Multidrop generic framing procedure (GFP-MD)

In metropolitan areas there is a diverse set of requirements for a new network concept: it is desired that a single transport network should serve all legacy networks as well as new datacom networks. The former type of networks requires efficient support for low bit-rate real-time connection oriented services while the latter one would benefit from packet based statistical multiplexing at transport layer. These contradictory requirements make it difficult to develop a single integrated (or converged) network concept serving all the services. The sheer capacity is not a problem today as higher and higher bit-rates and more and more wavelengths can be used. The challenging question is how to share the resources and manage the network in a cost-efficient manner if plain over-provisioning is not acceptable. Furthermore, protecting the existing investments is a real concern for the operators that should not be overlooked. In recent years SDH/SONET based transport networks are considered to be too inflexible, inefficient, and over-complex for the needs of data communications. As the importance of data communications has been increasing, it has been quite natural to search for a replacement for SDH. However, it has turned out that developing such replacement is not a very easy and straightforward task. On the contrary, many useful functions provided by the SDH seem to be complicated to reinvent in other ways. Furthermore, the motivation for replacing SDH is eroding: the recent developments in advanced SDH like Virtual concatenation (VC), Link capacity adjustment scheme (LCAS), and Generic framing procedure (GFP) have made SDH much more suitable for today's requirements. In this paper a novel multidrop network scheme based on GFP is proposed. The multidrop GFP (GFP-MD) is targeted for metropolitan area networks serving various access and virtual private networks. It is primarily designed to be used in limited complexity resilient networks such as dual rings. However, it supports arbitrary network topologies as well. The GFP-MD gives an efficient way to share network resources between slow and medium speed data streams at metropolitan area while providing a seamless interconnection into SDH/SONET based core networks. Furthermore, GFP-MD can be used to support efficient multicast and broadcast for distribution services.