Application level switching of transactions at a gateway is provided. The gateway is configured to switch the transaction based on the application level content, a current state of a transport environment, and/or dynamic rules for switching transactions. For example, several possible service providers can be selected for the type of transaction, and the gateway can monitor not only the round-trip time through the network(s) to different possible service providers, but also the time required to complete the transaction at the application level and return a response. The application is chosen on the sending side of the network, and application level formatting is done on the sending side as well. The gateway uses modular code and data, and separate instances of processing code to allow dynamic updating. Rules for application service selection can be selectively uploaded to the gateway from a client. The rules for different available application services can be distributed across different gateways.