Business Considerations of a DOCSIS 1.1 Migration

Transcription

1 White Paper Business Considerations of a DOCSIS 1.1 Migration Introduction With two-way hybrid fiber-coax (HFC) cable networks emerging as viable platforms to deliver cost-effective, high-speed access to the Internet and other IP-based services, cable companies are broadening their service offerings beyond traditional television programming. CableLabs Data Over Cable Service Interface Specifications (DOCSIS) is clearly the standard of compliance and the fundamental approach adopted worldwide to enable IP data, voice, and video services on an HFC network. Using DOCSIS and IP technology, multiple system operators (MSOs) can create integrated, multiservice HFC communications platforms capable of distributing high volumes of data, voice, and video from cable facilities to subscriber homes and offices. Indeed, the triple play of data, voice, and video delivery to the home is the goal of many cable operators worldwide, regardless of size. For more than two years, DOCSIS 1.1 has been the focus of migration plans for the world s cable operators. In 2003, the cable industry will have multiple DOCSIS 1.1-qualified cable modem termination system (CMTS) vendors and multiple DOCSIS 1.1-certified cable modems to choose from. This means cable operators can migrate to DOCSIS 1.1 with confidence that products will interoperate in accordance with CableLabs specifications. What is the motivation to migrate to DOCSIS 1.1? Can a DOCSIS 1.1-enabled system increase a cable operator s return on investment (ROI) above and beyond a DOCSIS 1.0 network? Can it provide access to additional revenue streams, or reduce operational or capital expenditures? This paper discusses DOCSIS standards, outlines benefits to migrate to DOCSIS 1.1, and highlights the challenges of a migration to DOCSIS 1.1. The DOCSIS 1.0 World: Building the Foundation DOCSIS 1.0 was a revolution for the cable industry, providing a standard backbone framework for two-way data transmission over a cable infrastructure. DOCSIS addressed the transmission and operational support infrastructure that cable operators needed, as well as the cable modem equipment required at the home or office to support bidirectional transfer of data across a cable network. DOCSIS defined the radio frequency (RF) and data network technologies required. Before DOCSIS 1.0, multiple vendors had proprietary cable modem systems, which technically worked and met the basic requirements of the industry s early business models for high-speed data (HSD) services. These systems, however, were dependent on unique architectures and did not provide the technical or management capabilities to enable widespread deployment, scaling, and profitability. DOCSIS 1.0 brought interoperability and choice to the market. The costs of CMTSs and cable modems were dramatically reduced, and competition between cable product vendors enabled efficient business models. These business models in turn enabled cable operators to All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 1 of 14

2 compete against other broadband services such as Asymmetric Digital Subscriber Line (ADSL) and traditional telecommunications providers. Today, for example, DOCSIS-based broadband services lead over DSL services in the United States by almost a two-to-one ratio. The primary features of DOCSIS 1.0, which brought about this revolution, were: Interoperable cable modems and CMTSs, which accelerated service deployment and reduced capital and operational costs Common network Management Information Base (MIB) variables A common provisioning model that allowed rapid scaling Industry-wide security standards to address theft-of-service issues Basic quality of service (QoS) techniques Improved systems availability and choice of redundancy options The first generation of DOCSIS DOCSIS 1.0 was designed to capitalize on the most obvious service opportunity for cable operators delivering high-speed Internet access. Emphasis was on standardizing communications between the CMTS and cable modem, as well as reducing the complexity and cost of radio frequency customer premises equipment (CPE) or cable modems. Adoption of the DOCSIS standard assured interoperability of CMTS and cable modem equipment and, for the first time, gave operators the ability to chose between several vendors instead of being locked into one or two. Cable operators can use their DOCSIS HSD network investments and incrementally add equipment to support voice-over-ip (VoIP) or advanced data services. On a DOCSIS 1.0 network, the following types of services are possible: Basic Internet connectivity Tiered data services with QoS per modem Virtual private networks (VPNs) per modem to other cable modems or upstream service providers Basic voice services A DOCSIS-based broadband cable network can support both data and voice traffic. Once deployed, cable operators can take advantage of their standards-based DOCSIS HSD backbone, headend, and hub infrastructure to lower