Integrated Access Devices (IADs), which traditionally served Small to Home Office (SoHo) and Small to Medium Enterprises (SME), are beginning to play a significant role in next-generation network evolution. Many service providers, including major telcos, who recognize the need to provide integrated services to homes, are re-engineering IADs to operate as Residential Gateways. Residential gateways are critical systems that will enable service providers to deploy new, profitable services to homes and reduce churn.
As core infrastructure is being upgraded to facilitate deployment of innovative, converged services, the boundary between service provider network and residential subscriber is rapidly blurring. Residential broadband connectivity has evolved significantly over several years while service providers kept an eye on increasing average revenue per user (ARPU) during a phased service integration. At the heart of this evolution is the vision of the
"digital home", which offers service providers an opportunity to generate additional revenue through bundled services and associated service level agreements. No longer is broadband connectivity limited to a simple modem. Today's digital home requires various devices that are influencing the way the modem has evolved over time.
As users migrated from a single computer to multiple PCs in the home, the modem became a router. The advent of 802.11-enabled mobile computers further transformed the device into a wireless router. With the advent of
VoIP, advanced techniques for Quality of Service (QoS) and traffic management had to be incorporated to ensure voice quality and to connect analog end-user equipment. Now emerging next-generation core transport network architecture, such as IP Multimedia Subsystems (IMS), is leading to convergence of cellular service and packet-based services. As a result, consumers will experience converged fixed and mobile services that move seamlessly between cellular infrastructure and packet-based VoIP infrastructure inside home.
In addition to fixed-mobile convergence is the deployment of true triple play services, in which service providers deliver voice, data and video content, including Video on Demand service and IPTV services. These new video services over IP infrastructure within the home also includes subscriber oriented networked Personal Video Recording (nPVR) service deployment.
With all these new demands, the basic modem has transformed itself into a truly integrated residential converged gateway that is central to the service provider vision for delivering next-generation services. In addition to enabling voice, data, video and fixed-mobile convergence, the residential gateways must offer a high level of security to maintain the integrity of all content.
A Degree of Complexity
The demands of the digital home are requiring residential gateways to become more complex in order to ensure flexibility for the service provider. Service providers are deploying various last mile access technologies that differ in bandwidth and reach. These access technologies deliver downstream bandwidth at speeds of less than 24 Mbps, in the case of ADSL2/2+, up to 2.4 Gbps using VDSL2 EPON and GPON (Passive Optical Networks). As a result, residential gateway systems must be able to scale to accommodate these access technologies while routing IP packets between the provider network and networked end terminal devices in the home.
The in-home content distribution networks are equally as critical for the residential gateways. A wireless environment is supported primarily by 802.11a/b/g/n. However there are a number of different in-home, wired content distribution methods. These methods include power line (Homeplug), copper phone line (HomePNA) or coax cable (Multimedia over Coax, or MOCA). With the growing popularity of VoIP, residential gateways also must integrate call establishment technologies like Session Initiation Protocol (SIP), H.323, Media Gateway Control Protocol (MGCP) and Megaco. And finally, residential gateway technology must support a varying number of voice ports and types of voice compression algorithms.
In addition to these key connectivity and voice technology components, residential gateways must address complex QoS and traffic management requirements at multiple levels -- Layer 2 bridging and Layer 3 routing -- in order to deliver high-quality video content. In order to meet future demands for media storage, particularly for nPVR services, gateways need to provide different storage options with associated content management software features.
With the addition of so much content riding through the residential gateway, service providers need to have a well-defined security framework. Residential gateways must incorporate packet encryption/decryption technologies, such as Advanced Encryption Standard (AES) or Data Encryption Standard (DES), and key exchange mechanisms Internet Key Exchange (IKE). Residential gateways also must support Virtual Private Network (VPN) termination (IPsec), VPN at the application layer (Secure Sockets Layer, or SSL), deep packet inspection technology to enable Intrusion Detection Services (IDS) and advanced firewalls. These security features have implications on both the hardware content and system software content of the residential gateway.
