The ProxySG sends to the ICAP server to retrieve the ICAP server's default configuration settings

You can trigger the OPTIONS message either by clicking Sense-Settings button on the Edit  ICAP Service Dialog in  Configuration > External Services > ICAP  of the ProxySG's Managment Console.

Or by  executing the sense-settings command from the ProxySG's command line interface (CLI).

sample: sense-settings request for ICAP service name "icap_response" by CLI

ProxySG#
ProxySG#configure terminal
Enter configuration commands, one per line.  End with CTRL-Z.
ProxySG#(config)external-services
ProxySG#(config external-services)edit icap_response
ProxySG#(config icap ICAP_response)sense-settings
  ok
ProxySG#(config icap ICAP_response)