Cisco® Service Exchange Framework provides a set of enabling technologies that support open application program interfaces (APIs) and operate nearly transparently with third-party policies and services. The Cisco Service Exchange Framework supports Telecommunication and Internet Converged Services and Protocols for Advanced Networking (TISPAN) standards while providing support for a broad range of services and applications required by residential and business subscribers.
Abstract
TISPAN is a body within the European Telecommunications Standards Institute (ETSI). TISPAN's role is to develop a service-delivery architecture to adapt the wireless Third-Generation Partnership Program (3GPP) standards to address the needs of wireline providers who are looking to increase the monetization of their IP transport networks.
TISPAN is embracing and extending the service delivery concept originally designed for the wireless-centric IP Multimedia Subsystem (IMS) to include the Public Switched Telephone Network (PSTN) Emulation Subsystem (PES) along with other service subsystems for wireline environments. While support of non-IMS applications is also part of the TISPAN vision, immediate standardization efforts focus on a limited subset of applications, leaving room for vendor differentiation by prioritizing support of the broad range of applications, including "over-the-top" applications from Web-based sources. The Cisco IP Next-Generation Network (NGN) vision is fully aligned with TISPAN, and Cisco strongly supports and participates in TISPAN efforts. The Cisco IP NGN architecture and its Service Exchange Framework layer are fully TISPAN compliant, providing optimal support for both emerging IMS-based applications using Session Initiation Protocol (SIP) as well as existing non-IMS IP applications that currently represent the majority of traffic running over service provider infrastructures.
This paper describes the Cisco IP NGN architecture and the Service Exchange Framework's alignment with the current TISPAN standards. Cisco IP NGN value-added features including flexible support for IMS and non-IMS applications and multilayered intelligence are discussed. These features bring significant scalability, deployment versatility, and investment protection to service providers as they deploy and support new services and scale them to support millions of residential and business subscribers.
Overview
Standards organizations developing next-generation network architectures for service providers around the world have agreed on general principles that have been universally accepted. These include the migration of multiple single-purpose network infrastructures to converged networks based on IP and its derivatives. Transport, network services, and applications have been separated into different layers for greater efficiency in the NGN. Network services provide enhanced support for voice, data, and video applications delivered to residential and business users. The network services thereby enable support for a myriad of innovative applications, which are defined as specific uses of services (for example, IP telephony, Cisco TelePresence Service, Web browsing, e-mail, multiplayer gaming, and video conferencing).
This segmentation of transport, services, and applications was agreed upon to better enable service providers to rapidly deploy differentiated new services and to personalize application delivery and thereby reduce customer turnover, enhance competitive differentiation, and provide seamless convergence of fixed and mobile services. Furthermore, a clean architectural separation enables service providers to build out their communications infrastructure with best-of-breed subsystems that communicate via standardized interfaces.
Both the Cisco IP NGN and TISPAN share this philosophy when it comes to a vision of the NGN architecture. However, given the Cisco IP transport incumbency in wireline, wireless, and cable infrastructures, the goal of the Cisco IP NGN is to provide a universal foundation that supports all emerging NGN standards, including ETSI TISPAN, CableLabs® PacketCable™, 3GPP's IMS, as well as International Telecommunications Union (ITU-T) and Alliance for Telecommunications Industry Solutions (ATIS) NGN frameworks.
Common Attributes of Emerging Next-Generation Network Architecture
After different types of traffic converge over an IP NGN, service providers seeking to derive value from end-to-end applications are faced with common challenges. To effectively add further value and insert themselves into transactions between subscribers and applications, service providers must understand the identity of subscribers and the content they are accessing. This means that the common current definition of the network service needs to be revised, since it needs to extend beyond raw - and cheap - bandwidth usage alone going forward in order to provide optimized support for several innovative applications.
Two architectural layers have, therefore, emerged in IP NGNs on top of the IP transport layer, and which, within Cisco's IPNGN architecture, represent the key functions of the Service Exchange Framework: the network service control layer and the session creation and control layer (Figure 1).
• The network service and control layer contains three functional areas that provide standardized, simple, and access-independent ways to establish the identity and location of subscribers, reserve requirement network resources, and help ensure that signaling protocols and media information can be translated in real time by the network to enable effective communications. This layer extends the current control functions within networks beyond bandwidth allocation and control to multiple other responsibilities.