Perhaps the most critical requirement for any residential gateway is the device's ease-of-manageability. Auto configuration, remote configuration and management for guaranteed service delivery and compliance to service level agreements must be incorporated since residential gateways are central to a service provider's vision for successfully delivering IP services. To manage residential gateways effectively and ensure reliable service delivery, vendors need to integrate a management framework like the DSL Forum's TR 69.
It is also essential that design and development investments made in software and hardware can be leveraged across different access networks -- including ADSL2/2+, VDSL2, EPON and GPON.
A processor architecture that can scale across such wide bandwidths without sacrificing switching and routing performance for wired and wireless interfaces as well as secure and non-secure data flows enables system designers to future proof gateway products. Considering that different applications will be integrated into each residential gateway, a flexible architecture that incorporates advanced QoS and traffic management engines with a provision for dynamic changes into policies ensures that the system is capable of guaranteed delivery for time sensitive services like VoIP, VoD, IPTV and gaming.
The evolution of requirements for residential gateways poses a challenge to system design, which calls for flexible and scaleable gateway processor architectures. Today's residential gateway processors are fast becoming a nodal component in which multiple application services, network routing, data security, storage and in-home content distribution network interface technologies are converging. As a result, a unique data flow architecture is needed to ensure that future application can be seamlessly integrated into residential gateway processors.
The IP Services Delivery System Model
Residential gateways are central to overall IP services delivery to digital home. As such, it is important that systems designs allow flexibility so as to meet key requirements for current services while being adaptable to support new services and scalable to handle increased bandwidths. The first generation packet routing residential gateway systems were built around general-purpose processors. They had single plane architectures in which packet processing functions, control software, and specific service agents all resided on a central processor.
That architecture, however, is not well suited to handle challenging traffic conditions, such as wire speed packet switching. For example, a device that can route 100 Mbps of traffic with large packet sizes may struggle to switch 10 Mbps of small packets. This requirement is very critical considering different applications call for different sizes of packets and in many cases small, transaction-oriented packets are time sensitive.
General-purpose processors and network interface controller architectures are not suited for higher traffic conditions because most of the processing required to achieve the packet routing functionality is carried out in software running on the processor. General purpose processors are designed for general computing environments. A large number of cycles are spent on tasks that are not connected with packet processing. As the traffic rate increases, the time between packets reduces. The processor now has to perform the same function in less time. Further complicating matters is the need to deal with deep packet inspection in order to meet security requirements, in which QoS needs to be ensured for different classes of packets, and for multicast distribution of video content.
While increasing the processor speed does help, it does not solve all of the problems. The reason:
the processor is not only handling the routing function, but also performing the rest of the software responsibilities in the system, including customer-driven application processes, and control plane activities like management and operating system functions. Additionally, the demand on processing power by newer services is difficult to predict. A multi-plane model allows for the packet processing acceleration needed for higher last mile access bandwidths. They also allow for a dedicated service plane in which dedicated engines support target services, while a central processor supports control and management functions.
With advanced functionalities like Network Address Translation (NAT), Packet Filtering, Stateful Firewall and VPN offered by the newer breed of gateways, the amount of processing required for every packet has increased greatly. With the traditional processor-based approach, it is not possible to design a gateway that can meet the increased requirements. This data flow architecture requires the separation of control and application agents from the actual data forwarding path. The following section explores a different approach using a multi-plane architecture that addresses this specific need.
Figure
1 -- Conceptual multi-plane
The above framework employs fast path processing thereby offloading the main CPU, and results in a scalable solution.
System and Functional Blocks
Figure
2 -provides a layered model for the software modules that are integral to
Residential Gateways.
From the core functionality standpoint, current and next-generation residential gateways must support a number of key features. These features include:
Control Operating System
-- The industry is increasingly moving towards open architecture embedded Linux operating system. However depending on past development experience and in-house expertise other real time operating systems also are in vogue.
