Building Next Generation DSL Networks with the Redback Service Gateway

Building Next Generation DSL Networks with the Redback Service Gateway Providers must respond to the growing adoption of DSL by building an advanced architecture that supports a diversity of services, users, and devices. Redback's Service Gateway enables providers to deliver the next-generation broadband architecture to competitively offer value added services to subscribers. User Intelligent Networks White Paper

Redback Networks White Paper Executive Summary As DSL adoption grows around the world, so does its strategic importance to service providers. Providers are relying on DSL as an additional revenue stream, a competitive differentiator, and a means of protecting their voice franchise with existing customers. As a result, DSL services must go beyond simply providing Internet access and data services and evolve into more advanced offerings. At the same time, the market for DSL users is changing as business users adopt DSL more aggressively and a large variety of end devices such as set-top boxes, Wi-Fi access points, and IP phones are used for DSL connectivity. Service providers must build a next generation DSL architecture to respond to these trends in the DSL networking industry. This architecture must support these requirements: Higher bandwidth per user Quality of Service for traffic Support of multiple technologies such as MPLS and multicast Support of multiple end devices such as settop boxes and IP phones Extension of existing Authentication, Authorization, and Accounting system to support new services and device types Diversity of new networking technologies both downstream and upstream of DSLAMs Integration of Application Service Providers (ASPs) offering third-party content and services Redback Networks has introduced the SmartEdge Service Gateway platforms to enable DSL providers to address these trends and build a next generation architecture. The Service Gateway feature set is available as a software upgrade on the SmartEdge 800 and 400 hardware platforms. The defining characteristics of the Service Gateway are: Simultaneous support of multiple applications at line-rate performance Subscriber configurability based on Redback s proven SMS technology Advanced Quality of Service (QoS) capabilities High performance and scale Extensive support for unicast and multicast routing, and MPLS services Flexible form factor The Service Gateway provides numerous business benefits for DSL providers. One of the most important benefits is that the Service Gateway supports services that both add competitive advantage and increase margins, such as virtual private networks (VPNs), bandwidth on demand, and streaming content. Providers can also save costs by integrating multiple applications on to a single device, eliminating unnecessary equipment costs. Even if providers choose to dedicate a Service Gateway for a specific application, they can still save in spare parts and operational costs, as personnel are trained on only one platform. As a final benefit, DSL providers can use the Service Gateway to migrate to a next generation architecture while using existing infrastructure. Introduction Broadband access has grown considerably in the last few years, with DSL comprising a large fraction of this growth. According to the research firm Point Topic, the number of DSL connections around the world has grown from under 1 million at the end of 1999 to over 35 million at the end of 2002. Cable modem usage has grown from about 4 million to 24 million connections in this same period, and there are about 3 million users with Internet access over Gigabit Ethernet, making a total of about 63 million users at the beginning of 2003. Figure 1: The worldwide adoption of DSL from 1999 until 2002 DSL s rapid growth is causing an impact on the financial statements of telecommunications companies around the world, as the revenues and margins associated with DSL services become significant. It is therefore becoming a strategic priority for telecommunications service providers to be competitive about offering DSL services that add customer value and are both easily provisioned, and attractively priced. To accomplish this goal, providers must have an infrastructure in place that can support DSL services and be easily upgraded when demand for new services appears. Although standard Internet access has been the predominant reason for DSL adoption, more advanced services will eventually drive DSL demand. Providers must prepare for this inevitability by building a service-capable infrastructure. Redback Networks has developed the SmartEdge Service Gateway platforms to assist providers in building next generation DSL networks. The Service Gateway feature set is available on the SmartEdge 800 and 400 hardware platforms as a software upgrade and can be readily added to an existing network to support services currently in demand as well as future services. 2

