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High Availability, Scalable SIP Media Gateways for International Customer Care Contact Center Operations


WNS (Holdings) Limited (NYSE: WNS), is a leading global business process solutions company. WNS offers business value to 200+ global clients by combining operational excellence with deep domain expertise in key industry verticals, including Travel, Insurance, Banking and Financial Services, Manufacturing, Retail and Consumer Packaged Goods, Shipping and Logistics, Healthcare and Utilities. WNS delivers an entire spectrum of business process outsourcing services such as finance and accounting, customer care, technology solutions, research and analytics and industryspecific back-office and front-office processes. WNS has delivery centers worldwide, including China, Costa Rica, India, the Philippines, Poland, Romania, South Africa, Sri
Lanka, UK and US.

WNS was assisted in the planning and deployment of this project by AGC Networks. AGC Networks Ltd. (www.agcnetworks.com) is India’s leading solutions integrator in the field of unified communications, AV solutions, collaboration, network infrastructure, information security and consulting & PSO.


WNS’s international customer care contact center operations had been running very successfully for years. International traffic was collected at two PSTN interconnection points in the US, and the UK by using an Avaya contact center solution based at several sites in India, Europe, Asia and South America. At each of these locations, a Nortel Passport multi-service switch was installed which was connected on one side to the local PSTN provider via T1 connections and on the other to international leased lines, terminating at another Passport switch in India. In India, the Passport switch was connected via DS1s to the Avaya contact center infrastructure.

WNS was faced with the challenge of managing its legacy Nortel Passport devices that were at full capacity and reaching end-of-life. WNS needed a cost-effective solution with a future-proof roadmap designed to support IP/MPLS and VoIP technology. The replacement solution had to offer scalability and reliability and ensure high voice quality. Furthermore, the solution would have to enable future integration with CTI, SIP IVR and other adjunct applications to deliver best-in-class customer service.


WNS’s plans included the replacement of its underlying data transport infrastructure from expensive leased lines to a packet switched network based on Multiprotocol Label Switching (IP / MPLS). The inherent resilient nature of MPLS ensured a straightforward introduction of high levels of redundancy in the network and installing the back-up of a series of Avaya Session Manager servers in several locations apart from India. If for any reason the Session Manager in India became unavailable, the system could still continue to operate without interruptions.

With the network infrastructure moving to IP, WNS chose to replace its voice systems with VoIP devices. In the two target sites in the US, WNS deployed AudioCodes Mediant 3000 high-density and high-availability media gateways. Each Mediant 3000 can support up to 3 DS3s with 2,016 channels per chassis, reducing overall equipment costs. They are housed in a compact 2U chassis, resulting in savings in rack space, power consumption and cooling requirements. The Mediant 3000 supports high availability of carrier-grade, including redundant power supplies, network interfaces and voice processing boards, ensuring the highest degree of reliability.

AudioCodes Media Gateways are fully inter-operable with many 3rd-party systems, both TDM and VoIP. As a result, integration with both the Avaya Session Manager and the respective PSTN operators in the US was achieved smoothly.

The high performance IP / MPLS WAN infrastructure meant that the SIP signaling could be passed between the Session Manager in India and the Mediant 3000 gateways reliably. In parallel, the voice packet streams were also securely transported by the MPLS network between the US and the various customer care contact center locations. All of this ensured that despite the large geographic distances, very high call quality could be maintained, thereby enhancing the user experience of WNS’s customers calling the WNS contact centers.

“With AudioCodes Mediant gateways in place, we are assured that our migration to an all-IP backbone will go smoothly. With this new investment, we believe that the scalability we need in our business will become easy.”

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The benefits delivered to WNS include:

Scalability – With each Mediant 3000 supporting up to 3 DS3 interfaces, the company can expand its capacity without the need to add additional equipment

Low Bandwidth Utilization – Mediant 3000’s advanced call processing capabilities maintain low bandwidth consumption while ensuring high voice quality

Small Footprint – The compact Mediant 3000 hardware platform frees up costly rack space and reduces power and cooling costs

Reduced Capital Expenditure – A single high-capacity Mediant 3000 can replace several smaller devices

Carrier-grade Reliability – Built-in redundancy at various levels ensures business continuity and customer satisfaction

Additional Application Integration – Multiple SIP-based application platforms to improve the quality of customer service and customer contacts