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Parlay

Posted by kathayat on October 13, 2007

The provision of value-added telephony services is by now mainly in the hands of network operators. This might change soon: OSA and Parlay specify an open, secure interface to the telephony network, which can open the telephony network to 3rd party service providers.

20 years ago, the implementation and deployment of value-added telephony services was the domain of manufacturers of telecom equipment. Telecom services of these days were, for example, call forwarding or televoting. Manufacturers were implementing the services according to the requirements from the network operator. Later, in the early nineties, the concept of Intelligent Networks (IN) was introduced and deployed in the networks. By this, network operators were getting the means to develop and deploy value-added services on their own. The creation of services is done with a Service Creation Environment (SCE). Services are created graphically by putting single service building blocks together to form the service logic chain, and by customising these building blocks. This is still the current method of how most of the value added services are created, both in fixed and mobile networks. Examples of such services are Freephone, Split Charging or Premium Rate services, Televoting, and also the Universal Personal Number.

Parlay: API for new service providers

The Intelligent Networks technology does not allow external service providers to create and deploy services on their own through the network of a network operator. The main reason is the missing security features in IN – a Service Creation Environment has full access to the network operator’s signalling network SS7. Moreover, the third party service provider would have to invest millions into the necessary equipment. To solve these issues, the Parlay group was founded in 1998 by BT, DGM&S (today: Ulticom), Microsoft, Nortel Networks, and Siemens. The goal of Parlay is the specification and realisation of an open, technology-independent Application Programming Interface (API) in telecommunication networks. The Parlay API shall enable network operators, independent software manufacturers and service providers to offer products and services, which use the functionality of existing networks. This should not be restricted to one network type, but comprise various networks (see figure 1).

Standardisation of the API

The efforts of the Parlay group to bring the API specification into standardisation bodies succeeded already one year later. The 3rd Generation Partnership Project (3GPP), in charge of specifying 3G mobile networks, adapted Parlay as the method for creating services in UMTS. 3GPP introduced this API under the abbreviation OSA – Open Service Architecture – which recently was renamed to Open Service Access. The API thus is nowadays referred to as OSA/Parlay API (or vice versa). Meanwhile, the API has also been adapted by ETSI in order to cover the fixed network side. All three bodies jointly develop the standard. Although these bodies partly publish their own specifications, they are all aligned and compatible. In the second quarter of 2002, the most recent version was subject to approval: Parlay 3.1, and OSA 1.1 / 3GPP Rel. 4 in ETSI / 3GPP respectively (1), (2), (3).

Structure of the API

The OSA/Parlay API consists of two groups of interfaces: ‘Framework Interfaces’ and ‘Service Interfaces’ (see figure 2).

The Framework Interfaces provide basic mechanisms prior to the usage of actual network functions. They comprise, for instance, Authentication and Authorisation to identify the application that wants to access the API. After successful authentication, the Discovery function can be used to query information about availability of network functions. Further functions comprise Online Subscription of service features or network functions, and further contractual service usage agreements. The access to the Framework is always the first step for the use of the OSA/Parlay API. Following this, the Service Interfaces can be used, as far as the application is authorised.

The Service Interfaces enable client applications to access the so-called ‘Service Capability Features’ (SCF). They represent the available network functions that can be used to implement telecommunication services for the end-customer. The following list gives an overview of the components contained in Parlay version 3.0, approved in December 2001:

  • Call Control: Setup and control of connections
  • User Interaction: playing announcements, DTMF recognition, Sending of SMS etc.
  • User Status / User Location: e.g. phone switched on/off?, Localisation of the phone
  • Data Session Control: e.g. for volume-based tariffing in GPRS
  • Terminal Capabilities: to query to terminal capabilities
  • Generic Messaging: converting messages, connection to mailbox etc.
  • Connectivity Management: Realising QoS etc.
  • Content based charging: tariffing based on the content of the transmitted data
  • Account Management: Management of prepaid cards in mobile networks
  1. http://www.parlay.org
  2. http://www.3gpp.org
  3. http://portal.etsi.org
  4. http://www.eurescom.de/public/Events/2002/osa-workshop/default.asp 
  5. http://www.eurescom.de/public/projects/P1100-series/p1110

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Open Interface

Posted by kathayat on September 17, 2007

  • Freely available specifications
  • Variety of implementations
  • Wide acceptance among the users

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