In 2011 GeoServer made significant steps forward to support INSPIRE View Services based on WMS 1.3.0. For those of you not familiar, INSPIRE is the European Spatial Data Infrastructure. At the end of this effort there was still a missing piece — supporting harmonized layer names.
What's a harmonized layer name? Simply put it means that the WMS needs to advertise its layer according to a pre-defined name which is listed in the INSPIRE data specifications. If you were to look at table 19 of the data specification for transport networks you'd see that there is a layer which should be named "TN.CommonTransportElements.TransportNode". Historically you were never able to achieve a harmonized layer name because GeoServer outputs the namespace prefix in front of the user defined name.
To remedy this OpenGeo utilized work done on GeoServer virtual services. The namespace prefix on a virtual service does not make layer names unique and was dropped. For technical details see JIRA issue 5016 and please note that this work is only available in the GeoServer 2.2 release.