The independence of 1) the data plane of 802.1Q bridges; 2) the quality of service (priority) features of same; and 3) the compatibility of many of the control protocols utilizable at Layer 2; together mean that it is possible to construct a Layer 2 network upon the concept of a Network Core, a set of VLANs running a single control protocol, but sharing a physical layer and an IS-IS-based protocol foundation, with other Network Cores. The result is a network that can be optimized for several purposes simultaneously. This can provide a structure around which the many competing industrial real-time control protocols can further reduce jitter and latency, even while being used together, to their mutual advantage.
Paper and presentation from the 2012 ODVA Industry Conference & 15th Annual Meeting
Norman Finn, Cisco Systems, Inc.