In the modern network space, packetized data traffic of various different protocols (e.g. internet protocol, frame relay, asynchronous transfer mode, etc.) is transported over a common network infrastructure. Each protocol provides its own packet (or frame) size and format standards. Additionally, some protocols (e.g. IP) are specifically designed to allow packets having widely varying lengths. New routing protocols, for example the multi-protocol label switching (MPLS) protocol have been proposed to facilitate multi-protocol traffic across a common network infrastructure.
Under the MPLS protocol, label switched paths (LSPs) are propagated across the network hop-by-hop along a path that is set up at the beginning of a communications session. In a general, the label assigned to the LSP can be different for each hop, with the label conversion being performed by the node serving the respective hop. Resources of each hop (i.e. the node serving the hop) of the path are reserved during set-up of the path, and normally will not be available for carrying other traffic until the path is released.
The mapping of an end-to-end path at the beginning of a communications session characterizes the MPLS protocol as “connection oriented”. Other protocols, (such as IP) which do not transport data over predefined end-to-end paths are referred to as “connectionless”. Typically, connectionless traffic is routed across a network using a shortest-path or least-cost-path routing protocol, such as, for example, the Interior Gateway Protocol (IGP). In general, a metric (e.g. a link distance vector, or a link cost factor) is assigned to each link and used within each router for mapping packet destination addresses to downstream links. The metric is normally provisioned for traffic engineering, and reflects not only geographic distances, but also provisioned bandwidth of each link. A higher metric on a particular link makes that link less attractive for carrying connectionless traffic, so that the IGP will normally operate to route connectionless traffic away from that link. Both connection-oriented and connectionless traffic may be carried over shared network infrastructure. This situation is normally accommodated by adjusting the provisioned IGP metric to reflect an average anticipated amount of bandwidth allocated to the connection-oriented traffic. However, this raises a difficulty in that the amount of resources (e.g. bandwidth) actually available for use by connectionless traffic, on any link, will vary with the resources reserved for connection-oriented traffic. Accordingly, during periods of heavy demand for connection-oriented traffic, the provisioned IGP metric for a link may provide an inflated indication of the amount of band-width actually available for connectionless traffic. This can easily result in undesirable congestion on the link. Conversely, during periods of low demand for connection-oriented traffic, the provisioned IGP metric for a link may provide a deflated indication of the amount of band-width actually available for connectionless traffic. This can result in undesirable under-utilization of the link.
A technique which allows connection-oriented and connectionless traffic to efficiently share network resources is therefore highly desirable.