overall deployment and operational costs for new VoIP or commercial service offerings. Cable operators can enable aggressive service price discounting for bundled packages of voice, data, and cable television services to subscribers. By offering data, voice, and video services, cable operators can differentiate themselves from telecommunications providers who typically offer only one type of service and dramatically reduce the churn of customers to Direct Broadcast Satellite (DBS) providers. By taking advantage of the economies of network integration and scalability, cable operators can compete effectively with telephone companies or satellite providers. By properly implementing a multiservice HFC DOCSIS network, cable operators can offer IP cable telephony services at a lower cost compared to the public switched telephone network (PSTN), and can add IP data and television service to the mix. To properly introduce and support VoIP services, cable operators face several challenges. DOCSIS 1.0 lacks the end-to-end network QoS and latency controls needed to support toll-quality voice and network availability specifications. Both of these issues go beyond CMTS or cable modem product qualification and compliance. Implementation of a true multiservice program involves taking a holistic approach to the cable network. To support voice effectively, additional intelligence is needed. Strict QoS and prioritization schemes are needed across the All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 2 of 14

3 network to ensure voice packets reach their ultimate destination within a minimum delay window. Otherwise, jitter can occur, causing distortion or unacceptable pauses during a call. To round out voice services, cable operators must also develop interconnection standards for their IP backbone networks to effectively share packet telephony traffic. Once all of the pieces are in place and the network has been built, cable operators can further expand their service offerings to include commercial services. By addressing this market, cable service providers can take advantage of new high-margin, high-revenue service opportunities. The trend for businesses is to support multiple remote sites, including telecommuter homes and branch offices. Enhancements to DOCSIS 1.0 are needed to support this market. DOCSIS enhancements in the management of public and private encryption keys for CMTS to cable modem communications combined with advanced features such as IP Security (IPSec) for VPNs, firewall, and managed access are needed to support remote access from different venues outside an organization, manage differing service offerings, and ensure security over a DOCSIS-compliant cable plant. The Future with DOCSIS 1.1 DOCSIS 1.1 implemented numerous changes to allow greater flexibility of a cable modem and CMTS to transmit almost any combination of data traffic and real-time traffic such as voice and video. These changes require a fundamental shift in how a cable modem requests service and how traffic is transmitted across the cable network. New features introduced in DOCSIS 1.1 include: Advanced upstream scheduling services that support both enhanced timeslot scheduling mechanisms and jitter-sensitive traffic on a shared, multiple-access upstream link Flow-based QoS with traffic classifications that allow greater flexibility in assigning QoS parameters to different types of traffic Improved security features through baseline privacy interface extensions (BPI+); advanced authentication and security through X.509 digital certificates and Triple Data Encryption Standard (3DES) key encryption are supported Improved bandwidth utilization to respond to changing bandwidth conditions Improved provisioning and authorization Dynamic on-demand QoS features to support dynamic Media Access Control (MAC) messages to create, modify, and delete traffic service flows for on-demand requests A smarter network with better bandwidth efficiency than a DOCSIS 1.0 network; however, DOCSIS 1.1 is not expected to derive financial gains from simply upgrading equipment an increase in ROI from a DOCSIS 1.1-enabled network comes from the value-added services it enables A DOCSIS 1.1 network supports many more value-added services than a DOCSIS 1.0 network. These include: Business services with guaranteed bandwidth service level agreements (SLAs) Multiple PCs connected to multiple upstream Internet service providers (ISPs) from behind the same cable modem Toll-quality VoIP services with committed bandwidth, jitter, and latency tolerances Multimedia video or gaming services with committed QoS Real-time streaming services with improved security and authentication With the additional features in DOCSIS 1.1, cable operators are able to increase revenue by being able to offer services not viable on a DOCSIS 1.0 network. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 3 of 14

