IPP Request and response comparison

[rajkumar]

If i send a request to CUPS server and CUPS server return a response.
How do i know that which request's response comes,Because some where return that using request id,
But
http://tools.ietf.org/html/draft-ietf-ipp-protocol-04 on this link it is written that
3.6 Request-id

The request-id allows a client to match a response with a request.  This
mechanism is unnecessary in HTTP, but may be useful when application/ipp
entity bodies are used in another context.

The request-id in a response SHALL be the value of the request-id
received in the corresponding request.  A client can set the request-id
in each request to a unique value or a constant value, such as 1,
depending on what the client does with the request-id returned in the
response

and i tried that i update request id with some random number in request header and i didnt update request id in response header with original request id.and job got printed.so i think that request id is not checked by client....

"My question is that how do i know that particular response is for particular request."