Optimizing data transmission between a first endpoint and a second endpoint in a computer network

A computer-implemented method for transparently optimizing data transmission between a first endpoint and a second endpoint in a computer network, said endpoints having a directly established data session therebetween, the data session being identified by each endpoint at least to itself in the same way throughout the session, the method comprising:

• relaying data between the endpoints transparently in the session using a network optimization service;
• and
• transparently parameters of at least some of the data transmitted from the second endpoint to the first endpoint using the network optimization service that modifies a capability to receive a response in a compressed format reported by the first endpoint to cause the second endpoint to transmit a response in a compressed format and modifying a compressed response from the second endpoint to the first endpoint by decompressing the response in order to optimize data communications between the endpoints, wherein transparently modifying at least some of the data comprises changing the data, replacing the data, or inserting additional data such that the first endpoint receives different data than was sent by the second endpoint.