Building Next Generation DSL Networks with the Redback Service Gateway This white paper describes the defining attributes of the Service Gateway and its business benefits. To provide the proper context, this paper first explores the business trends in the DSL networking industry that have created the need for a Service Gateway. The next section describes the technical requirements for the next generation DSL architecture that form a response to these trends. The paper then explores the Service Gateway itself and how it directly addresses the technical requirements of the prior section. To assist in understanding the value of the Service Gateway, this white paper discusses the current state of deployed DSL networks and how the Service Gateway enables providers to upgrade their existing infrastructure to a next generation architecture. Finally, the business benefits of the Service Gateway are enumerated. Greater service proliferation The DSL market has so far been characterized by a rapid build-out of services providing simple Internet or data access. However, reaction from competitive pressures or a desire to expand the usability of DSL is driving many service providers to consider more advanced network-based or content-based services that differ from their traditional core competencies of voice and data services. Examples of these services being deployed successfully over DSL networks around the world include gaming, network-based backup and storage, content filtering, music services, and network-based firewalls. These services have the potential of delivering greater margins than traditional data services and can also be used as a competitive differentiator against other DSL providers or cable or satellite service providers. Major Trends in DSL Networks There are presently a few major trends in the DSL networking industry that are driving the evolution of the technical and business strategy of service providers: Strategic importance of DSL DSL is becoming increasingly strategic to many telecommunications providers, particularly ILECs, PTTs and IXCs. As discussed in the introduction, there were 36 million DSL subscribers worldwide at the end of 2002, almost double the number at the end of 2001. In addition, as broadband access around the world continues to be adopted, providers are relying on DSL not only as a revenue stream and a source of higher margin services but also as a vehicle to retain their traditional voice franchise. This is especially true because of the development of competing voice over IP or voice over cable technologies. North American cable companies, for example, have been successful at offering both video and data services over the same connection and are aggressively testing and deploying voice services as well. DSL providers must offer competitive and value-added services to protect their market share and further increase their accessible markets. In addition to offering voice over DSL to guard against other providers offering broadband voice services, DSL providers must also consider broadband TV and video-ondemand to compete directly with traditional cable and satellite broadcast TV service. The end goal of many providers is "Triple Play," which is the combination of voice, video, and data over a broadband connection. Figure 2: The triple play concept: Voice, video, and data on a single connection Figure 3: Advanced services offer higher margins and greater subscriber retention Diversity of end users and end devices One of the final trends in broadband networking is the increasing diversity of both end users and end devices. More and more DSL customers are enterprises, using the DSL connection as either a less expensive substitute for a leased line or for telecommuting employees. This is especially the case in Asia where access speeds are higher because of VDSL, fiber-based local loops, and other high bandwidth access technologies. Business users have their own distinct needs for services such as VPNs that will seamlessly connect them to their corporate networks. There is considerable overlap, however, between residential and business customers as they both demand services such as video streaming, voice, and firewalls. There is also an increasing proliferation of end devices. While a PC or a home router has been the traditional end device, the takeoff of home networking technologies and Wi-Fi has changed this considerably. End devices capable of delivering broadband service now include a set-top box, a PDA, an IP phone, an intelligent home gateway, or a Wi-Fi access point. This diversity of end devices further increases the type and number of services that can be offered, as the diverse capabilities of each end device allow for services that are individually tailored to them. 3