4 Services in the DOCSIS 1.1 Environment Data Standard high-speed data services, which made up the core business of DOCSIS 1.0 operations, continue to be supported in 1.1, but with enhancements in the areas of QoS, security, and bandwidth efficiency. DOCSIS 1.0 and 1.1 cable modems interoperate on the same DOCSIS domain. Although DOCSIS 1.1 cable modems have additional features and better performance than DOCSIS 1.0 modems, they can coexist on the same network with DOCSIS 1.0 modems. DOCSIS 1.0 cable modems will not hamper the performance of a DOCSIS 1.1 CMTS; nor will they interfere with operation of DOCSIS 1.1 features. DOCSIS 1.1-capable cable modems support advanced services unattainable on DOCSIS 1.0 devices. Business-grade data services with guarantees of bandwidth and jitter are supported. Multi-occupant dwellings with multiple PCs are able to choose from separate upstream service providers from behind the same cable modem. Data security is enhanced with greater levels of encryption across the DOCSIS network. Superior VPN services are possible, offering a level of security and functioning that allows business users at home to securely access their office networks. Bandwidth management under DOCSIS 1.1 operates in several ways. A standard data user will be supported on shared bandwidth in the same way as DOCSIS 1.0, through a best effort, contention-based algorithm. Customers paying for higher grades of service may be allocated more bandwidth in peak times, compared to lower grades of service. Business customers may have bandwidth committed to their use capacity for which other modems may not contend. Given this committed bandwidth capability, appropriate traffic engineering is a critical design function in DOCSIS 1.1 networks. Operators need to monitor the capacity of their networks, and ensure that adequate bandwidth is available for the dedicated bit-rate services. Voice VoIP services become truly feasible in DOCSIS 1.1 through advanced scheduling schemes like Unsolicited Grant Service (UGS) and Unsolicited Grant Service with Activity Detection (UGS-AD). VoIP over cable is likely to represent a significant business opportunity for cable operators. The technology to offer PSTN or better-quality telephony services over an HFC infrastructure facilitates competition with traditional telecommunications providers. When a voice-enabled cable modem initiates a VoIP call, a UGS service flow is activated through the packet classification process. This UGS would be configured to assign fixed-sized data grants at periodic intervals to and from that cable modem, without the cable modem having to contend or request bandwidth during a voice call. For the duration of the VoIP call, the UGS would be dynamically activated. Upon completion of the call, the UGS would be torn down, and the cable modem would revert back to its contention-based method of requesting bandwidth. Thus, VoIP packets may be delivered over a DOCSIS 1.1 infrastructure with guaranteed bandwidth and jitter characteristics, providing users with superior telephony service. DOCSIS 1.1 VoIP packet prioritization fundamentals, however, do not address end-to-end voice service. The complete definition for VoIP over cable services comes from the CableLabs PacketCable standard. This standard covers such areas as signalling, billing, provisioning, network management, interception, interconnection, and call routing. For a cable operator to produce revenue from voice, DOCSIS 1.1 would be one of the mandatory technical necessities for the transport of packets. The complete array of technical and commercial products and services surrounding the DOCSIS networking infrastructure, however, would also be required. PacketCable-compliant solutions are emerging as the answer to this end-to-end solution requirement. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 4 of 14

5 Multimedia and Video Real-Time Services Multimedia services such as those that use MPEG video formats are supported in DOCSIS 1.1 through another advanced form of bandwidth scheduling. The Real-Time Polling Service (rtps) offers upstream bandwidth from a modem on a periodic basis. The cable modem is polled at regular intervals and asked how much bandwidth is required to deliver the upstream multimedia content. This suits real-time applications where regular transmission of data is required, but variable amounts of data would be sent in each burst. Video conferencing or gaming servers are examples of applications where this form of upstream prioritization is perfectly suited. Another enhanced feature of DOCSIS 1.1 for multimedia services is the improved security mechanisms. BPI+ is an extension of the BPI support in DOCSIS1.0. BPI+ provides cable modem users with data privacy across the cable network. It does this by encrypting traffic flows between the cable modem and CMTS. When BPI+ is enabled, payload traffic in the DOCSIS domain is encrypted, with the CMTS managing an authenticated client/server key management protocol. Cable modems authenticate against the CMTS to gain access to services, which are then encrypted and delivered only to that cable modem. The