Multiservice networks provide more than one distinct communications service type over the same physical infrastructure. Multiservice implies not only the existence of multiple traffic types within the network, but also the ability of a single network to support all of these applications without compromising quality of service (QoS) for any of them.
You find multiservice networks primarily in the domain of established service providers that are in the long-term business of providing wireline or wireless communication-networking solutions year after year. Characteristically, multiservice networks have a large local or long-distance voice constituency and are traditionally Asynchronous Transfer Mode (ATM) Layer 2-switched in the core with overlays of Layer 2 data and video solutions, such as circuit emulation, Frame Relay, Ethernet, Virtual Private Network (VPN), and other billed services. The initial definition for multiservice networks was a converged ATM and Frame Relay network supporting data in addition to circuit-based voice communications. Recently, next-generation multiservice networks have emerged, adding Ethernet, Layer 3 Internet Protocol (IP), VPNs, and Multiprotocol Label Switching (MPLS) services to the mix. IP and, perhaps more specifically, IP/MPLS core networks are taking center stage as multiservice networks are converging on Layer 2, Layer 3, and higher-layer services.
Many provider networks were built piecemeal;a voice network here, a Frame Relay network there, and an ATM network everywhere as a next-generation voice transporter and converged platform for multiple services. The demand explosion of Internet access in the 1990s sent many providers and operators scrambling to overlay IP capabilities, often creating another distinct infrastructure to operate and manage. Neither approach used the current investment to its best advantage.
This type of response to customer requirements perpetuates purpose-built networks. Purpose-built networks are not solely a negative venture. These networks do serve their purpose; however, their architectures often overserve their intended market, lack sufficient modularity and extensibility, and, thus, become too costly to operate in parallel over the long term. Multiple parallel networks can spawn duplicate and triplicate resources to provision, manage, and maintain. Examples are resource expansion through additional parts sparing, inimitable provisioning and management interfaces, and bandages to the billing systems. Often a new network infrastructure produces an entirely new division of the company, replicating several operational and business functions in its wake.
In the early 1980s, the International Telecommunication Union Telecommunication Standardization sector (ITU-T) and other standards organizations, such as the ATM Forum, established a series of recommendations for the networking techniques required to implement an intelligent fiber-based network to solve public switched telephone network (PSTN) limitations of interoperability and internetwork timing and carry new services such as digital voice and data.
The new era of networking is based on increasing opportunity through service pull, rather than through a particular technology push requiring its own purpose-built network infrastructure. Positioning networks to support the service pull of IP while operationally converging multiple streams of voice, video, and IP-integrated data is the new direction of multiservice network architecture. In the face of competitive pressures and service substitution, not only are next-generation multiservice networks a fresh direction, they are an imperative passage through which to optimize investment and expense.