Redback Networks White Paper Support of multiple technologies As indicated in the previous section, the increasing diversity of end users and end devices requires an array of different technologies. For example, business DSL users must be granted seamless access to corporate VPNs with technologies such as MPLS or be protected from Denial of Service (DoS) attacks. Multicast is also a requirement for the streaming of high bandwidth media content. Figure 4: Both business and residential users use varied end devices for DSL connectivity Requirements of Next Generation DSL Networks DSL providers require an infrastructure that is capable of responding to these trends and enables them to offer competitive services that will increase market share and expand the DSL market. Some of the requirements for this infrastructure are: Higher bandwidth per user Underlying all of these services is an infrastructure capable of guaranteeing the delivery of network traffic. Especially as video services are offered across a DSL connection, bandwidth requirements per subscriber increase dramatically. Both MPEG-2 and MPEG-4 video encoding require at least 1 to 2 Mbps per stream, with even more bandwidth needed for higher resolution. Peer-to-peer file sharing services also involve the transfer of large files. Accompanying higher bandwidth may be a "turbo button" or "bandwidth on demand" feature, where DSL customers may temporarily have more bandwidth available to them in order to access video or other large downloads. Once the content transmission has completed, the customer s bandwidth is reduced to the normal amount. Tiered bandwidth may also be an option, where a customer elects to permanently upgrade his consumption level. Quality of service Equally critical as higher bandwidth per user are the QoS mechanisms required to control the latency and "jitter," or the variation in latency, of traffic. Some applications such as gaming or voice require very low or predictable traffic latencies. Too much latency or jitter will cause a service to be unusable, i.e. the game player keeps losing due to control packets not arriving on time or a voice session is incomprehensible due to voice packets not arriving on time. Support of multiple end devices The different end devices such as IP phones, set-top boxes, etc. may require their own specific enabling technologies. One example involves PPP over Ethernet (PPPoE). Some end devices may not support PPPoE clients, which is the standard way of accessing DSL services. Therefore a clientless method of connecting with the network is necessary. Extension of existing Authentication, Authorization, Accounting (AAA) system New services must be easily accessible by customers and seamlessly integrated with a provider s Authentication, Authorization, and Accounting (AAA) system. This AAA system enables services for customers and tracks service changes for billing purposes. The most common method of enabling services for customers is a self-provisioning Web portal. After a customer signs up for a service, the Web server must communicate with the services infrastructure to enable this service for the customer. The billing system must be updated in parallel so that any updates can be billed appropriately. The AAA system must also support per-subscriber attributes such as bandwidth limits, prioritized traffic settings, and multicast group membership entitlement. As each subscriber authenticates and initiates a session, these attributes are loaded and used for the duration of the session or they could be applied when a new session is added. Finally, the AAA system needs to take into account various access technologies, especially Wi-Fi with its surging popularity and the proliferation of wireless "hot-spots" in public areas. Wi-Fi support will enable providers to package broadband access to an expanded group of customers. Figure 5: Too much latency or jitter adversely affects a DSL subscriber session Figure 6: Web server communicates service and billing information to AAA server 4

Building Next Generation DSL Networks with the Redback Service Gateway Diversity of physical and logical networking technologies In addition to Wi-Fi, DSL providers must support a wide range of physical and logical access technologies to more easily enable both consumers and businesses to use DSL. Another prominent example of a widespread access technology is Ethernet, particularly in dense urban areas. Upstream of the DSLAM, providers must also be flexible in what networking technologies they support. Although ATM is the predominant technology for the aggregation of DSLAMs, ATM has scalability and bandwidth constraints. Alternative technologies, especially Gigabit Ethernet, MPLS, and IP must be considered in conjunction with ATM because they offer greater bandwidth and flexibility. This is especially critical because of the increased bandwidth requirements of some new services. Figure 8: DSL provider enables end customers to easily connect to ASPs Delivering Next Generation DSL Networks: Redback s Service Gateway Platforms To meet the needs of providers who wish to build next generation DSL networks, Redback has upgraded its SmartEdge 800 and SmartEdge 400 products to function as Service Gateways. The Service Gateway is defined by these important attributes: Simultaneous support of multiple applications One of the most important attributes of the Service Gateway is its ability to support multiple applications simultaneously with linerate forwarding performance. These functions include subscriber management, VPNs, IP routing, ATM mediation, multicast, and QoS. The