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February  2000


The Emerging Role Of The Gatekeeper


The driving force behind the IP revolution is the ability to use packet networks like the Internet for real-time voice and video communications. The International Telecommunications Union�s H.323 specification provides the technical framework for supporting voice and video over IP. The specification defines a �gatekeeper� as an optional network component for call control, managing network resources, and setting policies for how the network can be used (and by whom). As large-scale converged networks are deployed for IP telephony and multimedia conferencing, gatekeepers are transcending their original definition.

Next-generation gatekeepers:

  • Have emerged as the IP network’s “central intelligence agent” and control center for converged voice/video/data networks;
  • Provide a portal for integrating multiple protocols needed for achieving true end-to-end interoperability in a hybrid network that links the existing PSTN with the IP world;
  • Provide the underlying technology needed for implementing “soft-switch” PBX functionality; and
  • Provide the vehicle for delivering compelling new IP services and applications.

All gatekeeper implementations use the same “building blocks,” but IP telephony deployments in enterprise and carrier/ISP environments face different challenges and thus call for different gatekeepers. Indeed “gatekeeper-enabled” capabilities are emerging as competitive differentiators among the product and service offerings of key players in the rapidly growing IP telephony market.

The enterprise market is concerned, first and foremost, with workforce productivity. Hand in hand with this demand for productivity increase is a need to measure sustained hardware and services return on investment (ROI). Upgrading a corporate intranet to support IP-centric, real-time multimedia communications capabilities positions an enterprise to be able to reap the benefits of enhanced productivity as well as increased revenues resulting from more efficient and effective collaboration among workers, with customers, and with supply-chain vendors. Additional benefits of a converged voice/video/data network include cost savings for IP telephony toll-bypass applications, and simplified network management.

Gatekeeper-Enabled Network Management
Enterprise gatekeepers enable IT managers to implement new converged voice/video/data services using existing corporate IP networks without compromising existing mission critical services. Gatekeeper-enabled network management tools provide IT managers powerful, yet easy-to-use controls for defining how voice and video traffic is managed over IP networks — just how much bandwidth may be used for a given call, and what type of calls get priority. Through the gatekeeper, network managers can configure, monitor, and manage the activity of registered network users. They can define who can make calls along with what kinds of calls can be made. Network administrators can also access online event logs to monitor network activity and adjust policies to optimize network performance.

Other unique next-generation gatekeeper capabilities offered by vendors include a database of “neighbor gatekeepers” for optimizing and controlling inter-gatekeeper communications. The database also contains network topology information. This information allows network managers to divide the network into components and use topology island information for efficient subnet routing, enabling least cost routing schemes and load balancing across gateways.

The New Softswitch Enterprise PBX
Next generation enterprise gatekeepers provide their greatest benefit in the form of a compelling “softswitch” alternative to traditional proprietary PBX capabilities such as voice mail, paging, and call waiting. However, gatekeeper-enabled enterprise networks go well beyond simply matching typical PBX capabilities. Converged networks inherently provide a platform for easier implementation of complex services requiring tight integration between voice and data such as “follow-me” call routing and unified messaging. Because gatekeeper logic in new IP-centric “softswitch” architectures is separate from the switching logic of H.323 gateways, the gatekeeper acts as the programming platform to easily implement new services. Ease of service definition and management through the gatekeeper is in turn dependent on the power and depth of API implementations offered by different gatekeeper vendors.

Field service cost savings are also inherently provided through the gatekeeper’s ability to automatically register end points (e.g., phones) as personnel move from one location to another — whether it is across the hall or to a separate geographic location miles away, eliminating “moves, add, and changes” (MAC) service requests.

Whereas the adoption of IP communications in the enterprise is being driven by enhanced productivity and cost savings associated with more efficient network management, increased revenue generation is the business reason for carrier and service provider deployment of IP telephony. To heighten competitive advantage in the increasingly competitive global telecommunications marketplace, service providers are designing converged networks capable of supporting new IP services that in turn will generate new revenue streams. In addition to being the vehicle for implementing next-generation IP services, the gatekeeper is also the component that can “bridge” the existing PSTN with IP networks — a critical need for end-to-end interoperability across a global telecommunications network.
Public expectations for high-quality, low-cost transport, next-generation networks require carrier-class gatekeepers to transport calls in the most cost-effective way to enhance revenues. Meeting these demands requires high performance, scalable, carrier-class gatekeepers.

