HSL has the most technically capable and resilient SMS delivery infrastructure in the world, and are committed to the ongoing development and enhancement of their ability to provide a superior service to clients. HSL’s advantage over its competitors comes from their focus on providing a highly reliable service and their focus on the use of SS7 – the telecommunications protocol that provides the most reliable means of SMS delivery.

HSL's SMS Message Delivery Network

In order to reliably deliver SMS messages, Short Message Service Centres (SMSCs) are used to convey messages between mobile users, and between mobile users and applications. HSL utilise a large number of highly reliable SMSC platforms from established mobile operators and their own carrier grade SS7 SMSCs, located in the UK, as part of the delivery infrastructure for inbound and outbound messaging. Key elements of HSL’s infrastructure also include HSL’s own SS7 STPs (Signalling Transfer Points), multiple data centre sites and high availability links between sites, SMSCs and mobile networks.

Part of HSL’s focus on quality and reliability of service includes an ongoing project for directly interconnecting at the SS7 level with mobile networks in the UK and other countries of the European Union. This project involves HSL, as an operator of their own SS7 network, interconnecting with mobile networks for the sending and receiving of SMS. This project is expected to deliver a significant number of direct SS7 interconnects during 2007, further strengthening HSL’s position as a supplier to customers including wireless service providers and mobile network operators.

In July 2005, HSL announced the acquisition of key telecommunications equipment that now forms the core of HSL's own SS7 network dedicated to the delivery of SMS messaging.

HSL's SMSCs (Short Message Service Centres)

The introduction of HSL's own SMSCs, to compliment their existing SMSC connections with established mobile operators, provides exciting service opportunities for HSL and their clients. As with all core messaging software systems operated by HSL, the SMSCs are the result of internal software development by HSL’s software engineering team, with development having commenced in 2000. The currently deployed SMSCs located on HSL’s SS7 network are connected to the global SS7 network, of which the first SMSC went fully live in October 2004.

HSL’s SMSCs comprise integrated HLR (Home Location Register) and MSC (Mobile Switching Centre) capability and have a high degree of functionality for inbound and outbound (MO/MT) SMS. SMSC platforms communicate directly with the SS7 network to provide low latency, highly reliable means of SMS delivery.

HSL have introduced further SMSC platforms into service during 2005 and 2006, on a shared and dedicated basis, and plan to increase service offerings to clients based on these platforms.

Data Centres / POPs

The services operated by HSL are provided using HSL's own server infrastructure located at five geographically separate and independent sites located in Europe and the USA. These points of presence (POPs) allow customer access to HSL’s network infrastructure. The infrastructure is designed to allow for a failure of a site and for service availability to be unaffected.

Physical Security: Sites operate a strict security policy where site monitoring and access controls are in place. Access to service infrastructure and controls is restricted to qualified and authorized engineers.

Power Supplies: The Edinburgh Gyle (UK) site has dual independent 11kV feeds, backed up by dual battery string Chloride UPS systems and Cummins 1.4 Megawatt and 0.8 Megawatt diesel generator sets which are tested on a monthly basis. The Livingston (UK) site utilizes an array of APC UPS systems and has recently been upgraded to increase supply duration in the event of power failure. The Dulles, Virginia (USA) site employs UPS systems and back-up generators to ensure service availability through the longest power outages.

Environmental Control: Fully redundant air handling units provide a constant fresh airflow. The air handling units vary the air temperature in order to match power dissipation.

Traffic Handling: In normal operation all sites dynamically share SMSC connections and load balance customer traffic over all suitable service SMSCs. In the event of an interruption to connectivity between sites, each site automatically operates independently and handles traffic without any impact to customer service.

Connectivity: Each site utilizes different ISPs for providing access to the Internet. Our Livingston (UK) site is served by a resilient connection via multiple links to different core routers at the serving ISP. Our Edinburgh Gyle (UK) and Dulles, Virginia (USA) sites employ BGP and multiple ISPs to provide a highly resilient Internet connection.