functions can also be combined, so broadband subscribers are granted seamless access to VPNs or subscriber traffic is prioritized, or rate limited by QoS mechanisms. This simultaneous support of applications is an effective response to the merging of residential and business DSL requirements, as both customer types can be terminated on the same device. Figure 7: DSLAM aggregation network may rely on Ethernet or MPLS for greater bandwidth and flexibility Integration of Application Service Providers In order to increase the amount of total content available to DSL customers, providers must enable third-party content or service providers, also known as Application Service Providers (ASPs), to easily communicate with DSL end customers. Each ASP provides content such as video or a service such as storage or gaming. The DSL network therefore serves as transit between end customers and multiple ASPs. To facilitate this process it is also necessary to develop standard interfaces between ASPs and DSL providers, so that it is straightforward for ASPs and DSL providers to interconnect. They do not have to spend extra time or energy in designing and supporting proprietary interconnection schemes. This concept is very similar to the existing practice of wholesaling between DSL end customers and retail ISPs, where the ISPs sell Internet access and other data services directly to the end customers of DSL providers. DSL providers usually use L2TP or another standardized protocol to tunnel subscriber traffic through their networks to retail ISPs. The Service Gateway s simultaneous support of multiple applications is made possible by its innovative software architecture. Designed from the ground up for 99.999% or fivenines reliability and flexibility, the operating system is based on a multi-processing kernel with each major component implemented as a separate process with its own memory space. Multiple processes can all run independently, where each can be stopped, restarted, and upgraded without affecting the others. Figure 9: Simultaneous support of multiple applications Subscriber configurability Redback leverages the proven technology of the market-leading SMS subscriber management systems to provision, manage, and aggregate DSL subscribers. The Service Gateway relies on a proven AAA technology, RADIUS, to authenticate subscribers and act as a Broadband Remote Access Server (B-RAS). One of the 5

Redback Networks White Paper primary benefits of RADIUS is its extensibility, as new attributes can be added to subscriber profiles. The Service Gateway can easily support different access methods and end devices, as well as new services, by adding new RADIUS attributes. For subscribers that do not use a PPPoE software client, the Service Gateway supports Clientless IP Service Selection (CLIPS). Though the use of PPPoE clients is prevalent in the DSL industry, many newer devices do not use them. CLIPS is therefore crucial to the support of new end devices. CLIPS is also necessary in network architectures where PPPoE is either not supported or not preferred. As a subscriber is authenticated to the Service Gateway, the RADIUS attributes from the subscriber s profile are loaded into the device and used to configure the appropriate services. RADIUS information is sent to the provider s billing system as well. A subscriber may also use a Web portal to modify his subscriber profile and change service parameters, such as the tier of bandwidth or the priority of certain applications. After a profile is updated, the change can take place immediately as the subscriber is re-authenticated and the new attributes are loaded. Figure 10: Service Gateway loads subscriber attributes from RADIUS server Advanced QoS capabilities The Service Gateway s extensive QoS capabilities help ensure the effective delivery of traffic, as both latency and jitter are minimized with the marking and policing of packets. These capabilities are essential for the support of certain applications such as voice or gaming. These QoS features are also used for tiered bandwidth and bandwidth on demand applications. High performance and scale The Service Gateway is capable of supporting all of these functions while forwarding traffic at line-rate. The SmartEdge 800 platform can forward traffic at 160 Gbps or 65 Mpps. Each subscriber can access a very high level of bandwidth, even up to the 40-50 Mbps that VDSL customers receive. The Service Gateway can also reach a high level of scaling in multiple areas. It can support between 32,000 to 40,000 active subscribers on a single chassis, with 2,500 VPNs and a multicast fan-out of up to 100,000 receivers. Extensive support for unicast and multicast routing and MPLS services The Service Gateway delivers a complete set of unicast routing protocols including BGP, OSPF, IS-IS, and RIP, and a suite of multicast protocols used for content delivery and other streaming applications. The Service Gateway supports Layer 3 and Layer 2 MPLS VPNs, as well as L2TP, all relying on industry standard protocols. This extensive VPN support facilitates the integration of thirdparty