Voice Infrastructure
-- This includes voice-specific ITU G series compression and decompression technologies (G.711, G.729 etc.) combined with echo cancellation implementations and different voice specific algorithms like tone detection, comfort noise generation and adaptive jitter buffer mechanisms.
Call Establishment Technologies
-- Service providers have considered different technologies depending on what their core infrastructure supported . However recent initiatives like IMS is driving SIP as the key call establishment technology.
QoS -- This is a functional requirement that plays a central role in delivering IP services to subscriber. Flexibility and configurability is the key. QoS functions need to be implemented at different layers including physical layer, medium access and link layers, as well as the networking/routing layer. These technologies include Diffserv, IEEE 802.P/Q, Virtual LAN specific bandwidth provisioning and IEEE 802.11e, and the QoS framework in 802.11 wireless networks.
Multicast Support -- This is essential for delivering emerging VoD and IPTV services.
Security
-- This is another critical residential gateway functional block. There are various levels of functional blocks that need to implemented . Residential Gateways have now truly become a converged system where last mile wide area communication interfaces, inside home network interfaces and wireless interfaces are converging. All packet communications on these interfaces pose potential threats to content and data integrity. As a result various levels of security framework must be integrated. Security value chain includes Network Address Translation (NAT), firewalls including state-ful implementation, access controls, IPsecurity VPN, Secure Socket Layer VPN, Deep Packet Inspection (DPI) functions to implement Intrusion Detection and Prevention functions, wireless security framework that includes Wi-Fi Protected Access (WPA) and IEEE 802.1x authentication process.
Storage Interface and Associated Content Management Software
-- This functional block enables implementation of networked PVR service in a digital home connected with multiple set-top-boxes.
System Management Software
-- This is needed to support integrated remote management, configuration and traffic monitoring functions that help ensure compliance with Service Level Agreements. Several management frameworks are in place and among them DSL Forum TR 69 is fast emerging as one of the key technologies for remote management. This framework also provides a management model through which network operators can effectively manage in-home terminal systems that are connected to a residential gateway. Wireless channels must also be managed since wireless home networks could be used for video content delivery.
Residential gateways have become more complex and are enabling service providers to effectively deliver next-generation services, thereby effectively increasing ARPU. Different access technologies combined with various integrated in-home wired and wireless network technologies are resulting in the development of residential gateway system hardware that is flexible enough to meet future service deliver needs.
About
the Author
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Sanjeev Challa is chief technologist in the Gateway Products Group at Ikanos Communications, where he is responsible for guiding the development of next-generation broadband gateway architectures and triple play service integration. Most recently, Mr. Challa served as product line director of the Broadband Business Unit of Analog Devices, which was acquired by Ikanos from ADI in February 2006. In this role, he headed the broadband business unit, overseeing development of the Fusiv architecture and Vx series of gateway processors. Prior to that, he served as director of Engineering in ADI's Communications Processor Group.
Before joining ADI, Mr.
Challa was vice president of Engineering and Chief Technology Officer at
Chiplogic, a start-up engaged in developing broadband gateway processors
for integrating data switching, security and VoIP service in the
residential and SME markets. Chiplogic was acquired by ADI in 2001. Prior
to Chiplogic, Mr. Challa was general manager-technical for Wipro
Technologies USA, where he was instrumental in developing IP routing and
ATM switching equipment for enterprise and carrier customers.
Mr. Challa earned a B.S. in
Electronics and Communication Engineering at the Regional Engineering
College in Warangal, India and an M.S. in Electrical Engineering from the
Indian Institute of Technology in Bombay, India.
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About
Ikanos
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Ikanos
Communications, Inc. (NASDAQ: IKAN), develops chipsets that enable
carriers to offer Fiber Fast™ bandwidth and high-speed network
processing for enhanced triple play services. Supporting
transmission rates of up to 100 Mbps, Ikanos' line of end-to-end
silicon solutions power line terminals, CPE modems and
residential gateways for many of the world's leading network
equipment manufacturers. Ikanos' solutions enable fast and
cost-effective carrier rollouts of interactive broadband services
including IPTV.
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