9-IJAEST-Volume-No-2-Issue-No-1-A-comprehensive-study-of-next-generation-network-platforms-(Asterisk by ISERP ISERP

VIBHA KASTURI et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 2, Issue No. 1, 061 - 066

A comprehensive study of next generation network platforms (Asterisk and FreeSWITCH) VIBHA KASTURI Student ME (IT), University institute of engineering and technology Panjab University, Chandigarh Chandigarh, INDIA vibhakasturi@gmail.com*

Keywords-next generation Asterisk; FreeSWITCH

network;

softswitch;

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I. INTRODUCTION The communication era start with TDM based packet switched network (PSTN) and at present all communication over network is through next generation network. In PSTN all voice traffic is transported over TDM and controlled by a hierarchy of local (LEX or Class 5) and transit (TEX/Class 4) circuit switches. The voice-related signaling network (ISUP and INAP) is handled by the SS7 signaling network. PSTN a circuit switched well established, easy to maintain technology cannot provide mobility and are less scalable. Optimum usage of bandwidth is not achieved in PSTN networks. Thus to non-speech communication as IP packets more scalable, efficient packet- switched next generation networks integrate with PSTN to provide concurrent transmission of heterogeneous data and various value added services at very low cost.

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A next generation network (NGN) is a broad term to describe key architecture evolutions in telecommunication core and access networks. The general idea behind NGN is that one network transports all information and services (voice, data and all source of media such as video) by encapsulating these into packets. According to International Telecommunication unit (ITU), A NGN is a packet based network which can provide services including Telecommunication services and able to make use of multiple broadband, Quality-OfService enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies. It offers unrestricted access by users to different service providers. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users [1]. Next generation network can be defined by six criteria as

Abstract— Next generation network is a network that delivers all telecommunication services (data, voice and video) using single packet based infrastructure. The paper gives an introduction to next generation networks, need of next generation networks and various next generation network platforms implemented in telecommunication industries such as Asterisk, FreeSWITCH

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Packet oriented network

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Support broad variety of services (Voice over IP, Data, multimedia)

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Openness and flexibility regarding new services

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Separation into different layers using open interface

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Application focused-access independent

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Integration of existing infrastructure

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VIBHA KASTURI et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 2, Issue No. 1, 061 - 066

NEED FOR NEXT GENERATION NETWORK

A. Increasing demand of bandwidth Applications such as IP voice and IP video conferencing which are becoming the norm, along with the trend to consolidate and virtualized servers from the branch to the data centre, are driving high bandwidth requirements. B. Cost Effectiveness Many businesses, running two or more legacy networks can be very costly (each requires individual maintenance contracts, separate pieces of kit etc) and legacy IP networks prohibit the growth organizations are looking at in current times. C. Need for value added services Due to saturation of both fixed and mobile telephony services the need of new value added services has increased successively

NGN Area

Open, Standardized Interface Control layer Open, Standardized Interface

Core Network

Transport layer (Packet mode) Related To NGN

Multiple Access Networks Terminals

D. Growing energy for IT business To prepare new revenue stream for IT business and to develop a new high tech market.

Service layer (Operator and third parties)

II.

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III. NGN ARCHITECTURE NGN's architecture is based on decoupling transport and service layers. Basically, that means that whenever a provider wants to enable a new service, they can do it straight upon defining it at the service layer without considering the transport layer, i.e. services are transparent to transport, Figure 2[2]. Transmission, linking, routing and services in legacy networks are integrated vertically. Here different networks were designed for different services (telephony, video, and data). In contrast to legacy networks, next generation networks are characterized by an open architecture and the horizontal connection of different layers. The common NGN infrastructure is implemented with the transport layer, which is based on packet technology and used by different services. Information transfer between the source and the destination is transferred in an identical way, irrespective of whether it is a telephone call, an internet session, a video connection or a movie. The application service layer is logically and physically separated from the transport layer, which enables

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Fig 2 Next Generation Network Architecture Principle

the independent development of particular network segments. Different servers, which are separated from the transport, control different services - these include voice telephony, ecommerce, video-ondemand, etc. Adding a new service requires only a new server, which, via the transport layer, is accessible to all users connected to the network over interfaces that have different bandwidth and are implemented with different technologies. The various components on which next generation network are internet protocols, session initiation protocol (SIP) and multi protocols. SIP is an application layer UDP based peer to peer protocol, which establishes a connection between end users. SIP is a signaling/Control protocol. The transfer of data such as voice, text, audio, video etc occurs through other transport protocols such as RTP (real time transport protocol). Other components are Softswitch, gatekeepers. Softswitch transport or control the voice calls related to IP also called as VoIP (Voice over IP). Gatekeepers convert the analog or digital signals

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VIBHA KASTURI et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 2, Issue No. 1, 061 - 066

IV.