Figure 1. Common Next-Generation Network Layers
• The session creation and control layer is responsible for end-to-end control - linking billable entities to applications and subscriptions - knowing what application is being accessed, and keeping track of session duration as well as other relevant parameters. This session layer is the equivalent of a traditional phone call in the telephony network, but in this new context, handles data, voice, video, and combinations of these types of services. The session layer relies on explicit (using signaling, as with SIP and IMS) or implicit (using technologies such as packet flow optimization) establishment and control of sessions.
TISPAN Architecture
Primary components of the TISPAN architecture include clearly defined subsystems, functional blocks, and defined interfaces. The benefits of fixed/mobile convergence over an IP NGN include a consistent quality user experience regardless of access medium, standardized interfaces for simplified service introduction, and reduced operating costs through a unified network architecture instead of separate networks per service. This next-generation fixed and mobile converged environment provides value-added network services that attract application developers and allow for rapid delivery of new, innovative applications that allow service providers to monetize the next-generation infrastructure.
TISPAN architecture, as shown in Figure 2, defines transport, service, and application layers. Primary subsystems in the transport layer include the network attachment subsystem (NASS) and the resource and admission control subsystem (RACS). These provide identity management and service policy and resource management functions, respectively. TISPAN's layered architecture ensures clear functional compartmentalization, providing for powerful interworking capabilities between different vendors' equipment.
Figure 2. TISPAN Architecture
Challenge
To achieve true service convergence, providers must have intelligent networks that enable them to operate, bill, and manage a number of IMS-based and non-IMS-based services over a range of fixed and wireless access mediums. There are many non-IMS, non-SIP applications that must be supported by service providers today, including peer-to-peer, streaming (for example, video-on-demand [VoD] and IPTV applications), business IP VPN, and messaging (for example, instant messaging, Short Message Service [SMS], and Multimedia Message Service [MMS]). The number of applications continues to grow at a rapid pace. Providers need such applications in their portfolio, not only to meet customer expectations, but also to make use of very substantial revenue opportunities that they create. Consequently, most providers are looking for a means to quickly, efficiently, and profitably deliver both SIP-based and non-SIP-based applications; only this gives them the ability to profit from every emerging revenue opportunity without being limited by technology considerations.
The long-term goal for standards organizations such as TISPAN is to define a standardized method of creating, managing, and monetizing network services and giving the service provider control of not only the applications and services that their networks provide, but also those provided by third-party content sources. The IMS market holds great promise and is projected to rapidly grow over the next few years. Therefore, creating an architecture that supports both IMS and non-IMS applications is key for service providers. Cisco understands the needs of service providers now and the role of the Cisco Service Exchange Framework in the IP NGN architecture is to provide optimized and standards-based support, control, and enablement of IMS-based and non-IMS-based applications.
Solution
As the incumbent across all service provider network infrastructure types - wireline, wireless, and cable - Cisco recognized the value and need to build an IP NGN that could be used by all providers and that supports emerging standards. The result was the Cisco IP NGN.
The network layer of the TISPAN architecture and its primary subsystems are aligned with the Cisco IP NGN architecture, which includes network, service, and application layers (Figure 3). The three core functional elements in the Service Exchange Framework - identity and location management, service policy and resource management, and session and media management - are the equivalent of the generic control block, the RACS, and the NASS in TISPAN. They are the primary functions of the Service Exchange Framework and also support equivalent functional blocks in other NGN specifications such as TISPAN. Cisco provides the most powerful set of transport control and processing functions in the industry by implementing the equivalent of the NASS, RACS, and Border Gateway functionality in the Service Exchange Framework, relying on embedded network intelligence wherever it improves scalability, performance, or cost.
Figure 3. Cisco IP NGN Architecture
Within the service layer, the Service Exchange Framework is tasked with several primary functions that are expanding the very definition of what a network service is and adding value on top of mere bandwidth control. The primary functions within the Service Exchange Framework are common to all NGN architectures, though they have different names.
• The identity and mobility management features reliably establish user identity and location, services that are relevant both to the service provider granting network access and to some content providers, who would prefer a reliable source to provide identification services. The Service Exchange Framework has the ability to pass on verified public identities via a normalized standard interface. This maps into TISPAN NASS.
• The service policy and resource management features provide applications with a simple way to reserve network resources and is the equivalent of the RACS function in TISPAN. Linking quality-of-service (QoS) requirements to flows in a truly mass-scalable and dynamic way has been a longstanding issue. By offering subscribers, and especially applications, simple mechanisms to request and modify network resources, not only are the scalability issues overcome, but, furthermore, network responses are optimally adjusted to the task and to charging strategies. Subscribers paying for content often prefer a reliable delivery method and when given a choice, will often avoid content sources that are afflicted by QoS or scalability problems.
