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Feature Article
August 2002

PacketCable And The Road To Cable Telephony


CableLabs� PacketCable project began in late 1997, and in December of 1999 released the first set of technical specifications for an IP-based services delivery platform capable of providing residential telephony service. PacketCable services require the managed Quality of Service (QoS) and other advanced capabilities provided by the DOCSIS 1.1 Cable Modem specifications. CableLabs members were eager to have industry specifications that allowed vendors to build products that meet the needs of the cable industry and assurance of multi-vendor systems that interoperate.

The PacketCable specifications were released in phases. The initial phase, PacketCable 1.0, is the foundation of the IP-services delivery platform and provides sufficient functionality necessary for an MSO to deliver residential telephony service. PacketCable 1.1 adds additional functionality necessary to provide a primary line telephony service, and PacketCable 1.2 defines how to connect multiple PacketCable networks.

One goal of PacketCable 1.0 was to provide sufficient detail to allow vendor interoperability and capabilities as needed for simple telephone calls within a single cable operator (MSO) network. The 1.0 release included specifications covering:

  • The required and recommended codecs;
  • Dynamic quality of service control on the cable plant;
  • Signaling based on MGCP (NCS) for use between the softswitch (call management server, CMS, in PacketCable parlance) and the residential gateway (multimedia terminal adapter, MTA);
  • Signaling based on MGCP (TGCP) for use between the softswitch (media gateway controller, MGC, in PacketCable parlance) and the PSTN media gateway (MG);
  • A specification of event messages used by a record keeping server (RKS) to correlate events to create billing records;
  • A protocol for transporting SS7 ISUP and TCAP messages between signaling gateways and softswitches;
  • MIBs and MIB framework documents for the MTAs;
  • Provisioning protocols and techniques for the MTAs; and
  • A security specification addressing the PacketCable defined interfaces.

In addition to these PacketCable 1.0 specifications a number of 1.0 related technical reports have been published. These include:

  • The PacketCable Architecture;
  • Call flows for various scenarios including both cable network devices and PSTN devices; and
  • An overview of the operation support systems (OSS) for cable telephony networks.

Between December 1999 and November 2000 the PacketCable project released the PacketCable 1.1 specifications. The goal of the 1.1 specifications was to add the necessary components to enable primary line support in the cable network. PacketCable 1.1 was still targeted at a single MSO implementation. The additional specifications issued included:

  • Primary line support requirements;
  • Management event reporting and control mechanisms;
  • CALEA requirements and processes for communications service providers (known in PacketCable as the Electronic Surveillance Protocol Specification, ESP); and
  • An MGCP package for the control of media servers (audio players).

In addition to the PacketCable 1.1 specifications, four new technical reports were generated:

  • The line control signaling system architecture;
  • More management event clarification (the identifiers);
  • A VoIP availability and reliability model; and
  • Call flows to go along with the ESP specification.

PacketCable 1.2 addresses how telephony networks operated by different MSOs can work together to provide end-to-end services. The specifications include a SIP-based signaling specification (CMSS) for inter-CMS operation, and an interdomain quality-of-service specification. An architecture technical report was also issued that included the interdomain aspects of PacketCable 1.2.

The specifications for all three releases continue to be updated and reissued as necessary to reflect clarifications and corrections based on experience gained from vendor product implementation and multi-vendor interoperability testing.

CableLabs has been engaged in PacketCable interoperability testing for the last three years. In line with the testing strategy used for DOCSIS, PacketCable has built a certification program. Customer-premise equipment (MTA) is �certified� against requirements in the specifications, while network elements that are under the care of operators are �qualified� against the specifications.

PacketCable has been operating a test network with those products that contain the most advanced PacketCable features. This Advanced Interoperability Test Network (AITN) gives the industry a fully operational PacketCable network model using PacketCable protocols. The AITN demonstrates that the architecture works and provides an operational forum for interpreting the specifications and evaluating interoperability. In order to ensure the AITN contains products with the most advanced PacketCable features, product acceptance into the AITN is based on the results of PacketCable interoperability test events in accordance with criteria established by CableLabs. The AITN is reviewed and modified as appropriate to ensure that the most advanced products with the most advanced PacketCable capabilities are available for interoperability testing.

In addition to the continued work on the telephony specifications, CableLabs has also chartered a new group to look at multimedia applications over the broadband cable. The new DOCSIS 2.0 specification was released at the end of 2001. DOCSIS 2.0 increases the data rate on the cable upstream plant to significantly greater rates.

Cable companies have been trialing VoIP solutions for at least five years. A lot has been learned, and there is more yet to learn. Nearly every one of the larger MSOs has trials in progress: Lab trials, field trials, or both. The early trials predated and led to the PacketCable work; most of the trials now in progress reflect the latest PacketCable architecture and specifications.