enhanced multicast support in DOCSIS 1.1, in conjunction with BPI+ authentication mechanisms, decreases the possibilities of theft-of-service attacks of multimedia content, and enables an MSO to authenticate multicast users on a per traffic flow basis, which can be directly tied to billing records. The bandwidth efficiencies of multicasting appropriate multimedia traffic on the network, along with the enhanced security mechanisms built into DOCSIS 1.1, enable charging for multimedia services, thus creating an additional revenue stream for cable operators that was not possible in DOCSIS 1.0. New Features in DOCSIS 1.1 The extended suite of services available in a DOCSIS 1.1 environment can lead to additional revenue from extra value and services being delivered to customers. Service Flows DOCSIS 1.1 introduces the concept of a service flow and a service flow identifier (SFID). A service flow represents either an upstream or a downstream flow of data, which can be uniquely identified by a SFID. Each service flow can be assigned QoS parameters the upstream and downstream class of service (CoS) are decoupled or independent of each other in DOCSIS 1.1. The term SID for service identifier is still used in DOCSIS 1.1 and corresponds to an upstream service flow in a DOCSIS 1.1 environment. Multiple service flows can be assigned per cable modem in either the upstream or downstream direction. Each of these service flows can correspond to a different service class with different characteristics. This is conducive to allowing the cable modem to accommodate multiple kinds of traffic at once, such as standard Internet HSD and VoIP traffic. Dynamic Service Establishment and Advanced Upstream Scheduling Services UGS A service flow is created that allows a cable modem to transmit fixed-size bursts of data at a guaranteed rate and with a guaranteed level of jitter by providing periodic transmission opportunities to the cable modem for fixed-sized frames. This kind of service flow is particularly suitable for VoIP applications. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 5 of 14

6 rtps A service flow is created giving a periodic opportunity for a cable modem to request permission to transmit data by polling one cable modem for a bandwidth request, rather than all modems. This satisfies applications that have a requirement for real-time data transmission, and allows the cable modem to transmit data bursts of varying length. This kind of service flow is particularly suitable for MPEG VoIP. UGS-AD This is a combination of UGS and rtps and is useful for services that require the UGS style of fixed-size and fixed-rate transmission opportunities, but have significant periods where no data is sent. For example, a VoIP phone call where one party is talking more than the other. Why should DOCSIS 1.1 send packets from your cable modem when you are not talking? While words are being spoken and packetized, voice traffic needs to be transmitted, so the cable modem receives UGS-style grants from the CMTS to accommodate this. But when there is silence from the cable modem, the CMTS detects the absence of data and switches to an rtps style mode, temporarily freeing up upstream bandwidth for other users and other services. When the conversation from your cable modem restarts, the CMTS is instructed to recommence the UGS-style grants. In the traffic engineering model, UGS-AD extends the number of supported VoIP-enabled cable modems on the same cable segment. Non-Real-Time Polling Service This kind of service flow is like the rtps; however, polling typically occurs at a much lower rate and may not necessarily be periodic. This applies to applications that have no requirement for a real-time service, but may need an assured high level of bandwidth (a bulk data transfer or a low-demand gaming application, for example). Each of these kinds of service flows may be active for a cable modem simultaneously, ensuring that real-time and non-real-time applications can seamlessly coexist. Classifiers Now that service flows and SFID are created, DOCSIS 1.1 must have a mechanism for cable modems and the CMTS to direct different kinds of IP traffic into different service flows providing different levels of service to different kinds of traffic. Classifiers can be defined based on source or destination MAC address, 802.1Q VLAN ID, 802.1P priority, EtherType, source and destination IP address, IP protocol type, source or destination port number, IP type of service (ToS) bits, or any combination of these. Setting up the specific classification criteria is critical to ensure that traffic is prioritized correctly. Fragmentation and Concatenation In DOCSIS 1.0 environments, cable modems could not split large Ethernet frames into multiple fragments for transmission at different times. This meant that at low upstream channel widths and symbol rates, other cable modems would potentially have to wait for large frames to be transmitted before being able to make their own transmissions. This kind of delay due to serialization of large frames is not acceptable for real-time applications, because it increases jitter and latency. DOCSIS 1.1 allows cable modems to divide large frames of data into smaller parts so that data from real-time services can be interleaved with larger pieces of data from non-real-time services. This helps to ensure that jitter and latency requirements for real-time services can be guaranteed even on channels with a low symbol rates or high congestion. DOCSIS 1.1 concatenates small data packets together and sends them behind the same umbrella of a DOCSIS header, increasing usage of the system and reducing protocol overhead. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 6 of 14

