oftware defined networking (SDN) and network function virtualization (NFV) are widely deemed two critical pillars of the future service provider network [1][2][3]. Working in tandem, these two revolutionary concepts are expected to transform the way services are created, sourced, deployed, and supported. NFV enables services to be imagined and brought to a customer in a software-only model. Software-based network functions can be rapidly instantiated, scaled, and repositioned within the network on demand and according to service policy needs. Industry standard open application programming interfaces (APIs, e.g., OpenStack, OpenNFV, OpenDaylight) allow new service variants to be created in very short innovation cycles. Network programmability enabled by SDN provides the equivalent capability for network connectivity, allowing network functions and users to be connected to deliver services in a dynamic fashion. Both concepts are imperative to significantly change the service provider's innovation cycle, simplify operations, and efficiently use network resources. This change in network paradigm is anticipated to have a positive impact on two key drivers of the service provider's bottom line: boosting revenues and reducing total cost of ownership (TCO). Total cost of ownership, in turn, has two key drivers: a) capital expense (CAPEX) for acquiring new assets and b) operating expense (OPEX) for creating, running, and delivering services to customers.The expectation for significant cost savings is frequently mentioned as one of the primary benefits of the NFV/SDN vision [2,4]. Resource pooling, multi-tenancy of applications, and the standardization of hardware platforms and middleware software indicate that substantial hardware consolidations can be achieved. At the same time, flexible placement of network functions, optimization of traffic flow through the network, and the orchestration of network resources associated with NFV/SDN all provide further intuitive indication of potential CAPEX reduction. Financial analysis indicates that yearly OPEX for service providers are typically 2-5 times higher than CAPEX [5]. This cost distribution has forced service providers to increase focus on the OPEX impact of these two new networking technologies rather than initial CAPEX outlays, leading to greater scrutiny of the annual OPEX budget. If NFV/SDN can deliver on the promise of network and service abstraction, operations simplification and automation, and hence new service creation and delivery agility, it will be an important factor in achieving the service provider goals of improved profitability.To understand the dimensions of NFV/SDN's impact on OPEX, several key topics need be addressed: Where will the OPEX reduction come from? How much reduction can be expected? What are the relative timeframes for these cost improvements? Answers to these questions will help align the service provider's expectations as well as provide direction for the operational planning and investment necessary to be ready to rapidly deploy NFV and S...
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.
Abstract. Over the last couple of years both the ATM Forum and ITU-T have converged on a closed-loop, feedback based, rate control mechanism as the framework for the Available Bit Rate ATM Transfer Capability. In this framework, an ABR source adapts its transmission rate to changing characteristics of the ATM network by either testing periodically the state of the network or through direct feedback from the network. The state of the network is conveyed to the source either as a simple binary feedback signaling congestion or no congestion, or as an explicit rate indicating the rate at which the source can transmit. In this paper we review the detailed framework for the ABR service standardized by the ATM Forum, the underlying service philosophy and protocol design goals for ABR flow control, and the premises and high-level performance characteristics for the more promising AER rate control schemes proposed so far.
The Generic Framing Procedure (GFP) is a recently standardized traffic adaptation protocol for broadband transport applications. It provides an efficiency and QoS-friendly mechanism to map either a physical layer or logical link layer signal to a byte-synchronous channel. It also supports basic client control functions for client management purposes. This article presents a brief overview of GFP.
In this paper, we describe a new protocol for framing asynchronous protocol data units (PDUs) over a general-purpose point-to-point communications channel. The generality of this protocol-we call it simple data link (SDL) protocol-allows it to be used to transport most PDU types, such as IP/IPX datagrams, 802.3 frames, and ATM cells. Its low implementation complexity makes it particularly suitable for high-speed transmission links such as SONET/SDH point-to-point links, SONET/SDH paths, 1 and wavelength links in an optical network. Point-to-point transmission links deliver the incoming information stream in a sequential and orderly fashion, which greatly simplifies frame boundary delineation and recovery procedures at the SDL layer.While the focus of this paper is on the primary function of SDL-to provide PDU framing and delineation-we have designed SDL to facilitate many traf-♦ A Simple Data Link Protocol for High-Speed Packet Networks Bharat T. Doshi, Subrahmanyam Dravida, Enrique J. Hernandez-Valencia, Wassim A. Matragi, M. Akber Qureshi, Jon Anderson, and James S. Manchester Many popular point-to-point data link protocols use the high-level data link control (HDLC) framing mechanism, which delineates protocol data units (PDUs) by means of a special bit pattern or flag. When such a flag occurs in the payload portion of a frame, an escape byte used to pad the transmitted byte stream enables the receiver to differentiate between a true framing flag and an occurrence of the flag pattern in the user information. The need to process each byte in the incoming byte stream to identify the flag pattern makes this frame delineation method increasingly more complex and expensive to implement as the interface speed increases. In addition, the byte stuffing operation performed when the flag pattern appears in the user information stream expands the carried traffic, interfering with quality of service (QoS) management procedures and making the link susceptible to malicious attacks. These factors limit the scalability and QoS management capabilities of the flagbased data link protocols, particularly at high link rates. The increasing popularity of the packet over SONET (POS) protocol stack makes it desirable to find alternative framing protocols. In this paper, we present a simple data link (SDL) protocol. Based on using a Length Indicator field and a header cyclic redundancy check (CRC), rather than a flag, to delineate frames, SDL is inherently scalable to high speeds and provides constant transmission overhead. We discuss the error control, delineation, and resynchronization mechanisms used by SDL, and we describe a link scrambler designed to protect against malicious attacks that attempt to generate very low bit transition density on the line. We also present additional link control functions designed to make SDL suitable for next-generation multiservice networks.86 Bell Labs Technical Journal x January-March 1999 fic engineering functions needed in the next-generation multiservice packet networks. In particular, w...
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