• The session and media management features help ensure end-to-end media and signaling transparency. The networking world will remain a heterogeneous environment with different protocols, media encoding methods, and other boundaries requiring translation and mediation functions for the foreseeable future. Therefore, it is of critical importance that NGN implement embedded mechanisms to convert media formats or signaling protocols in real time to ensure true transparent connectivity. In TISPAN, these functions are part of transport processing, including Media Gateway Functions (MGF), Border Gateway Functions (BGF), and Signaling Gateway Functions (SGF).
Above these core functions are the generic service subsystems. Similar to TISPAN, there is a layer called the common service subsystem that handles universal user profiles and is a common interface from the three main functional feature blocks to the actual service session control subsystems. Network-level sessions are flows associated with billable entities. These flows are linked to application-level sessions in the common service subsystem, allowing for flexible session establishment and control mechanisms. Subsystems defined by other standards - for example, IMS - are supported here. In addition to explicit session control mechanisms provided by IMS, Cisco's packet flow optimization technology supports the implicit ability to create a session-like context from any IP packet flow. This provides for IMS-like control over non-IMS applications wherever it is beneficial for the particular application.
Service Exchange Framework intelligence can be embedded in Cisco's intelligent networking elements using technologies in the network element service control and peering layer whenever it benefits service provider deployment. Significant cost savings, scalability, and performance benefits may result from embedding Service Exchange Framework functionality into network elements. These may include:
• Identity management capabilities simplify authentication using a single sign-on from any access point and build an extensible subscriber profile to enable high-quality, tailored service delivery, as enabled by Cisco Intelligent Services Gateway (ISG).
• Integrated policy management capabilities allow service providers to, for example, dynamically apply a variety of network policies (including QoS, security features, or charging policies) on a per-subscriber basis or per-application basis. By distributing policy management into intelligent network elements, dramatic scalability benefits can result for well understood services that require mass scalability right away. Cisco ISG and the Session Border Controller (SBC) are examples for this unique ability of the Service Exchange Framework.
• Media and signaling conversion are implemented in embedded devices such as the SBC. The SBC provides per-session control and management of IP multimedia traffic based on widely used protocols such as SIP and H.323 for signaling interoperability. This unified SBC implementation eliminates additional appliances and overlay networks, enabling multiservice scalability with easy operation and lower costs. It also builds on Layer 2 and Layer 3 services and provides a flexible and open architecture for a variety of services.
Summary of functions the Cisco Service Exchange Framework is responsible for:
• Applying policies and rules that govern the behavior of services:
– Normalizing identity management and service policy across multiple access technologies
– Enabling identical support and control mechanisms for both IMS and non-IMS services
• Supplying a generic resource, access, and network service control layer that includes:
– Access privileges (authorization to use resources)
– Resource usage (admission control and resource reservation services)
– Quality of service (through administering policies at the data plane)
– Charging and Accounting (providing metering and charging rules for usage-based services)
– Service and application mediation (supporting concurrent services and multiple network elements)
• Horizontal integration with other provider standards, including:
– PacketCable, ETSI TISPAN, 3GPP, 3GPP2, ITU-T, and ATIS
The Service Exchange Framework provides enriched network services to satisfy the needs of the emerging application world. It provides a standardized and straightforward way to reserve network resources for those applications that can benefit and differentiate themselves using that feature. The Service Exchange Framework can offer identity management services to applications and also helps ensure end-to-end signaling and media compatibility. It extends the definition of a network service from a previously commoditized, basic bandwidth service to a richer network service that is at once dynamic, application- or subscriber-controlled, and identity- and resource-aware.
One of the primary benefits of IMS as seen by service providers is that it allows them to gain control over the IP datagrams that can flow in an unpredictable and uncontrollable manner over their infrastructures. IMS explicitly establishes individual sessions using SIP that can be easily attributed to billable entities and provide accurate information related to session origin, destination, duration, and the nature of the session. This resembles the nature of traditional circuit-switched phone calls, allowing full control and personalization irrespective of the access technology being used. The Cisco IP NGN extends the ability of service providers to offer improved application support not only for IMS applications, but also for non-IMS applications.
For non-IMS applications, the Cisco IP NGN has the ability to generate session contexts in an implicit manner by exploiting network intelligence. The Cisco IP NGN Service Exchange Framework can establish applications sessions by inserting itself into network operations during subscriber authentication or by identifying origin, destination, and application content in real time with packet flow optimization technology. This enables the enforcement of policies and the optimization of network resources to meet subscriber service-level agreements (SLAs). Providers can efficiently determine applicable network policies using deep packet inspection at the network edge for both the applications they provide and the applications that subscribers access through Web-based "over-the-top" (peer-to-peer) applications and content providers.