BENEFITS OF NGN

A. Fast and affordable NGNs are built to handle a variety of technologies; they are built Ethernet ready and able to handle large bandwidth [3]. Having this speed available reduces the risk involved in changing or upgrading applications. B. Simplicity NGNs simplify network structure, introducing fewer but more powerful nodes compared with traditional circuit-switched nodes. By separating the control layer from the transport layer, new pointsof-presence can be implemented safely, rapidly and cost effectively.

NGN is designed in such a way to give customers soft changes, when needs grow. NGN can carry the highest class of voice traffic. Scalability enables organizations to ramp up very quickly and utilize the services as needed as opposed to the traditional model of investing in additional hardware or resources to anticipate increased capacity. D. Converged and multiple-service

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Integrated architecture of NGN provides lower costs for the delivery of multiple services. Not only can the Cable & Wireless MSP run different converged services it's also more robust, recovering from network faults in a fraction of a second. E. Local and global

All MSP services can be used internationally, ready to serve branches or offices overseas. Clients can run high availability multiple service data networking across the same architecture, reducing the cost to run networks. F. NGN & Cloud Computing NGN is also critical to making cloud computing (and related services) a reality. Cloud computing is effectively an alternative to an on-premise solution

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Managed services and infrastructure provisioning are readily available in next-generation networks to support enterprises' growing appetites for information and services. V.

VARIOUS NEXT GENERATION NETWORK PLATFORMS

Softswitch is the core element of next generation network in control layer. IP SoftSwitch is a platform that allows implementing various types of Voice over Internet Protocol (VoIP) services, with retaining shared, uniform management interface. The International SoftSwitch Consortium defines the term SoftSwitch as a â&#x20AC;&#x153;Media Gateway Controllerâ&#x20AC;? (MGC) which control network elements that mediate between, route or translate different data streams. From the soft-switching technology can be seen, the next generation network according to the two main routes to development: The first line is mainly embodied in circuitswitched network equipment has been divided into physically separate control plane and bearer plane softswitch media gateway part of the end-user business characteristics and the basic feel changes in the way access. The second route is to achieve a true end to end IP service features, and introduces a new voice, realtime multimedia applications, including users and other groups to SIP/H.323 terminal access to the network, network architecture and business delivery method (such as SIP mode) is completely different from the traditional networks. The 3GPP-R4, R5 and so the evolution of architecture is also exactly consistent with the evolution of next generation network, for the final fixed and mobile broadband networks to provide integrated. Another important next generation technology is software based PBX (private branch exchange).

C. Scalable

that involves securing computing power, and tapping into a cloud for hardware usage of software without the standard license-based models. Cloud computing deliver value-added managed telecom services via global private networks or cloud. Customers increasingly prefer the ease and convenience of not having to bother about infrastructure investments and making utility based payments for their IT services and applications.

into data packets for transmission. Softswitch also manage e-working of gateways.

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Drivers for various VoIP protocols. Drivers for PSTN interface cards and devices. Routing and call handling for incoming calls. Outbound call generation and routing. Media management functions (record, play, generate tone, etc.). Call detail recording for accounting and billing. Transcoding (conversion from one media format to another). Protocol conversion (conversion from one protocol to another). Database integration for accessing information on relational databases. Web services integration for accessing data using standard internet protocols. LDAP integration for accessing corporate directory systems. Single and multi-party call bridging. Call recording and monitoring functions. Integrated "Dialplan" scripting language for call processing. External call management in any programming or scripting language through Asterisk Gateway Interface (AGI)

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Event notification and CTI integration via the Asterisk Manager Interface (AMI). Speech synthesis (aka "text-to-speech") in various languages and dialects using third party engines. Speech recognition in various languages using third party recognition engines. KEY APPLICATIONS:

A. Asterisk as PBX Asterisk can be configured as the core of an IP or hybrid PBX, switching calls, managing routes, enabling features, and connecting callers with the outside world over IP, analog (POTS), and digital (T1/E1) connections. Asterisk runs on a wide variety of operating systems including Linux, Mac OS X, OpenBSD, FreeBSD and Sun Solaris and provides all of the features of a PBX including many advanced features that are often associated with high end (and high cost) proprietary PBXs. Asterisk's architecture is designed for maximum flexibility and supports Voice over IP in many protocols, and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.

VI. ASTERISK Asterisk is software that turns an ordinary computer into a communications server [5]. Asterisk powers IP PBX systems, VoIP gateways, conference servers and more. It is used by small businesses, large businesses, call centers, carriers and governments worldwide. Asterisk is free and open source written in C for LINUX platform, sponsored by Digium[6]. Asterisk is often referred as „Open Source PBX‟ that provides voicemail services with directory, call conferencing, interactive voice response and call queuing. It supports voice over IP protocols such as SIP, Media Gateway Control Protocol (MGCP), Inter Asterisk eXchange (IAX) and H.323, Skinny Client Control Protocol (SCCP). The building blocks of Asterisk are:

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The various IP based next generation network techniques presented in this paper are Asterisk, and FreeSWITCH.

