This string, up to 32 bytes as an absolute value or regular expression, sets the site-of-origin value this policy term's action applies to a matching VPN route; leaving it unset makes it zero length. An admin uses it together with csRtPolicyTermActionVpnSooOp set to 'set' to stamp routes with a particular originating-site marker. For example, setting csRtPolicyTermActionVpnSoo to a value identifying 'site-east' tags matching routes so other sites can recognize and filter on their true origin.