7 Payload Header Suppression Many real-time applications, such as VoIP, may use fixed values in packet header fields over the course of a session or transaction. DOCSIS 1.1 introduces payload header suppression (PHS), which can be used by a transmitting entity to suppress packet header fields with a fixed value. These fields are then restored by the receiving entity, saving bandwidth during the transmission. This feature is typically used with one of the UGS-style services described earlier to decrease the overhead associated with the Ethernet/IP/User Datagram Protocol (UDP) encapsulation of real-time packetized data. BPI+ DOCSIS 1.1 has greatly enhanced BPI support. DOCSIS 1.0 BPI protected user data privacy across the shared cable medium, preventing unauthorized access to DOCSIS-based data transport services across the network. BPI encrypted traffic across the radio frequency interface between the cable modem and CMTS, and included authentication, authorization, and accounting (AAA) features. BPI supported access control lists (ACLs), tunnels, filtering, protection against spoofing, and commands to configure source IP filtering on radio frequency subnets to prevent subscribers from using invalid source IP addresses. The major architectural improvement in BPI+ is the use of X.509 digital certificates and the public key infrastructure (PKI). By using unique digital certificates, which are permanently stored within each cable modem by modem manufacturers, end users are inhibited from falsifying their cable modems identity and stealing or interrupting service. DOCSIS 1.1 BPI+ includes the following enhancements: X.509 digital certificates, providing secure user identification and authentication Key encryption using 168-bit 3DES 1024-bit public key with Pkcs#1 Version 2.0 encryption Support for encrypted multicast broadcasts, so that only authorized service flows receive a particular multicast broadcast Secure software download, allowing a service provider to upgrade a cable modem s software remotely, without the risk of interception, interference, or alteration All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 7 of 14

8 DOCSIS Feature Table Summary Table 1 Summarizes the DOCSIS evolution feature set. DOCSIS Version Services Supported Features and Benefits 1.0 High-speed Internet access Tiered data services and basic VPN functionality Basic voice QoS is based on a CoS that is preprovisioned in the Trivial File Transfer Protocol (TFTP) configuration file for the cable modem. The CoS is a bidirectional QoS profile that has limited control, such as peak rate limits in either direction, and relative priority on the upstream. - DOCSIS 1.0 defines the concept of an SID, which specifies the devices allowed to transmit and provides device identification and CoS. In DOCSIS 1.0, each cable modem is assigned only one SID, creating a one-to-one correspondence between a cable modem and the SID. All traffic originating from, or destined for, a cable modem is mapped to that cable modem s SID. Typically, a DOCSIS 1.0 cable modem has one CoS and treats all traffic the same, which means that data traffic on a cable modem can interfere with the quality of a voice call in progress. The CMTS, however, can prioritize downstream traffic based on IP-precedent ToS bits. For example, voice calls using higher IP precedence bits receive a higher queuing priority (but without a guaranteed bandwidth or rate of service). A DOCSIS 1.0 cable modem could increase voice call quality by permanently reserving bandwidth for voice calls, but then that bandwidth would be wasted whenever a voice call is not in progress. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 8 of 14