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B. Asterisk as a Gateway It can also be built out as the heart of a media gateway, bridging the legacy PSTN to the expanding world of IP telephony. Asterisk‟s modular architecture allows it to convert between a wide range of communications protocols and media codecs. Asterisk as a feature/media server. Asterisk can provide IVR services, can act as a conference bridge, can replace legacy voicemail system, perform Unified messaging and can act as a telephony interface for websites. C. Asterisk in Call centers and Public Networks Asterisk has been adopted by call centers around the world based on its flexibility. Call center and contact center developers have built complete ACD systems based on Asterisk. Asterisk has also added new life to existing call center solutions by adding remote IP agent capabilities, advanced skills-based routing, predictive and bulk dialing, and more.

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VIBHA KASTURI et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES Vol No. 2, Issue No. 1, 061 - 066

Internet Telephony Service Providers (ITSPs), competitive local exchange carriers (CLECS) and even first-tier incumbents have discovered the power of open source communications with Asterisk. Feature servers, hosted services clusters, voicemail systems, pre-paid calling solutions, all based on Asterisk have helped reduce costs and enabled flexibility.

Various characteristics of FreeSWITCH are:

Asterisk support various call control features such as call waiting, call divert, remote call pickup, talk detection, three-way calling, Supervised Transfer, Trunking etc. it also support a number of codecs such as ADPCM(Adaptive Differential Pulse Code Modulation), G.711. G.722

B. Threaded Model FreeSWITCH has a threaded model to support parallel operations. Every connection has its own thread and events are pushed in to thread by event handlers.

C. Dynamic Modular Architecture FreeSWITCH has a modular architecture. It installs with a basic set of modules for the usual iPBX (private branch exchange) tasks, and then additional features come from whatever modules user can find or code by own. Different modules can be used dynamically as:

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VII. FREESWITCH FreeSWITCH is released as open source under MPL (Mozilla Public License) in 2006. It is a crossplatform telephony system designed to transfer multimedia data such as speech, video or text over the IP network [7]. FreeSWITCH support various communication technologies such as Skype, SIP, H.323, Google talk etc. FreeSWITCH has built on following platforms  Linux(x86& x86-64)  Windows (MSVC 2008 & VC++ EE 2008)  Mac OS (Intel & OS)  Free BSD6

A. Distributed Architecture FreeSWITCH is implemented in a distributed manner as opposed to traditional centralized manner of PSTN. In a distributed network processing takes place at various points throughout the network. Thus if a single point fails, the network operations remains unaffected. It also increase scalability

FreeSWITCH is a back-to-back user agent (B2BUA) [3]. B2BUA is a logical element in SIP protocol. A back-to-back user agent operates between both end points of a phone call or communications session and divides the communication channel into two call legs and mediates all SIP signaling between both ends of the call, from call establishment to termination. A B2BUA may provide the following functions: 

Call management (billing, automatic call disconnection, call transfer, etc.)

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FSAPI interface allows the addition of commands that can be accessed remotely. APPLICATION interface allows creation of custom IVRs and call routing apps. XML interface allows real-time dynamic access for user directory and configuration. Endpoint interface connects IM and phones. Allows third party modules and extensions to customize application without having to start from scratch

D. Miscelaneous features FreeSWITCH can act as media gateway, media server, and PBX or session border controller. A number of features, codecs and protocols supported by FreeSWITCH are:

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network interworking (perhaps with protocol adaptation)

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Hiding of network internals (private addresses, network topology, etc.)

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SIP, H.323, IAX2 Google Talk and Jabber support Centralized user and domain directory Stereo call recording

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Software-based conferencing Configuration files and call records in XML Interactive voice recording and call attendant Narrow and wideband codecs Multiple SIP registrations per user account NAT support Message-waiting indicator CONCLUSION

[1] Next Generation Network working definition, ITU-T 2004,website:http://www.itu.int/ITUT/studygroups/com13/ng n2004/working_definition.html, July 2009. [2]

Zohreh Ayatollahi - Saeede Sarukhani - Fatemeh Fayazi Zahra Askary Roknabady - Afsane Madani, “Interoperability problems in next generation networks” First ITU-T Kaleidoscope academic conference, 62-61-124410/CFP08383, 2008 [3] Sunanda Das, MD cable and wireless, India, “The next generation network evolution”, November 18, 2009, http://voicendata.ciol.com/content/ContributoryArticles/109111801.asp

[4] “Network technology evolution strategy and circuit domain”, http://www.tekbar.net/cost-and-investment/networktechnology-evolution-strategy-and-the.html [5] http://www.asterisk.org/

[6] http://www.digium.com/en/

The present paper gives as overview of present telecommunication technology i.e. next generation networks. A brief idea of next generation network architecture has been presented. The paper introduces the software based private branch exchange technology i.e. Asterisk and a SIP based back to back user agent FreeSWITCH.

REFERENCES

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[7] http://www.freeswitch.org

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[8] Anthony Minessale, Darren Schreiber, Miheal S. Collins. FreeSWITCH 1.0.6: Packt Publishing July 2010. ISBN 1847199968

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