OSA service interfaces offered by the mobile network operator:

1. Call control: to automatically notify the taxi dispatcher of requests for taxis;

2. Mobility: to determine the position of the calling customer and the taxis;

3. Generic messaging: to send a notification to the nearest taxi.

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Example: Taxi Dispatcher (Cont.)

OSA supports two ways of locating taxis (mobile terminals):

a. To ask for the position of all taxis whenever a customer calls.

b. To have the network send periodic positioning information for each taxi, for example every 5 minutes.

The taxi dispatcher develops an application that automatically receives a notification when a customer calls, then locates the customer and finds the nearest taxi, the program send a short message to alert the taxi to pick up the client. This includes the following steps:

1. A customer dials a special number to request a taxi.

80

2. The OSA interface notifies the taxi dispatcher application of the customer’s call. Identifies the calling-party number.

3. The taxi dispatcher requests location of the calling party or the (taxis) through the OSA interface. Forwards it to the MLC.

4. The network locates the calling party or the taxis (this may be

done periodically).

5. Receiving the caller’s coordinates, it looks up the geographic location in a database and determines the nearest taxi.

6. The application sends a short message to the nearest taxi through the OSA interface to pick up the customer at the indicated location.



81

ApplicationApplication



Database

Taxi Dispatcher

OSAOSA

Mobile network

GMLCGMLC

MSCMSC

SMSCSMSC(1)

(4)(3)

(6)

(2)

(6)(5)

TaxiTaxi

Taxi

82

Telecommunications Middleware

Telecommunications Information-Networking Architecture (TINA)

Middleware: is software that runs between machine’s operating system and the applications.

TINA Business Model

TINA architecture

Session model

TINA Service Architecture

1. Computational objects

2. Access session

3. Service session

TINA network-resource Architecture

1. Computational objects

2. Connection establishment

3. Federation

83

Telecommunications MiddlewareTINA Architecture

Service ArchitectureService Architecture

Resource Management ArchitectureResource Management Architecture

Term

inal

Application

Term

inal

Application

ServiceService ServiceService ServiceService

ATM SwitchATM

SwitchISDN SwitchISDN Switch

IP RouterIP Router

Retailer

Connectivity Provider

Consumer

84

Telecommunications MiddlewareService session graph

Service

Session graph

Service

Session graph

Session

member

Session

member

Session relation

Session relation

PartyParty resourceresourceControl

relation

Control

relation

Stream binding

Stream binding

Contains

Is-a Is-a

85

Telecommunications MiddlewareAccess session

The procedure for starting an access session:

1. When the user requests an access session, the PA (provider agent) in the terminal contacts the IA(initial agent) in the network. The address of the IA is always known to any TINA network.

2. The IA consults the subscription database, authenticates the user, and finds the UA(user agent) for this user. (UA can be in a remote network).

3. The UA activates an access session for the user. The PA in the terminal is linked to the UA for the duration of the access session and the user can start using the services.

86

Through the access session, the user can do any of the following:

1. Request a list of available services. The UA will list the services that the user is subscribed to.

2. Request the start of a service session. The access session is always the window through which services are started.

3. Receive invitations from other users to join a service session.

4. Join a service session that is already active.

5. Register remotely at terminals. A user can request to be registered on a remote terminal for incoming invitations to join sessions.

Telecommunications MiddlewareAccess session

87

Telecommunications MiddlewareService session graph

The TINA service session offers the following features that allow parties to modify the session graph:

1. Basic features: such as starting, stopping, and suspending a session;

2. Multiparty features: adding or dropping a party in a session;

3. Stream-binding features: adding or dropping a stream binding to a party in the session;

4. Voting features: voting among parties in the session (permission of a new party to join the session);

5. Control features: for modifying control relations between parties (transferring chairmanship of a videoconference).

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Telecommunications MiddlewareTINA network-resource Architecture

TINA sets up connections in three main steps:

1. Negotiation. The communication session queries all involved terminals and network entities for their capabilities, and selects a set of common capabilities that will allow the connection to be set up.

2. Reservation. The communication session asks all involved terminals and network entities to reserve the selected capabilities.

3. Commitment. If all involved terminals and networks confirm the reservation of the necessary resources, the communication session will then order them to commit the resources and the connection is set up.