9 Table 1 (cont.) Summarizes the DOCSIS evolution feature set. DOCSIS Version Services Supported Features and Benefits 1.1 Toll-quality voice Advanced business services with guaranteed bandwidth Multimedia video or gaming services with committed QoS Real-time streaming services Enhanced QoS to give priority for real-time traffic such as voice and video: - The DOCSIS 1.0 QoS model (a SID associated with a QoS profile) was replaced with a service flow model that supports greater flexibility in assigning QoS parameters to different types of traffic and that better responds to changing bandwidth conditions. - Support for multiple service flows per cable modem, allowing a single cable modem to support a combination of data, voice, and video traffic. - Greater granularity in QoS per cable modem in either direction, using unidirectional service flows. - Dynamic MAC messages to create, modify, and delete traffic service flows to support on-demand traffic requests. - Supported QoS models for the upstream are: - Best-effort Data traffic sent on a non-guaranteed, best-effort basis. - Committed Information Rate (CIR) Guaranteed minimum bandwidth for data traffic. - UGS Constant bit rate (CBR) traffic, such as voice, that is characterized by fixed size packets at fixed intervals. - rtps Real-time service flows, such as video, that produce unicast, variable-size packets at fixed intervals. - USG-AD Combination of UGS and rtps, to accommodate real-time traffic that might have periods of inactivity (such as voice using silence suppression). The service flow uses UGS fixed grants while active, but switches to rtps polling during periods of inactivity to avoid wasting unused bandwidth. - Enhanced time-slot scheduling mechanisms to support guaranteed delay and jitter-sensitive traffic on the shared multiple-access upstream link. - PHS conserves link-layer bandwidth by suppressing unnecessary packet headers on both upstream and downstream traffic flows. - Layer 2 fragmentation on the upstream prevents large data packets from affecting real-time traffic, such as voice and video. Large data packets are fragmented and then transmitted in the time slots that are available between the time slots used for the real-time traffic. - Concatenation allows a cable modem to send multiple MAC frames in the same time slot, as opposed to making an individual grant request for each frame. This avoids wasting upstream bandwidth when sending a number of very small packets, such as TCP acknowledgement packets. - Advanced authentication and security through X.509 digital certificates and 3DES key encryption. - Secure software download allows a service provider to remotely upgrade a cable modem s software, without risk of interception or alteration. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 9 of 14

10 Technical Considerations for DOCSIS 1.1 Environments Designing and provisioning a DOCSIS 1.1 network is considerably more complex than a DOCSIS 1.0 environment. Migrating a network from DOCSIS 1.0 to 1.1 is not as simple as a Cisco IOS Software upgrade. Translating service definitions into technical reality requires planning and traffic engineering. Cable operators will need to plan and spend time designing their DOCSIS 1.1 networks to ensure that technical functioning meets the business model service definitions that fulfill the financial goals of the upgrade. If increased profit is not achieved by upgrading to DOCSIS 1.1, the decision to move forward with the upgrade should be questioned to clearly understand the objectives. Network Design/Traffic Engineering Aligning the business objectives and service definitions of a DOCSIS 1.1 network must be included when developing the plan for the network architecture. Planning a DOCSIS 1.0 network usually included work on RF characterization of an HFC plant, design of a backhaul IP network, IP address allocation, design of a modem provisioning system, writing DOCSIS 1.0-compliant configuration files to match the grades of service specified in the service definitions, creating a network management platform, and maintaining a customer database for provisioning and billing purposes. DOCSIS 1.1 will include all these design functions, plus defining the contents of the DOCSIS configuration files a much more complex procedure. A DOCSIS 1.0 configuration file is written to match a CoS definition from the business model (platinum, gold, silver, bronze, residential, or business). A modem is associated with these classes in the provisioning system. A specific configuration file is downloaded to the modem during registration, and the appliance then complies with that class definition. In DOCSIS 1.0, modems could easily be identified as being part of one class or another. Capacity planning for each DOCSIS domain could be accomplished by spreading appropriate numbers of each class across each DOCSIS domain. For example, a typical DOCSIS domain may contain 5 percent platinum customers, 10 percent gold, 25 percent silver, and the remaining 60 percent bronze. This ensured a spread of each type of customer on each RF carrier/docsis domain. It was possible to ensure that the higher-grade customers had enough priority to request the desired bandwidths during peak times of congestion. With service flows and classifiers in DOCSIS 1.1, a modem will download a configuration file in the same way as in DOCSIS 1.0, but the modem will change its mode of operation on the HFC network depending on the activities being undertaken behind the device. For example, the best-effort scheduling scheme may be used by the modem for default data transfers. During a VoIP call, the UGS-AD scheme could be activated. During a VoD session, the rtps scheme could be activated. Low congestion levels on the DOCSIS domain are not a problem, because there is enough bandwidth to support each of the modems operating in each of the scheduling schemes. As the number of customers increases or the type of services used changes (more voice during peak times of the evening, for example), however, the number of modems sustainable on a single domain will vary as the customer s demand for bandwidth varies. If a majority of customers started using voice services through the UGS-AD scheme, over-provisioning of modems in the DOCSIS domain would cause problems with voice quality. There would not be enough committed bandwidth to support each service. