|Issue:||North America 2009|
|Topic:||Carrier Ethernet and the new network|
Jeff Reedy is the CEO of Overture Networks, a provider of carrier Ethernet edge and aggregation solutions for business services and mobile backhaul. Prior to Overture, Mr Reedy was VP of Engineering of Larscom Incorporated, a network access equipment company. Mr Reedy joined Larscom when they acquired T3 Technologies, a start-up he co-founded. Mr Reedy began his career at Bell Laboratories designing packet switching hardware. He holds two patents. Jeff Reedy earned a BS in electrical engineering and computer science from Duke University and a MSEE from Stanford University.
Telecommunications networks are shifting from circuit switching to packet switching. This will let operators handle growing volumes of voice, image and data traffic on the same network, thereby reducing capital, operational expenses and simplify the network’s operation, maintenance and provisioning. In the past, operators retrofitted legacy voice networks with fibre optics and SONET/SDH protocols, but these networks cannot handle the growth of IP traffic. Carrier Ethernet based architectures are designed for IP-based traffic, offer gigabit speeds and can easily grow.
The telecommunications industry is in the midst of the largest transformation in history. The transition from circuit switching to packet switching has a game-changing impact upon network design and operation. At the centre of this transformation is a technology called Carrier Ethernet. Some telecom carriers may view Carrier Ethernet as just another service or interface they must add to their basket of network offerings. Others with a long-term view correctly see Carrier Ethernet as a fundamental new building block in network infrastructure that enables service providers to offer all of their key services at lower costs. Why Carrier Ethernet? Most people know Ethernet as a local area networking technology used in the office to connect computers to servers and printers and as the connection at home from the PC to the cable or DSL modem. Since the late 1990s telecom service providers and networking equipment vendors have been adapting Ethernet technology for metropolitan and wide area networks by making it more reliable, scaleable, manageable and suitable for offering multiple data, voice and video services to business customers. Why Carrier Ethernet? Over the past two decades, service providers around the world have retrofitted their legacy voice-centric networks to carry increasing amounts of data by adding the speed of fibre optics and the SONET/SDH protocols. While these technologies brought great value to the older network as traffic from data services grew, they are proving to be inadequate today as service providers are seeing Internet Protocol (IP) traffic dwarf the traditional voice traffic on their networks. This has driven the need for a fundamental change. Carrier Ethernet is the natural delivery mechanism for IP-based data, voice and video applications. It provides speeds from one megabit per second (Mb/s) to over one gigabit per second (Gb/s), and if more bandwidth is needed, it is a very quick process to ratchet up the data rate. This need for speed and flexibility touches both traditional business services and mobile backhaul. As companies increase their dependence on Internet and intranet communications, and as computing resources move to data centres and hosting sites, the network must become the enabler, not the choke point, for new ways to conduct business. In mobile communications, third generation (3G) and fourth generation (4G) applications on the mobile handset is driving a ten-fold increase in the bandwidth required for backhaul from the cell-tower to the mobile switching office. The long term It might be tempting to treat Carrier Ethernet as just another protocol or service offering one needs to add to the existing network. Operators do, in fact, leverage their existing copper and fibre assets to reach customer locations with Carrier Ethernet services, because connecting to only some of their sites is not acceptable. Despite the growth of Carrier Ethernet, other services such Frame Relay, private line, TDM, voice and IP continue to dwarf Ethernet connections today, as shown in Figure 1. Even as Ethernet takes a greater slice of the pie, these legacy services will continue to provide the majority of business connections for some time. Still, operators are beginning to embrace the notion of using Ethernet as a unifying network technology as advances in silicon technology continue to drive down the cost per bit in packet systems. Because business connections converge at aggregation points in the network, such as a co-location facility or central office, service providers are able to address the challenges posed by growing Ethernet Services while maintaining support for existing business connections. Figure 1. Business Connections in the U.S. Ideally, carriers would prefer to implement a new integrated architecture that converges all of their services using Ethernet-based technology to drive economies in switching and aggregation before hitting the network core. This architecture needs to provide quality of service across different physical media, it needs to support