VoIP Services:
            PacketCable             Delivers A Comprehensive System
and to leverage relationships with their               Access Network - the HFC network
residential cable subscribers.    ...
                                                                                             Cable Modem
Record Keeping Server                             responsible for maintaining the call state for
resource-constrained segments to manage                  OPERATOR
resource usage and maintain per-flow
reservations carefu...
PACKETCABLE EVENT MESSAGES                           A single event message may contain
PacketCable™ Event Messages Model
                  PacketCable                                Not specified
CONCLUSION                          References
        The PacketCable architecture
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VOIP Services: PacketCable Delivers a Comprehensive System


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VOIP Services: PacketCable Delivers a Comprehensive System

  1. 1. VoIP Services: TM PacketCable Delivers A Comprehensive System NCTA 2002 David McIntosh Maria Stachelek CableLabs Abstract PacketCable architecture. Additional non- voice services are also being analyzed as This paper provides a high-level candidate services for delivery over the overview of the PacketCable IP-based PacketCable architecture. Examples of services delivery architecture as well as a these beyond-voice services include multi- more detailed discussion of the PacketCable player gaming, videoconferencing, and Event Messages framework used to track unified messaging. access network resources used by those services. The PacketCable Event Messages framework supports collection of The cable plant has experienced information necessary to create a PSTN- significant upgrades in the past several style call detail record (CDR) that may be years allowing for the delivery of advanced used for purposes of customer billing, broadband services. The DOCSISTM 1.1 settlements, traffic analysis, and other back specification defines the robust, highly- office functions. reliable, and highly-efficient broadband transport mechanism necessary to support time-critical services such as voice. ARCHITECTURAL OVERVIEW The PacketCable architecture is a One of the fundamental PacketCable multimedia services delivery platform, objectives is to define a QoS-enabled, IP- layered over the DOCSIS 1.1 access based services delivery platform that network, designed to support a wide variety extends the capabilities of the highly of quality-of-service (QoS) enabled IP-based efficient DOCSIS 1.1 access network so as services. The end-to-end architecture as to allow cable operators to deploy a variety designed[1][6], offers a complete system of IP-based services. that includes: device provisioning, signaling, event messaging, configuration The initial service offering identified for management, QoS, and security. These the PacketCable architecture is residential services are managed by specific servers Voice Over IP (VoIP). While the and network endpoints that collectively PacketCable architecture doesn’t preclude create a PacketCable network. the delivery of small-office-home-office (SOHO) and business VoIP services, the Voice over IP (VoIP) is the first focus has been on residential services service identified for delivery over the allowing cable operators to provide value
  2. 2. and to leverage relationships with their Access Network - the HFC network residential cable subscribers. connecting the subscriber to the MSO. The MTA and CM reside on the access network. Several factors differentiate Packet- The CMTS connects the access network to Cable VoIP services from traditional “IP the managed IP network. telephony” services. For example: Managed IP Network - a high ! PacketCable VoIP is a phone-to-phone bandwidth IP network used to connect the service rather than a personal computer- MSOs headend servers. This network is based telephony service. often called the “Managed IP backbone” ! PacketCable services are guaranteed when it is used to interconnect several priority delivery on the DOCSIS access managed IP networks, DOCSIS HFC network ensuring a consistent, high- networks, or connect PSTN gateways to the quality service. PSTN. ! PacketCable services are not delivered over the public Internet. PacketCable PSTN - interconnects with the mandates the use of a managed IP PacketCable Managed IP Network via a backbone that provides service delivery PSTN gateway. consistent with that of the DOCSIS access network. The PacketCable architecture, pictured in Figure 1, provides the comprehensive system necessary to deliver VoIP services. When describing the architecture, we often talk about the three networks involved in the delivery of VoIP services: the access network, the managed IP backbone, and the public switched telephone network (PSTN).
  3. 3. Router Cable Modem Termination System Managed IP Embedded Backbone MTA CMTS Router CMTS Router MTA/ CM MTA/ CM OSS PSTN Call Management Servers Media Servers Gateways Server RKS Media Call Agent Gateway DNS Controller Media DHCP Player Gate Media SNMP Controller Gateway TFTP PSTN Media Player SYSLOG Controller Signaling Gateway KDC Figure 1: PacketCable 1.0 Network Component Reference Model FUNCTIONAL COMPONENTS Cable Modem Termination System As part of the comprehensive end-to- The CMTS is responsible for end system necessary to deliver VoIP managing access network resources for services, the PacketCable architecture PacketCable services. Access network requires several network elements with well- resources are first reserved when service is defined interfaces between those elements. requested, then committed when service is This section describes several key functional delivered, and finally released when the components in the PacketCable architecture. service has completed. Multimedia Terminal Adapter Call Management Server In the home, a standard phone plugs into The CMS manages and maintains the multimedia terminal adapter (MTA) call state for VoIP services. The CMS is allowing voice to be converted into IP composed of a call agent (CA) and a gate packets. An MTA may be designed to be controller (GC). The CA manages the call either a separate standalone device or to be state and controls the MTA. The GC embedded within the cable modem. performs QoS admission control and communicates with the CMTS to allow services to obtain access network resources.
