SMS hubbing is a new structure for the international flow of SMS between operators, reshaping the way that international mobile inter-operability works by implementing hubs to intermediate the SMS traffic and to offer a larger SMS coverage. The GSM Association (GSMA) found in SMS Hubbing the solution to a problem that limits the continuing growth of international SMS, culminating to the development of the SMS Hubbing trials in 2006, part of the Open Connectivity project. This initiative created a new structure for international SMS interoperability, as well as developed standards and requirements that SMS hubs should follow. Regardless of the maturity of the operator or number of subscribers, each subscriber expects to be able to send an SMS to other subscribers, regardless of country and mobile network. Background The lack of complete international SMS interoperability is caused by the way the GSM world is interconnected: each operator has a need to establish SMS interworking with all other mobile operators, meaning that international SMS can only transit from one operator to another if there is a bi-lateral roaming agreement in place. While SMS interoperability is limited to bi-lateral interworking / roaming agreements between operators, it is unlikely that full international SMS reach will be achieved by setting up more and more agreements, which are time-consuming and costly to put in place. In addition to that, the revenue benefits of an extra interworking connection might not justify the investment required to set it up in the first place. SMS hubbing enables a broad international SMS coverage for mobile operators (“client operators”) through the connection to independent hubs, who have multiple agreements in place with other operators, therefore being able to route messages on behalf of the client operators. SMS Hubbing works with the same concept of voice connectivity model: rather than relying on costly and multiple individual agreements, voice traffic flows via telehouses, which are basically hubs for voice. In the same way, many operators connect to hubs to transit MMS messages, in an attempt to fix the many interoperability problems with this messaging technology. SMS Hubbing is about simplifying the SMS interworking system, by replacing much of the unproductive, identical investments in international agreements made traditionally by mobile operators. As well as this, SMS Hubbing is about providing a higher level of service to SMS, by introducing end-to-end quality of service through Service Level Agreements (SLAs). It is clear that SMS