high levels of resiliency for non-stop operation, and it needs to support end-to-end service manageability to enable the service level agreements that businesses demand. This requires a new type of aggregation solution in the network. To date there have been two approaches to aggregation. On one hand, there have been point products that focus on a single technology or service. These point products do not scale, so they eventually reach their limits. Additionally, if there are different point products for different technologies, the operator ends up with a management nightmare. The other approach has been the big-iron multi-service edge/switch/router solution that offers every interface and protocol conceivable and can support thousands of customer connections. However, the big-iron solution has high start-up costs, carries the weight of many unnecessary features and has proven too complex and too costly to deploy in a wide-scale network footprint. What is needed is an in-between solution that combines the cost-effective pay-as-you-grow approach with the scalability of the big-iron and is optimized to bridge the circuit and packet worlds and modernizes the central office while enabling the operator to reduce costs significantly. Fortunately, service providers are receiving plenty of help from networking equipment companies and they are proactively driving requirements to advance the state of the art. In addition, service providers, enterprises and equipment vendors are all working together in standards bodies such as the MEF (formerly known as the Metro Ethernet Forum) to define feature requirements and interoperability standards that ensure networks provide the reach, scale and manageability required for a truly universal infrastructure and set of services. Mobile backhaul conundrum In many ways, the cell tower is like a business location. There are a range of services and protocols that need support and a constantly growing need for bandwidth. The second-generation systems (2G, 2.5G) prevalent today provide the basic voice communications for the cell phone. third Generation (3G) systems provide the data capabilities popular today, and fourth Generation (4G) systems will provide even greater data, voice and video capabilities. Whereas T1 and E1 connections were adequate for the earlier, voice-centric systems, the bandwidth requirements for 4G dictate a high-speed Ethernet connection between the cell-tower and mobile switching office. Figure 2. Mobile Applications Driving Backhaul Bandwidth Varying adoption rates of the newer technologies and a wide range of older handsets still in operation will force these different mobile technologies to coexist for some time. The service provider faces the problem of supporting legacy traffic and interfaces while providing high-speed connectivity for new services. As with networks built to deliver business services, it may be tempting to address the issue incrementally either by adding Ethernet to existing transport devices or by building an overlay network, but these shortsighted solutions can be costly. Adding Ethernet to existing transport systems will support legacy services and high-speed connections for 4G at the cell tower, but the traffic is still backhauled and aggregated on circuits to get back to the mobile switching office. This results in inefficiencies, stranded capacity and continued investment in legacy multiplexers and cross-connects that inhibits network scaling as packet traffic increases. On the other hand, building an overlay network to focus just on the high-speed 4G needs is even more costly since the connection to the cell tower is not shared so parallel transport and aggregation systems need to be constructed. Service providers that take the long view realize that the ideal solution is to construct a network optimized for the next generation packet services that can support legacy traffic. This can be done using a technique called ‘pseudowire’ which ‘tunnels’ the legacy traffic over the Carrier Ethernet packet network. Once legacy traffic is transformed into packets, it can be aggregated and transported along with the 4G packet traffic, taking advantage of the continually decreasing cost per bit provided by Carrier Ethernet systems. Pseudowire technology has evolved from first generation, proprietary, implementations to second generation standards-based solutions. The MEF created a set of compliance tests called MEF-18 so that carriers can verify that their solutions meet the stringent latency and jitter specifications required for circuit transport over Ethernet. Using MEF-18 compliant equipment, carriers can construct a low-cost, multi-service network that will meet all their mobile backhaul needs today and in the future. Carrier Ethernet is at the centre of the unprecedented transformation – from circuit to packet – of the telecommunications network. The applications and needs of the end user continue to expand at extraordinary rates yet the demand for quality remains high. Network designers and operators that use Carrier Ethernet strategically as the cornerstone of the new network benefit from increased revenues and lower costs and have, as well, the basis for building and maintaining a competitive edge for many years to come.