Responses to SGPs

Hello Folks

Section
1.5.2.  Address Mapping at the ASP

says

   An ASP routes responses to the SGP that it received messages from.
   The response will utilize the routing context from the received
   messages.


What messages are meant by "response" in this context?

I assume these are response messages triggered by SUA layer itself
(like CLDR, ERROR, etc.). Response messages sent by SCCP/SUA users can
be sent to any SGP, unless they use CO Service.

Apropos, how can it be guaranted that CO messages go to the same SGP?
Shall there be a DRN label per SGP?

Thank you in advance
--
Ilie