How F5 maintain request response mapping?

Can you share which F5 product you are referencing. I'm guessing LTM or ASM? I see you tagged as LTM, so in LTM, F5 doesn't assign a specific transaction ID to HTTP-level responses. BIG-IP internally keeps track of which response came from which request. For example, you can write an iRule that does when HTTP_REQUEST and then when HTTP_RESPONSE and BIG-IP links the two, but i'm not aware of a specific transaction ID.

Can you explain a little more information about what you are trying to accomplish?

For Application Security Manager (ASM), that is different and there is more information associated with requests and responses because BIG-IP tracks them for security reasons and logs them as well.