The MESCAL functional architecture describes from the perspective of a single provider the functions required for the provision of inter-domain QoS services. The architecture decomposes the functions required to provide inter-domain QoS: this enables the development of Inter-domain QoS solutions by breaking the overall problem down into manageable entities while maintaining a holistic view of the problem.

The main functional groups in the architecture are: Service Planning and QoS Capabilities Exchange; Network Planning and Provisioning; Off-line Traffic Engineering; Dynamic Traffic Engineering; SLS Management; and Monitoring and SLA Assurance.

The management plane includes off-line functionality, typically located in management servers outside the network elements. Relevant functions are responsible for (a) interacting with customers and service peers to negotiate contracts and (b) implementing the business decisions of the INP through planning, dimensioning and configuring the network. The control plane covers intra- and inter-domain routing, handling the admission of traffic flows, and dynamic resource management including load distribution and capacity management functions. Typically, control plane functions are embedded within network elements although they are not involved in packet-by-packet decisions. Finally, the data plane is responsible for per-packet treatment, and is configured by the control plane.

The management plane functions run at the epochs of the so-called resource provisioning cycles (RPCs). In MESCAL we define two RPCs – the intra-domain RPC, for off-line intra-domain Traffic Engineering, and the inter-domain RPC for off-line inter-domain Traffic Engineering. At RPCs network resources are optimized to meet predicted demand, including sufficient spare capacity to avoid network reconfiguration at each SLS subscription or renegotiation, while avoiding the inefficiencies of massively over-provisioned resources.

The architecture should be seen as a framework for control and management plane functionality required for deploying and operating inter-domain QoS-based services, although this is not prescriptive in the sense that all functional blocks are mandatory in any particular implementation of an INP. The architecture is independent of the particular algorithms used to implement each functional block, or even of the network technologies used to deploy traffic engineering. This functional model is seen as one of the major exploitable results from MESCAL as it has the potential to influence commercial implementations of QoS-based services as well as standardisation activities.

Further reading:

M.P. Howarth, P. Flegkas, G. Pavlou, N. Wang, P. Trimintzios, D. Griffin, J. Griem, M. Boucadair, P. Morand, H. Asgari and P. Georgatsos, "Provisioning for Inter-domain quality of service: the MESCAL approach," IEEE Communications Magazine, June 2005. [link]

MESCAL deliverable D1.3, "Final specification of protocols and algorithms for inter-domain SLS management and traffic engineering for QoS-based IP service delivery", Chapter 6. [link]