The Service Exchange Framework's functional blocks have a common, open, and extensible interface approach to support client/server and peer-to-peer communications models (Figure 4).
Figure 4. Cisco Service Exchange Framework Support for Standard Application Interfaces
All relevant software interoperability standards and tools are supported, including Common Open Policy Service (COPS), RADIUS DIAMETER, Common Object Request Broker (CORBA), Simple Network Management Protocol (SNMP), and Command Line Interface (CLI). Support is also provided for flexible Web service interfaces involved in service delivery, including Extensible Markup Language (XML), Blocks Extensible Exchange Protocol (BEEP), Simple Object Access Protocol (SOAP), and Web Services Description Language (WSDL). This clean architectural communication model allows the Cisco Service Exchange Framework to optimally interface with any third-parties' service subsystems, offering its superior identification, resource and media management functions to a variety of IMS and non-IMS applications.
The Cisco Service Exchange Framework thus uses network intelligence to bring major advantages to service providers as they converge networks over IP and integrate existing and new applications and services. With technologies that can differentiate between different types of applications, identify individual subscribers, and apply policies, service providers can dramatically enhance the subscriber experience and recruit new, innovative application developers and providers to use their infrastructure. Different traffic and charging policies may be applied to different traffic streams, replacing "best-effort" network response time with priority service for applications with the ability to benefit from this, such as latency-sensitive applications like Cisco TelePresence, video, VoIP, or gaming. Packet filtering, application and subscriber awareness, and policy enforcement can also be used to offer a variety of valuable network-based security services that can turn subscribers into long-term, loyal customers.
The ability to understand how subscribers are using their broadband connections lets service providers establish the relative value of each service being offered and appropriately price services and target marketing efforts. Application awareness can provide the information necessary to create new services and service bundles that are closely aligned to customer needs and that can increase customer loyalty.
With application-aware intelligence integrated into the network layer, providers can dramatically reduce the cost of policy-based network deployment. Personalization can be easily scaled to millions of subscribers as the example in Figure 5 illustrates.
Figure 5. Delegated Architecture: Migration to Quota-Based Broadband Service
Cisco Intelligent Services Gateway (ISG), available in intelligent edge routers, is optimally suited to, in one example, support quota-based services. Embedded policy functions in the ISG can keep track of user quotas and default to basic service allowances after quotas run out. This ability to extremely cost-effectively support new service models is only possible through intelligence residing at the network edge; it is highly scalable and can utilize existing authentication, authorization, and accounting (AAA) servers.
Similarly, some of the new services possible with the application and subscriber awareness provided by the Cisco Service Exchange Framework and technologies that provide packet flow optimization (such as the Cisco Service Control Engine) and apply policies at the network gateway (such as the Cisco ISG) include:
• Self-service:
– Parental controls and content filtering
– Bandwidth on demand
– Pay-as-you-go subscriptions
• Secure broadband services
– Safe harbor and quarantine
– Managed firewall service
– Antivirus, antiworm, and other malware protection
Conclusion
SEF is a key element in Cisco's IP NGN architecture. SEF offers a visionary blend of strict standards compliance with highly differentiated features such as its unique support for IMS and non-IMS applications.
Cisco is an active contributor in emerging NGN standards efforts. To support the immediate requirements of global service provider customers, Cisco has developed the Cisco IP NGN, which complies with all emerging network architecture standards and allows service providers to use their existing infrastructures while being flexible enough to incorporate evolving new services. The Service Exchange Framework enables service providers who are converging their networks over IP cores to more easily and cost-effectively integrate existing and new services - both IMS and non-IMS - in response to and ahead of customer demand. SEF is supported by Cisco's intelligent network elements, which thereby have the unique ability to offer powerful network services - enabling a myriad of exciting new applications for subscribers - and generate new revenue opportunities for service providers.
The unique Cisco expertise in network intelligence lets service providers control their network infrastructures with an unprecedented level of subscriber and application awareness that enables new services and lets service providers exert greater control over all of the traffic traversing their networks. Self-service, new broadband security, mass personalization, and zero-touch provisioning are some of these new services and features possible with Cisco intelligence in the Cisco IP NGN and Service Control Framework - all under a standards-compliant architecture that is fully aligned with TISPAN and other relevant network architecture standards, enabling service providers full and open choice when it comes to picking the best service subsystem solutions for their particular needs.
