HOW TO OPERATE TRANSPORTING THE BROADBAND SURGE(英文翻译).doc

HOW TO OPERATE TRANSPORTING THE BROADBAND SURGEThe explosive growth of IP and video services, like the P2P and IPTV, are causing a dramatic spike in demand for high bandwidth in metro transport networks. OVUM RHK forecasted a CAGR of 18% and 33% respectively for the DSL market and FTTx market in the upcoming five years; while traffic in the metro transport networks would increase by 30 times. Operators now have both a challenge and a great opportunity. Making the right choice is crucial to success in maintaining customer satisfaction.Metro transport for broadband waveSuddenly, transport of mass IP services has become a priority and poses an unprecedented challenge to existing networks. A traditional metro transport network (also called a narrowband transport network) is a ring network based on the synchronous digital hierarchy (SDH), bearing voice services and small-granularity private line services. With the development of high bandwidth services, the traditional transport network is moving towards a broadband transport network that can bear IPTV and various large-granularity private line services.WDM: an essential choiceIn South Korea, the broadband penetration rate is 93% with an average speed of 49.5Mbps. Japan has 55% with 63.6Mbps and the USA clocks in with a 57% rate and a speed of 4.9Mbps. The Information Technology and Innovation Foundation (ITIF) published a report in May 2008 that showed a brisk worldwide broadband market fueled by the rapid growth of video services requiring higher bandwidth.Family broadband access is graduating from 2M to 30M or even 100M, and evolving into ultra broadband. Suppose there are 500,000 family broadband subscribers in a metropolitan area network (MAN), and the access bandwidth for each family is 30M, equaling 4010G wavelengths converged at the network core. If the access bandwidth for each family is 100M, then more than 12010G wavelengths converge at the core of the MAN. To alleviate potential bottlenecks, a wavelength division multiplexing (WDM) technology is applied to make full use of the tremendous bandwidth resources of fiber lines. In an MAN that adopts WDM technology, signals with different characteristics are transmitted transparently, and the MAN can easily bear service signals of various formats, plus save expansion costs. This had made WDM an indispensable technology for the MAN. To meet the bandwidth demands of broadband services, 4010G wavelengths need to be planned for the core exchange layer of a small and medium-sized MAN; 8010G or even 16010G wavelengths for the core exchange layer of a large MAN. The 40G transmission technology can be adopted when necessary to prevent the wavelengths from being used up.OTN: the networking WDMIn a traditional MAN, SDH is adopted for interoffice service scheduling, monitoring and protection. However, the SDH cannot be used for broadband service bearing because of its limited bandwidth and transport efficiency. Currently, interoffice service scheduling, monitoring and protection are still required in a MAN, so optical transport network (OTN) is used to satisfy scheduling and protection of large-granularity services. In a traditional WDM network, services are transported point to point and the network does not support capacity and distance expansion functions or end-to-end connection and protection functions, whereas the OTN network supports both functions. The traditional WDM network with P2P links can be developed into a highly efficient OTN network with end-to-end connection, monitoring and protection functions. This is why OTN is regarded as a networking WDM system. If WDM links are compared to information expressways where broadband services travel, then the OTN network is an overpass that joins the information expressways together into a highly efficient information expressway where the bandwidth is high and the transport is flexible.According to Zhang Chengliang, Deputy Chief Engineer of the China Telecom Beijing Research Institute, OTN technology is introduced into a WDM system in two phases. In Phase 1, OTN interfaces are introduced into the WDM system, including the line interfaces and tributary interfaces (also called inter-domain interfaces or service interfaces). After OTN interfaces are introduced into the WDM system, the performance and faults of wavelength channels in the system can be monitored end to end. With OTN technology, various client signals are transparently transported within the system, enabling the router to use 10GE LAN interfaces. In Phase 2, the OTN-based cross-connected T-bit capacity equipment is introduced into the WDM system. The equipment enhances the transport reliability of