  4. 4. Record Keeping Server responsible for maintaining the call state for calls requiring PSTN interconnection. The RKS is the short-term repository for PacketCable Event Messages. It receives The PacketCable architecture also messages from the CMS, CMTS and MGC supports a hybrid gateway solution that then collates them into coherent sets for takes advantage of legacy PSTN switches designated back office systems for already owned by cable operators while additional applications processing. It serves providing a migration path to the fully IP- as the interface between the PacketCable based PacketCable solution. This hybrid network and relevant back office servers. architecture uses PacketCable IP-based components on the access network and Operational Support Systems circuit switch call control derived from a PSTN local digital switch location. Operational support systems (OSS) contain a variety of supporting servers and infrastructure functions for such activities as ARCHITECTURAL CAPABILITIES provisioning, record keeping for billing, key distribution for security, domain name Several core capabilities are service (DNS) for name resolution, etc. fundamental to the delivery of VoIP services The OSS back office contains service and on the PacketCable architecture. This network management components section provides a high-level discussion of supporting the core business processes. Dynamic QoS and Security. Event Messaging is also a core capability that is Media Server discussed in more detail in a later section. The media server provides network Dynamic QoS announcements and information, e.g. “The number you have called is no longer in An IP-based network, by definition service…” . There are two logical pieces to of the underlying TCP and UDP transport the Media Server, the Media Player mechanisms, delivers packets in a best-effort Controller (MPC) and the Media Player manner. Dropped or delayed packets result (MP). The MPC requests the MP to play in unpredictable end-to-end throughput. announcements based on call state as PacketCable and DOCSIS 1.1 determined by the CMS. The MP is provide a comprehensive, integrated QoS responsible for delivering the appropriate delivery mechanism [4] that ensures announcement to the MTA or to the MG. PacketCable packets are delivered in a guaranteed manner, not a best-effort PSTN Gateway manner. PacketCable splits the management A PacketCable PSTN Gateway can of QoS resources into access network be decomposed into a Media Gateway segments and backbone network segments. Controller (MGC), Media Gateway (MG), This approach allows for different and Signaling Gateway (SG). The MGC bandwidth provisioning and signaling manages the interconnection with the PSTN mechanisms for different network segments: by controlling the MG and SG. The MGC is the origination side, the far end, and the backbone network. Additionally it allows for
  5. 5. resource-constrained segments to manage OPERATOR resource usage and maintain per-flow reservations carefully. The PacketCable OBSERVATIONS DQoS Specification details this design [3]. The multiple vendor and service provider environment into which a cable Security operator enters with the delivery of VoIP services through a distributed architecture PacketCable security spans all requires on-going attention. It has been interfaces in the PacketCable architecture observed that this is not necessarily one-stop [5]. It provides confidentiality for media shopping and each cable operator will be packets and for signaling communication required to develop their own management across the network via authentication, strategies to navigate the variety of vendor, encryption, and key management. It ensures network provider, and service provider that unauthorized message modification, relationships. Take for example, resolving a insertion, deletion and replays anywhere in fault management issue. These can arise the network are easily detectable without within any number of scenarios, each with affecting network operation. Security is their own respective source and solution. interface specific, but the majority of Having the expertise in place, whether in- signaling interfaces are secured using IP house, or supported by a third party, to deal security (IPSec). The media stream is with such an issue will be important. secured by encrypting and authenticating the payload directly. Another example of managing the multi-service provider environment can be In addition to defining the security found in the issue of local number protocol that will be applied to each portability (LNP). In those instances where interface, PacketCable also defines a a PSTN customer would like to keep their corresponding key management mechanism. existing telephone number as part of their There are three basic key management cable VoIP service, LNP comes into play. mechanisms defined for use in PacketCable: The interval of porting a subscriber’s Kerberized Key Management, internet key telephone number has to be managed closely exchange (IKE) with either pre-shared keys in order for the subscriber to experience a or X.509 digital certificates, and randomly seamless service transition. generated keys exchanged within secured signaling messages.
