The full functionality of DPI is available in case of inline connection into the line before NAT servers and symmetric traffic. The latest requirement means that the inbound and outbound traffic of each subscriber goes through the same DPI platform. The scaling of the platform in the symmetric mode is achieved by channels' aggregation and use of symmetric hash function, as described here: Implementation schemes

One can connect the platform to pass the outbound traffic only by using asymmetric route. The same mode can be used to process mirrored traffic. The platform's functionality is reduced in these cases.