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 10 of 14

11 One of two provisioning methodologies would need to be enabled to support this dynamic style of modem operations. Either undersubscribe each DOCSIS domain to ensure there is ample bandwidth during peak times, or enable a form of load balancing and modem channel changing, so when bandwidth is being fully consumed, the modems requiring committed bandwidth, jitter, or latency are maintained by shuffling modems to different DOCSIS domains where congestion is not present. The upstream channel change (UCC) and downstream channel change (DCC) features supported in DOCSIS 1.1 enable this function. A proactive monitoring system, however, needs to be created to examine bandwidth use on each DOCSIS domain, and move modems between domains to ensure service availability. This would be a complex product to design, which would play a major role in ensuring network stability. An easier method would be to reduce the number of modems operating on each domain, so the peaks of congestion could be absorbed in the same domain. Reducing the number of subscribers is simpler, but it increases cost. There are advantages in DOCSIS 1.1 with regard to radio RF techniques. Intelligent design and monitoring of the network, however, is essential to reap the rewards of these bandwidth-utilization features. DOCSIS 1.1 Configuration File The DOCSIS 1.0 configuration file has less than 50 basic configurable parameters. A DOCSIS 1.1 configuration file has over 130 such parameters. While many areas of the configuration file are similar, the main difference is in QoS. DOCSIS 1.1 introduces the new principles of packet classifications and service flows all controlled through the cable modem configuration file. No additional configuration is essential in a CMTS for classifiers and service flows to be created. The values defined in a DOCSIS 1.1 configuration file are fundamental to the operation of each modem. Detailed design of configuration files is essential to ensure that modems operate in the way specified by the service definitions. There are 19 parameters that define a service flow. As described earlier, a modem can be populated with multiple such flows. Flows do not have to be active all the time. Service flows can be in one of three states provisioned, admitted, or active. A modem can be provisioned with multiple service flows. When required, the cable modem may activate this flow with the CMTS through the use of dynamic service requests. It is important to have correctly defined the service flow. Bandwidth use of the DOCSIS domain is filled with traffic defined by each flow. If a flow is configured incorrectly, the modems using that flow can be using greater bandwidth than defined in the service definition. This may be a problem simply in that services do not match what customers are paying for. This could also upset the balance of modem capacity on a DOCSIS domain, and effect quality of high-grade services such as VoIP and VoD. There are 17 parameters to define packet classifiers in a DOCSIS 1.1 configuration file. In addition to the importance of getting service-flow parameters correct, if packets are misclassified and applied to incorrect service flows, the designed bandwidth travelling through each flow could be vastly different than expected. Multiple classifiers can be associated with one service flow. A one-to-one association of classifier and flow is also configurable. Packets not specifically classified are passed by the primary (default) service flow. The definition of what type of packets to classify, and how to treat these packets with an associated service flow, has to be clearly stated. If too many types of packets are classified and treated uniquely, managing the network could be extremely difficult. Logical classifications linked to revenue-generating service definitions are an advantage and help cable operators. An All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 11 of 14