Service-class networks must be high performance, moving the greatest number of calls — or service requests — in the most efficient and reliable manner. Performance is important in large enterprises but it is critical to the service provider’s core revenue-generation business model. As enterprise-class gatekeepers emerge with access to a host of services that enhance workforce productivity, carriers will use their gatekeeper-driven networks to manage and transport vast amounts of network traffic based on these new IP services. Guaranteed transport will become a primary revenue stream, based on a coupling of least-cost routing mechanisms, high call volume performance, and tie-ins to third-party billing systems. Distributed H.323 and new decomposed gateway architectures using centralized media gateway controllers (such as MGCP architectures) will provide this performance without sacrificing quality of service or compromising service levels.

Gatekeeper-enabled global carrier networks must be able to scale exponentially, well beyond the scope of enterprise-class gatekeepers that are typically equipped with only a limited number of end points (hundreds). Offering any particular service on demand to one or thousands of end points requires rapid “setup and teardown” scalability, only achievable on telecom-grade hardware built to five-nines reliability, coupled with equally reliable, robust gatekeeper software. In carrier environments, one of the primary competitive advantages of deploying gatekeeper-enabled IP telephony networks is the elimination of the need for centralized provisioning entities. Unlike switched networks, clients and servers can be individually added to gatekeeper-enabled converged networks without mandating centralized provisioning.

Besides the obvious need for high performance and scalability, other carrier-class gatekeeper requirements include:

  • Policies: Gatekeeper-enabled architectures provide effective management of underutilized bandwidth through a robust set of predefined or customized policies. These policies provide for tighter bandwidth management, least-cost routing, and detailed call activity logging. Customized policies guarantee fulfillment of service level agreements structured on new criteria such as total number of simultaneous calls in a set bandwidth, or total bandwidth consumption in a specified time increment versus the current “cents per minute” scenario in circuit-switched environments.
  • Systems Interface Support: Connections to LDAP, RADIUS, and DIAMETER for directory services and other critical authorization, authentication, and accounting information needed for call detail records and billing/rebilling.
  • Interoperability: Ties into other telephony protocols including the SS7 signaling protocol used in the PSTN, and new emerging IP telephony protocols such as MGCP for decomposed IP gateways, as well as other communication interfaces for vendor-to-vendor inter-gatekeeper communication for “dial-around” capabilities for accessing multiple service providers.
  • Distributed architecture: Based on a modular, flexible, distributed design — ideal for large service providers seeking to escape more rigid, tiered switching and network architectures that have forced CLECs and other alternative carriers to rely on co-location at competitors’ POPs.
  • Robust API: APIs allow carriers/service providers to integrate gatekeeper operations with customized IP services logic and external databases. The APIs further facilitate formation of a “SUPER gatekeeper” composed of multiple GK components. This feature is critical in design of scalable and reliable networks. Support for third-party “plug-in” modules enables carriers and service providers to quickly introduce new gatekeeper-enabled value-added applications.
  • Network management tools: Tools for rapid and accurate assessment of all call activity and network load are critical for maintaining network performance and efficient call routing based on available network resources.

For carriers and next-generation IP telephony service providers, the gatekeeper provides the essential building block needed for gatekeeper-enabled IP service creation. Gatekeeper-enabled service creation environments are built around carrier-class platforms that provide high performance and fault tolerance. These “open” service creation platforms are key to creating new revenue-generating IP services such as Internet call waiting, calling card services, one-number services, follow-me/find-me services, modem/fax emulation, etc. (Table 1.)These platforms are aimed at speeding service providers’ ability to offer value-added services for converged networks that span across PSTN and IP data networks.

Table 1 First Generation
Second Generation
Third Generation
Customer Service Voice + Web Call Centers Voice + Web + Transaction Call Centers Voice + Video + Transaction Centers
Custom Calling Internet Call Waiting Follow-Me/Find-Me Voice Services Intelligent Appliance Calling Interfaces
User Selectable Service Menu Self-Serve (HTML-based) Multipoint Audio, Data And Video Conferencing Calling Self-Serve Community And Content Services Voice-Activated Services Menu
Unified Messaging Internet Voice Messaging Internet Voice To E-mail,
E-mail To Voice
Fax To Voice
All Earlier Services, Plus Personal Video Messaging Services

It has been just three years since the intellectual property embodied in the ITU H.323 specification became commercially available in the form of the H.323 protocol, and gatekeeper-enabling technology from companies. Since that time, the IP communications revolution has taken hold, and real-time voice and video communication over converged networks is being deployed globally in enterprise and carrier environments. Today, there are hundreds of thousands of people around the world using gatekeeper-enabled IP telephony products and services. As the number of IP-connected devices and people grows and reaches critical mass, IP-centric communications will be commonplace and the gatekeeper will continue to play an increasingly important role as the “heart” of a host of compelling new applications and services for converged networks.

Michelle Blank is Vice President of Global Marketing, RADVision, Ltd. RADVision provides core technology components for building complete H.323 multimedia networking solutions. For more information, visit their Web site at www.radvision.com

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