Indications are that the first revenue trials based on PacketCable specifications will begin later this year. There are still some issues to be resolved. The work continues as the specifications are subjected to more vendor implementations and more scrutiny from network operators, but the present work provides an adequate basis for initial deployments.

There are a number of factors that jointly impact the deployment rate. Among these factors are:

The need to upgrade or rebuild plant: To deploy DOCSIS-based PacketCable solutions requires high-quality two-way plant. Customers are demanding cable modem services, and most MSOs are moving as quickly as economics allow to rebuild their plants to support high-speed data services; the same rebuild will support the two-way voice services and the multimedia service interfaces now being standardized. The rebuild is nearing completion in most of the larger MSO networks and has been completed in many of the smaller ones. A few networks still have not completed the necessary upgrades.

The need for trained technicians: The Society of Cable Telecommunication Engineers (SCTE) now provides technician certification in the area of cable telephony; many of the younger engineers coming into the MSOs today are Cisco-certified network engineers or have received similar training as part of their education. The workforce is available and rapidly evolving to meet the needs of the MSO operated next-generation multiservice, multimedia network.

Capital available for new network equipment: The economic impact of the 2001 and early 2002 market retraction has limited the amount of capital available to the MSOs for new equipment purchases. As the recovery occurs through the end of 2002 and into 2003 the rate of deployment should pick up.

Final availability of PacketCable compliant product: Since the PacketCable specifications are only recently stable, the number of vendors that have mature product in each area of the network is less than some of the MSOs are comfortable with. The vendors are rolling out product as rapidly as the current economics allow, and the number of available products is growing each month.

The broadband access network is a reality. The specifications are in place, and vendors are delivering products today that comply with these specifications. Deployments are beginning to occur, and the rate of deployment will increase as the network operators get more comfortable with the equipment and the CapEx budgets recover.

I wish to express my sincere appreciation to the staff at the CableLabs PacketCable project who reviewed this article and made excellent suggestions. Their suggestions have, I believe, ensured that the article portrays an accurate picture of the process and progress of the PacketCable project. 
-- Don Stanwyck

Don Stanwyck is VP, Technology and Standards at IP Unity. IP Unity is an emerging technology leader offering a carrier grade services platform for enhanced voice and telephony applications over ATM, TDM, and VoIP networks. The company�s offerings include media servers, applications servers, and prepackaged enhanced services. For more information visit their Web site at www.ip-unity.com.

[ Return To The August 2002 Table Of Contents ]

Five Suggestions for MSOs Considering Packet Voice


The same old 80-20 rule � where 20 percent of the customers provide 80 percent of the profits � can also be applied to the residential sector of the telecommunications industry. Not surprisingly, virtually every provider these days is laser focused on meeting the needs of that top 20 percent. Fortunately for cable television (CATV) providers, strong penetration into the homes of this top tier has already been achieved through basic and/or advanced cable services, and in some cases video-on-demand or high-speed modem services.

Industry figures show that the capability to offer additional voice services � creating the so-called �Triple Play� � has the potential to provide substantial financial returns. According to Cahners-Instat Group, total worldwide cable telephony subscribers are forecasted to rise from 2.8 million at the end of 2000 to over 15 million by 2005, with the vast majority of subscribers residing in North America and Western Europe. The high-tech market research firm also believes resulting worldwide cable telephony revenues will rise from $1 billion in 2000 to over $6.5 billion in 2005. While MSOs can boost revenues and profitability by providing a �one stop shop� solution, consumers also benefit from new attractive services and pricing discounts by obtaining multiple services from a single provider, with the added convenience of consolidated billing.

To offer new services and better economics requires the MSO to deploy Voice over Packet access solutions and leverage softswitches in greenfield build-outs, or legacy switches in existing build-outs. With Voice over Packet (VoP), MSOs also have the potential to increase profitability due to its relatively low cost compared to a circuit switched voice solution. In addition to the reduced capital expenditure of VoP, operational costs will also be considerably lower � a number of industry studies show potential cost savings of between 40 percent and 60 percent compared to circuit switched voice solutions. Adding a separate circuit switched network for voice to an existing cable network requires a major financial commitment due to the amount of additional network costs plus service, support, and staff required. In addition to leveraging much of the MSO�s existing network, a VoP solution can also leverage a higher degree of automation and offer many new off-the-shelf applications. In some instances, the customer can make changes to their service and plans without call center involvement, and new services � such as unified messaging and conferencing services � can be added from the MSO�s Web site, for example.

Assuming an MSO has decided to enter the world of packet voice, in most cases they will need assistance in building and deploying a VoP network. Here are some key points to take into consideration along the way:

Experience Counts � Designing, testing, and implementing a VoP solution is not an easy proposition. A recommended course of action for MSOs is to partner with either an experienced Network Equipment Provider (NEP) or Systems Integrator (SI).

