This is the Integrated Services Internet. There has been some doubt about whether it is possible to build routers fast enough to classify packets according to their flow-spec, and to carry out a WFQ insertion. Frame Relay or ATM switch fabric. Routers would operate between site networks, and act as access devices. The second approach is a more integrated approach, attempting to capitalise on the benefits of virtual circuits at one level, and on the flexibility advantages of dynamic IP routing at another.
All nodes provide both functions in some manner.
There are four main proposals for how to achieve this latter architecture. This is a smart technique for matching a flow of IP packets onto a virtual circuit, dynamically, Essentially, flow characteristics are pre-programmed into a recogniser, which only opens VCs for individual flows that are expected to persist long enough. All routes from the routing table are used to generate tags, which are then used in the backbone to indicate a VC to follow.