content providers. An MPLS VPN or an L2TP tunnel is provisioned to each content provider, enabling end users to directly access content hosted off of the DSL provider s network. Flexible form factor The Service Gateway is available in a variety of form factors for different applications. The SmartEdge 800 platform is optimized for use in Points of Presence (POPs, supporting functions such as leased line termination, subscriber management and VPNs. The SmartEdge 400 platform is optimized for use in the Central Office (CO) because of its smaller form factor. It is ideal as an upstream gateway for DSLAMs, providing the uplink bandwidth to the DSLAM aggregation network. DSL providers can therefore preserve their considerable investment in the existing DSLAM infrastructure and seamlessly enable their network to support new services. The SmartEdge 400 platform also performs service insertion where multicast replication and QoS functions are performed at the CO rather than the POP. This concept of service insertion is explored further in the next section. Using the Service Gateway in Currently Deployed DSL Architectures DSL providers must ensure that their existing infrastructure can meet the requirements for next generation broadband networks. In some cases, they face challenges because certain aspects of their architecture cannot be easily modified or upgraded. This section explores these challenges and how the Service Gateways help providers in addressing them. Clear separation between residential and business services Providers generally separate residential services from business services. In many cases, completely different groups with very different operational models handle them. The revenue per user is typically much higher for business services and as such carriers do not want to mix the two. For example, Service Level Agreements (SLAs) are usually only associated with business services. However, as explained in the section on broadband trends, there is an increasing overlap between residential and business customers as they both demand services such as content delivery, firewalls, and voice services. At some point it makes 6

Building Next Generation DSL Networks with the Redback Service Gateway financial sense to consolidate residential and business services on the same hardware. The Service Gateway enables this by supporting multiple applications on a single device. Even though there are operational issues associated with this consolidation, there are significant cost advantages derived from reducing the number of devices and reducing capital and operational expenses. And even if residential and business services continue to be supported by different groups on separate hardware, providers may still save costs by deploying the same platform in both groups. This will save management and equipment costs, as the operations personnel are trained on a single platform and only need to use one provisioning system. Also, spare parts for only one system need to be retained. Despite these limitations, providers have made significant investment in their ATM-based DSLAM network and will not move away from this investment quickly. An alternate solution to replacing the DSLAMs is to supplement them with the Service Gateway. The Service Gateway is colocated inside the CO with the DSLAMs and performs a variety of functions. First, it provides the uplink bandwidth to the rest of the aggregation network, which is based on a transport technology like Gigabit Ethernet or MPLS. Figure 13: Service Gateway provides Ethernet or MPLS uplinks for legacy DSLAMs Figure 11: Consolidation of residential and business services on same hardware Entrenched DSLAM deployment Within the CO, the DSLAM is the most important network element required for DSL service. Although a DSLAM is a simple device with limited network functionality, DSLAMs still vary by geographic region. For example, in North America and parts of Europe, DSLAMs are mainly ATM-based where each DSLAM has an ATM uplink to a regional network aggregating all of the DSLAMs into a POP. In Asia and other parts of Europe, DSLAMs tend to be based more on Ethernet, particularly with newer DSLAM or VDSL deployments. ATM-based DSLAMs provide constraints on scalability and bandwidth, and often lack the capability to support advanced IP services. For example, bandwidth is capped at 622 Mbps (OC-12). Multicast content replication over an ATM network can be difficult because of this limitation, as a 2 Mbps content stream could only be replicated 300 times for subscribers. Also, any QoS between the B-RAS and the DSLAMs must be based on ATM cells. This restriction prohibits the more granular marking and identifying of application-specific traffic, which IP QoS allows. Figure 12: Multicast replication to DSLAMs can be overly bandwidth intensive for an ATM network The Service Gateway also provides service insertion functions for subscribers. Multicast content can be replicated closer to the edge of the network, conserving bandwidth within the DSLAM aggregation network and providing a higher degree of replication for each DSLAM. IP QoS can now be performed within the CO, allowing traffic to be treated differently by application between the B-RAS and the DSLAMs. Figure 14: Service Gateway provides multicast replication and IP QoS closer to network edge Business Benefits of the Service Gateway Redback s Service Gateway platforms have numerous tangible business benefits for providers offering DSL services: Increased revenue and profit through new services One of the most important business benefits of the Service Gateway is to enable services that both add competitive advantage and increase margins. Both network-based services 7