the system, achieving the quick commissioning and scheduling of large-granularity services, and optimizes the IP network structure. OTN has become the only approach for managing the system resources in the optical and electrical domains in a unified manner. With the development of broadband, tremendous wavelengths are surging over MANs. The Gigabit Ethernet (GE) and 10-Gigabit Ethernet (10GE) interfaces for large-granularity services have become mainstream network interfaces. Neither the traditional WDM technology nor the reconfigurable optical add/drop multiplexing (ROADM) technology can solve problems in the complex operation, administration and maintenance (OAM) of a multiple-granularity and multilayer network. The OTN, however, can be used for managing the services in the optical and electrical layers in a unified manner. OTN on the riseMick Reeve, the former CTO of BT, once said: “OTN will be more and more popular with operators because of the limitations of SDH and traditional WDM technologies.” Mainstream operators all over the world are now highly focused on the development and application of OTN, and WDM transmission interfaces in most networks support the OTN function. As a result, OTN has become a mainstream support technology for the backbone transport network and the metropolitan core transport layer.Development in three phases As early as in 2006, OVUM RHK accurately forecasted the development of OTN markets with the following statement: About USD3 billion of the roughly USD11 billion spent on optical networks was addressable by OTN-capable products; the opportunity will increase substantially over the next five years. Even in modest implementations, OTN offers an opportunity for network operators to capture its benefits to increase the utility and lower the cost of their evolving unified packet optical infrastructure, which is steadily outstripping the ability of SONET/SDH to efficiently manage high-bandwidth pipes.The OTN will basically develop in three phases. Phase 1: Introduction of the OTN (or Pre-OTN) with compatible interfaces. In this phase, different equipment from different suppliers supports OTN capsulation, mapping, overhead management, and forward error correction (FEC) functions as defined in ITU-T G.709. This phase began in 2005 and is largely completed.Phase 2: Introduction of cross-connect capability. This phase started in 2006 and is still underway. At the ITU Telecom World 2006 in Hong Kong, Huawei demonstrated the first WDM-based OTN system in the world: a next-generation (NG) intelligent optical transport system, called the OptiX OSN 6800/3800. By the end of May 2008, more than 5000 sets of OTN equipment have been put into stable and mature operation in networks around the world by leading operators like Vodafone, Telefonica, China Mobile, and China Telecom. Phase 3: Introduction of automatically switched optical network (ASON) and generalized multi-protocol label switching (GMPLS) to support the intelligent networking capability. As early as 2006, some leading equipment suppliers claimed that OTN would support ASON and GMPLS, and some ASON OTN networks have been put into actual operation.Broadband bears futureEquipment that supports the ASON/GMPLS control at both the optical and electrical layers has been launched on the market. ASON technology used in the WDM system is able to support higher service bearing efficiency in a more robust and reliable network. This kind of intelligent and automatic networking brings a remarkable reduction in capital expenditure (CAPEX) and operational expenditure (OPEX). Most experts in the industry believe that the metropolitan core transport network in the future will be a two-layer network formed by the IP and OTN layers. The GMPLS control plane will enable unified management of data and optical transport equipment. At the Beijing high-end transport network exhibition in May 2008, Huawei demonstrated OTN equipment with T-bit cross-connect capabilities. The equipment supports the mix of ODU1, ODU2, and ODU3 and the unified GMPLS control plane for wavelengths and ODUs. Statistics from OVUM RHK showed that the Huawei Metro WDM equipment had the highest global market share in 2007 4Q and 2008 1Q. The rapid growth of OTN is a stepping stone for operators to expand their future-oriented services. For instance, a well-known fixed network operator in Europe started constructing an NG WDM network in 2007 to shorten the development time for network broadband services. When finished, the network will be flexible and reliable enough to bear both broadband services and mass private line (including GE, 10GE, and wavelength private line) services. Because the OTN network is an open network based on end-to-end