  6. 6. PACKETCABLE EVENT MESSAGES A single event message may contain a complete set of data regarding usage or it The PacketCable architecture may only contain part of the total usage provides a QoS-enabled IP-based service information. When correlated by the RKS, delivery platform for voice and other information contained in multiple event multimedia services. The PacketCable messages provides a complete record of the Event Messages framework provides a service. Event messages are collected and mechanism for tracking access network are sent to one or more back office resources that have been requested and applications such as a billing system, a fraud consumed by these services. This detection system, or a pre-paid services information can be used by back office processor. systems for many purposes including billing, settlements, network usage monitoring, and Originating/Terminating Model - fraud management [2]. PacketCable makes use of an “originating/terminating model” based on The PacketCable Event Messages the PSTN “half-call model.” In this model, framework has been designed to be flexible the originating party’s service provider is and extensible enough to support the initial responsible for tracking information suite of PacketCable voice services, as well sufficient to bill the originating party for as accommodate beyond-voice services in service, and to settle with the terminating the future. provider. The terminating party’s service provider has the same responsibility for the A single PacketCable Event terminating party. This “originating/ Messages framework has been defined to terminating model” supports the various support a variety of service-delivery PacketCable network topologies. scenarios and network topologies. For example, tracking information for services Batch vs. real time - PacketCable that either originate or terminate on the allows Event Messages to be sent to the PSTN, as well as services that stay on the RKS as they are generated. Alternatively, MSOs network are supported by the once generated, Event Messages may be framework. stored on the CMS/CMTS/MGC and sent to the RKS in a single file. Event Message Information Call Detail Records - Using the An Event Message is a data record unique billing correlation ID (BCID) containing information about usage and assigned to a given call, the RKS collects all service activities. Telephone number is an the individual Event Messages for that call, example of the type of information carried and assembles them into a single call detail in an Event Message. An event-based record. The format of the CDR may be format is necessary to accommodate the AMA, BAF, IPDR, or any format distributed architecture where complete appropriate for the billing and other back- “session state” no longer resides in one or office servers that will make use of the two network elements, but is instead spread information. across any of these, i.e. CMS, CMTS, and MGC.
  7. 7. PacketCable™ Event Messages Model PacketCable Not specified Defined in PacketCable •Inter-Carrier Network Element Event CMTS Messages •Batch Billing Systems •Pre-Paid Services Network Element Event RKS CMS Messages •Real-Time Event Billing Systems Messages Network Element •Fraud Detection MGC Figure 2: PacketCable Event Message Model Figure 2 depicts the PacketCable SPECIFICATIONS AND Event Message architecture. By STANDARDS standardizing the transport, syntax, and collection of appropriate Event Message The comprehensive nature of the attributes from a distributed set of PacketCable architecture is the result of network elements (CMS, CMTS, MGC), a suite of Technical Reports and this architecture provides a single Specifications that delineate the end-to- repository (RKS) to interface with end architecture and associated billing, settlement, reconciliation, and interfaces for a complete IP-based other systems. services delivery platform. These Technical Reports and Specifications The CMS, MGC, and CMTS (available at www.PacketCable.com) generate Event Messages for the portion have been accepted as standards by of the communication pertaining to several North American and them. For example, the CMTS generates International standards organizations a “start of QoS” message, when the including the Society of Cable CMTS commits access network Telecommunications Engineers (SCTE), resources to a PacketCable service. American National Standards Institute (ANSI), and the International Telecommunications Union (ITU).
  8. 8. CONCLUSION References The PacketCable architecture [1] “PacketCable 1.0 Architecture described in this paper is a Framework Technical Report”, comprehensive end-to-end system PKT-TR-ARCH-V01-991201, necessary to deliver VoIP and other IP- December 1, 1999, CableLabs, based multimedia services. www.packetcable.com For the delivery of VoIP, the PacketCable architecture can be thought [2] “PacketCable Event Messages of as three networks coordinated through Specification,” PKT-SP-EM-I03- a collection of functional components 011221, December 21, 2001, and servers. The PacketCable CableLabs, www.packetcable.com architecture supports several core [3] “PacketCable Dynamic Quality-of- capabilities, such as dynamic QoS and Service Specification,”PKT-SP- security, that are fundamental to the DQOS-I03-020116, January 16, efficient, reliable deliver of IP-based 2002, CableLabs, services. www.packetcable.com Efforts are underway to develop [4] “Quality-of-Service: A extensions to the PacketCable DOCSIS/PacketCable™ architecture to support a wide range of Perspective”, Venkatesh Sunkad IP-based multimedia services. and Majid Chelehmal, Proceedings of SPIE Volume: 4522, pgs. 87-98, The PacketCable Event July 2001. www.spie.org Messages framework is a flexible and [5] “PacketCable Security extensible model that supports Specification,” PKT-SP-SEC-I05- subscriber billing, settlements, and other 020116 January 16, 2002, back office functions. Going forward, CableLabs, www.packetcable.com the PacketCable Event Messages framework will be expanded to keep [6] “The PacketCable Architecture”, pace with a wide variety of IP-based Ed Miller, Flemming Andreasen, services beyond voice that will be and Glenn Russell, IEEE delivered over the PacketCable service Communications Interactive, June delivery platform. 2001, www.ieee.org 5