Redback Networks White Paper such as VPNs or bandwidth on demand and content services such as video streaming are available for both residential and business DSL customers. Save costs by integrating multiple functions on to a single platform The Service Gateway is capable of supporting many functions simultaneously with line-rate forwarding, including DSL subscriber management, leased line aggregation, VPNs, and Quality of Service. Providers can consolidate equipment and save in capital expenses by running multiple applications on a single device, where multiple devices would otherwise be required. This is especially advantageous in smaller POPs where it is not costeffective or space-efficient to support multiple devices. If providers choose to dedicate a Service Gateway for a specific application, they can still save in both capital and operating expenses. They only need to deploy a single platform throughout an entire geographic area, eliminating any costly guesses as to which equipment is installed at which site. Spare parts costs are minimized because parts for only one platform need to be kept on hand. Operational staff need to be trained on just one device, lowering training costs. Finally, a management system can support the Service Gateway for multiple applications, eliminating costly modifications that are often made to a management system to support applications based on new hardware platforms. Enable phased network migration to support services DSL providers can use the Service Gateway to enable a phased network migration to support services, thereby preserving their initial capital investments and avoiding service-disrupting equipment upgrades. Providers with entrenched DSLAM deployments may upgrade their DSLAM aggregation network or provide content or service insertion by simply putting a Service Gateway into the CO to supplement the DSLAMs already colocated there. There is no need to replace these DSLAMs, and each DSLAM may be connected to the Service Gateway one at a time to minimize service disruption. Improve network efficiency with multicast streaming One of the primary benefits of multicast technology is to conserve bandwidth while streaming content throughout a network. Multicast builds a "tree" to avoid content duplication and then performs the replication of content only at the very edge of the network. The Service Gateway excels at multicast distribution and is able to replicate traffic up to 100,000 times for content receivers at the edge of the network. Colocating a Service Gateway within a CO provides optimal multicast efficiency and helps providers to minimize bandwidth costs that would otherwise be spent on content distribution. 8

Building Next Generation DSL Networks with the Redback Service Gateway 9

User Intelligent Networks Summary As DSL increases in strategic importance and the demand for more advanced services is accompanied by a greater diversity of end users and end devices, service providers must respond by building next generation DSL networks. Redback has developed the SmartEdge Service Gateway platforms to assist providers in developing their advanced DSL infrastructure. It is capable of supporting numerous applications simultaneously and is available in multiple form factors, enabling a wide variety of services and helpful in migrating existing networks to a next generation architecture. The Service Gateway provides additional revenue in the form of advanced services and minimizes both capital and operational expenses. For further information SmartEdge Service Gateway Product Marketing ask-marketing@redback.com North & South America Corporate Headquarters 300 Holger Way San Jose, CA 95134-1362 USA Tel: +408 750 5000 Fax: +408 750 5599 Europe, Middle East & Africa EMEA Headquarters Max Euwelaan 61 3062 MA Rotterdam The Netherlands Tel: +31 10 498 77 66 Fax: +31 10 498 77 88 Asia Pacific APAC Headquarters Rm 1615, 16/F China Merchants Tower Shun Tak Centre 168-200 Connaught Road Central Hong Kong, China Tel: +852 2587 8832 Fax: +852 2587 7119 www.redback.com Product Specifications are subject to change without notice. REDBACK and SmartEdge are trademarks registered at the U.S. Patent & Trademark Office and in other countries. SMS and NetOp are trademarks or service marks of Redback Networks Inc. All other products or services mentioned are the trademark, service marks, registered trademarks or registered service marks of their respective owners. 2003 Redback Networks Inc. All Rights Reserved. RB-WP-SG-0803