Hybrid transport solutions for TDM/data networking services

Abstract

There is a growing demand for native data transport services for enterprises and corporations across public transport networks. Recently, equipment vendors have begun to incorporate a variety of LAN and storage area network interfaces, notably Ethernet, Fibre Channel/FICON, and ESCON, on traditional metro and long-haul transport equipment. Embracing Ethernet and SAN technology enables the introduction of flexible high-capacity transport services optimized for data networking. Transport operators may thus offer both enterprise-centric connectivity services, such as transparent LAN connectivity and virtual LAN services, as well as traditional bandwidth services, such as private lines, while preserving the operations and management infrastructure of the existing public networks. In this article we discuss the benefits of a hybrid Ethernet/TDM transport solution.

On Bandwidth Tiered Service

“…The emergence of framer technologies such as virtual concatenation (VCAT) [9] coupled with the link capacity-adjustment scheme (LCAS) [25] enable providers to make significantly more efficient use of the existing SONET/SDH infrastructure [10], [13], [20], [25]. Virtual concatenation allows finer granularity for provisioning of bandwidth services, making it possible to configure service tiers in any multiple of 64 Kbps.…”

“…Given a set of demand points, , and a constant , find a real and a feasible set of supply points, , so as to minimize the objective function (20) under the constraints: integer, . The term in (20) represents the excess bandwidth penalty, as before.…”

“…The term in (20) represents the excess bandwidth penalty, as before. However, the objective function for TDM-DPM1 includes the additional term , where is some constant related to the operation of the system, as we explain shortly.…”

“…This relative overhead, which increases as the unit of bandwidth decreases, is similar in principle to the "cell tax" incurred in carrying IP traffic over ATM networks due to the relatively large fraction of header (i.e., overhead) bits to data bits. In the objective function (20) we use the term where and is a constant which ensures that the two terms in the RHS of (20) are expressed in the same units.…”

“…We note that the term in (20) requires that the unit be small so as to minimize the excess bandwidth. However, making small would increase the term which represents the bandwidth wasted due to overhead operations.…”