Insist on a Complete Solution � The core components needed to deliver VoP service typically include a Media Terminal Adapter (MTA), a Cable Modem Termination System (CMTS), a media gateway, and either a CLASS 5 switch or a softswitch. MSOs should insist on a complete solution from their NEP or SI to avoid the additional cost and hassles that almost always occur with partial solutions.

Look for Best-of-Breed Vendor Partners � Currently, no NEP manufactures all of the components needed to deliver VoP service. As such, MSOs should ensure that their chosen NEP or SI partners with best-in-class vendors that have field proven VoP experience and the financial ability to survive the current industry downturn. Even though an MSO will rely on one NEP or SI, they can still obtain a best-in-class solution for current and future needs.

One Size Does Not Fit All: Insist on Scalability � MSOs should build, grow, and manage their voice subscriber business at pace with market demand. In addition, subscriber size and penetration will vary by different markets, thus MSOs must insist that NEPs and SIs offer solutions that are cost optimized for these different opportunities. For example, MSOs should select NEPs that have media gateway partners that offer several options of cost optimized platforms.

Focus on Investment Protection � Investment protection is key for today�s MSO, which is one reason why VoP makes a great deal of sense. MSOs also must be sure that the solution they receive from their NEP or SI � and each component of it � has a clear evolution strategy to accommodate change and the ability to leverage new technologies as they emerge.

Now that CATV has achieved high penetration rates, MSOs of cable broadband networks should be looking toward offering �triple play� data, voice, and video bundled services to ensure ongoing profitability from high-value customers. With solutions available today that address multiple network architecture options and a little forethought, MSOs can meet their migration, cost, timing, and risk concerns in deploying packet cable telephony.

Ben Rabinowitz is vice president at AudioCodes, Ltd. AudioCodes is at the forefront of voice and data convergence. The company designs, develops, and markets Voice over Packet media gateway technologies and systems for converged networks. For more information visit the company online at www.audiocodes.com.

comMATCH Delivers IP Telephony For German MSO

The idea of offering competitive IP telephony services over cable TV to end-users has captivated Multi-Systems Operators (MSOs) for years. Although cable operators all over the world are upgrading their Hybrid Fiber Coaxial (HFC) infrastructure to enable bi-directional wideband services by using the standard IP DOCSIS protocol, significant technical and operational barriers have discouraged the majority from commercially offering fast Internet connections and IP telephony using a cable modem in the home premises.

To make the vision a reality, cable operators must overcome a number of hurdles, the first being the need to provide cable TV end users with a reliable high-quality service with the same level of features home users are accustomed to receiving from their legacy telephony provider (ILEC). MSOs are also required to offer a telephony network that is both durable and expandable, ensuring a simple migration to future network architectures. MSOs also face national regulatory mandatory requirements such as enabling Legal Call Interception (CALEA) by various law enforcement authorities, when and where required. Other requirements include call metering � call charging (e.g., ISDN AOC), support for national telephony protocol variants, and more.

One company that has succeeded in meeting these challenges is SDTelekom; a German municipal cable TV operator that currently serves over 162,000 inhabitants in Schwedt, Germany. Using IBM Global Services as the main integrator, SDTelekom provides its residential and business end-users with Fast Internet and IP telephony services. IBM provides the solution in collaboration with comMATCH, a next-generation VoIP gateway provider.

The SDTelekom solution is based on comMATCH�s Duet 6002 VoIP carrier-grade access gateway. Using this product, MSOs can offer their customers cable TV, videos, high-speed Internet access, and at the same time deliver real telephony service, without the huge expense of installing new distribution networks or investing in new dedicated hardware in the headends or at the customer premises. The Duet interconnects legacy Class 5 Local Exchange with the cable TV IP DOCSIS network, which is implemented by using Cisco Systems� cable headend products. The resultant solution enables SDTelekom to provide reliable high-speed data, fax, and feature-rich telephony services, including support of three-way call, call forward, call waiting, caller ID, and free phone (1-800), as well as other popular services.

The benefits to SDTelekom are numerous. The solution enables the company to deliver reliable, high-quality, feature-rich telephony services, with minimal risk, since the Class 5 switch generates all of the required services, in much the same manner as they are provisioned today by the ILECs. Moreover, SDTelekom can use Siemens� Class 5 EWSD switch for billing and administration. The solution combines cable TV infrastructure with the following standard components: eMTA, CMTS/INA, and the mature Class 5 switch. In addition, Siemens� switch views SDTelekom�s subscribers through comMATCH�s Duet gateway as regular telephony subscribers, thus enabling more than 3,000 legacy PSTN services. Last but not least, this end-to-end solution supports all the requirements of Euro PacketCable Capability Set 1 (CS1), and most of the services of Capability Set 2 (CS2) available on the market today.

comMATCH delivers Carrier-grade VoIP gateways that enable feature-rich telephony over IP and TDM networks. The company�s products are designed to enable customers to seamlessly bridge legacy PSTN and next-generation IP networks. For more information, please visit www.commatch.com.

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