89

Telecommunications MiddlewareTINA network-resource Architecture

Terminal

Application

TCSM CSM

LNC IPLNC IP M MTLA IPTLA IP

Service

session

Terminal

resources

Terminal

resources

Network

resources

Network

resources

Negotiate

Reserve and commit

Con

sum

er

Con

nect

ivit

y pr

ovid

erR

etai

ler

CCCC

90


Connection Establishment

The negotiation phase consists of the following steps:

1. The CSM queries the TCSM of each terminal for the terminal capabilities. The terminals respond by giving a list of capabilities they can support (4 slot GPRS)

2. The CSM matches the terminal capabilities listed by each terminal, and defines the common set of capabilities that will allow the requested connection to be established.

3. The CSM tells the TSCM which capabilities are needed and asks the TSCM to select the necessary resources in the terminal.

4. The TCSM asks the TLA to identify the terminal end points that correspond to the requested capabilities. (GSM channels, IP addresses)

5. The selected end-point coordinates are propagated back to the CSM.

91

Telecommunications MiddlewareNegotiation phase in TINA connection setup

TCSMTCSMTLATLA TCSMTCSM TLATLACSMCSM

TLA selects terminal

end points that fit the requested capabilities

TLA selects terminal

end points that fit the requested capabilities

Terminal A Terminal B

CSM selects

common capabilitiesSelect end points Select end

points

Select capabilitiesSelect capabilities

Query capabilities

Query capabilities

Terminal capabilities

Terminal capabilities

End-point addressEnd-point address

End points End points

(1)

(2)

(3) (4)

(5)

92


Connection Establishment

The reservation phase consists of the following steps:

1. The CC contacts the LNC for each subnetwork involved, and asks them to set up the necessary connections within their domain.

2. The LNC asks the terminal to reserve the resources negotiated in the previous steps. The LNC also reserves the necessary network resources.

3. If the selected terminal end-points are available, the LNC asks the TLA to associate them with physical resources in the terminal.

4. The TLA asks the TCSM to link the terminal applications to the physical ports in the terminal that will terminate the connection.

93

Telecommunications MiddlewareReservation phase in TINA connection setup

TCSMTCSMTLATLA TCSMTCSM TLATLA

Terminal A Terminal BNetwork A Network B

LNCLNC CCCC LNCLNC

Network reserve resources

Network reserve resources

Terminal reserve resources

Terminal reserve resources

The TLA associates end points with terminal ports, and the TCSM links the application to them

The TLA associates end points with terminal ports, and the TCSM links the application to them

(3)

OK

OKOKOK

(3)

(4)(4)Associate end points

Associate end points



Terminal end-point settingsTerminal end-point settings

Reserve resources Reserve resourcesSet up

connection

Set up

connection(1)

(2)(2)

94

Service CreationFrom SIBs to Objects The key issue is how to conduct business with the new architectures.

Telecommunications business is determined by the services and offered and their price.

Service creation is all about software engineering.

Telecommunications software is complex, concurrent, must be reliable and deliver high performance.

The INCM recognizes the need for efficient creation of new services. It defines services as compositions of features, which are composed out of elementary building blocks, SIBs.

An IN service-creation environment allows even inexperienced service engineers to create services by clicking together elementary building blocks in a plug-and-play fashion.

95

Service CreationFrom SIBs to Objects

Begin Begin

User InteractionUser Interaction

Service data

management

Service data

management


CompareCompare

ChargeCharge

Continue Continue


Clear call Clear call

(1)

(2)

(3)

(4)

(5)(6)

Play announcement

Get calling card ID from user

Look up calling card in database

Play announcement

Get PIN from user

Validate PIN against card data

Charge communication to calling card

Return to BCP: Continue setting up the call

No match

Return to BCP: Release call

Play error announcement

96

Service CreationFrom SIBs to Objects

The calling card service shows the SIB flow and performs the following steps:

1. A message is played to the user, asking for the calling-card ID, and user input is received in the form of DTMF tones.

2. The calling card data is retrieved from the database using the calling-card ID input by the user in the previous step.

3. A message is played to the user, asking for the PIN code, and user input is received in the form of DTMF tones.

4. The PIN provided by the user is verified against the PIN on the card.

5. If the PIN is correct, the call is charged to the calling card and the call setup continues.

6. If the PIN incorrect (card number or PIN invalid), an error message is played to the user and the call is cleared.

Documents

1 Reference Models THE OSI & TCP/IP REFERENCE MODELS