Exactly as described, this sets the outer, or Service, VLAN ID stamped onto generated packets, applicable only when EncapType is set to QinQ. Because this only takes effect under QinQ encapsulation, changing this value while the profile's EncapType is actually set to dot1q or untagged has no visible effect on the next test run, a common point of confusion when an operator is trying to change VLAN tagging on a profile that isn't in QinQ mode. For example, setting this to 100 on a QinQ-encapsulated profile stamps every generated test frame with outer VLAN 100, matching whatever S-VLAN the customer's actual service is provisioned on.