12 overcomplicated definition of service flows and classifiers simply because it is possible to configure DOCSIS in so many ways can lead to ongoing network management issues which increase operational expense, while not showing substantial benefit to consumers. Provisioning Provisioning a standalone DOCSIS 1.1 network is done exactly the same way as a DOCSIS 1.0 network. A DHCP server manages IP address allocation and populates the cable modem with values to assist in the download of configuration settings to complete registration. If all modems on a network were DOCSIS 1.1, with a mix of service definitions (gold, silver, and bronze, for example), the provisioning system would simply match the incoming DHCP request with a service class, deliver the modem with the relevant configuration file (gold, for example), and the modem would be registered. Complexity grows dramatically when a combination of DOCSIS 1.0 and 1.1 modems are operating on the same DOCSIS domain DOCSIS stipulates that interoperability must be supported between various generations of DOCSIS. This presents some unique challenges for operators. A DOCSIS 1.1 cable modem will register when populated with either a DOCSIS 1.0 or 1.1 configuration file, in either DOCSIS 1.0 or 1.1 mode, respectively. But, a DOCSIS 1.0 cable modem will only register with a DOCSIS 1.0 configuration file. If a DOCSIS 1.1 file is passed to a DOCSIS 1.0 modem, it will never register on the system. For CMTSs, the switch to DOCSIS 1.1 is typically a software upgrade. For cable modems and set-top-boxes (STBs), however, hardware updates may be involved. Modification to the chip set may be needed in the cable modem or STB to support BPI+ and advanced features such as fragmentation. When purchasing DOCSIS 1.0 cable modems, cable operators should confirm whether the CPE device is DOCSIS 1.1-ready and contains the chipset needed to support DOCSIS 1.1 features. Purchasing a DOCSIS 1.1-certified modem is recommended. For backward compatibility, a DOCSIS 1.1 CMTS must support DOCSIS 1.0 and 1.1 modems. DOCSIS 1.1 modems must be able to act as DOCSIS 1.0 modems when connected to a DOCSIS 1.0 CMTS. MAC-Based Client Class Processing Due to the difference in DOCSIS 1.0 and 1.1 configuration files, a means of the provisioning system to match configuration data to cable modem type (1.0 or 1.1) is required. DOCSIS 1.0 cable modems need to be recognized during the DHCP stage of registration and downloaded with a DOCSIS 1.0 configuration file. DOCSIS 1.1-capable modems also need to be recognised during DHCP, and delivered a DOCSIS 1.0 or 1.1 configuration file, depending on the service a customer has paid for. Recognition of the modem type has to occur during the DHCP Discover stage of registration. This is the time when the TFTP server address and DOCSIS configuration file name is given to the modem, which is used later in the registration process to download its configuration. At the DHCP Discover stage, there are only two ways to recognize a DOCSIS 1.0 or 1.1 modem MAC address recognition or DHCP Option 60. The simple way is to match the MAC address of the discovery packet with a known database of MAC addresses. The database would have to have a field identifying the DOCSIS type. Upon cross-checking with this database, the DHCP server could be told what type of modem is making the request, and therefore what type of configuration file should be sent. A management system is essential at the back of a DOCSIS 1.1 network, which knows the MAC addresses of all modems on the network, and what type of modems are present. Packages such as Cisco CNS Network Registrar and Cisco CNS Broadband Provisioning Registrar can perform such operations. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 12 of 14

13 Firmware versions on DOCSIS 1.1-capable modem can pose a problem. If there are DOCSIS 1.1 modems on a network with different versions of firmware some with DOCSIS 1.1-capable code, some with DOCSIS 1.0-capable code the provisioning system would also have to know this information when delivering the DHCP response. It is not impossible to manage this situation, but MSOs will need to be proactive with their modem management processes and ensure they have created a provisioning system that is intelligent enough to know what is occurring on the network. Upgrading a provisioning system from DOCSIS 1.0 to 1.1 could be simple for MSOs with advanced systems today, but it could be a complicated and costly exercise for operators that have had a basic product in the DOCSIS 1.0 environment. DHCP Option 60 One of the other changes in DOCSIS 1.1 specification is the mandatory use of DHCP Option 60 in the cable modem DHCP request. DHCP Option 60 is defined as the Vendor Class Identifier. This field has to be populated by a DOCSIS 1.1-capable modem with the ASCII string docsis 1.1:xxxxxxx. The xxxxxx describes the capabilities of the cable modem. More information can be found in the DOCSIS 1.1 specification, SP-RFIv1.1-I : C The DHCP Option 60 field is the only place an intelligent provisioning system could learn about cable modem properties during the DHCP registration stage, without having prior knowledge of the modem. A DOCSIS 1.0 modem may include the string docsis1.0 in this field, or could leave this blank. A DOCSIS 1.1 must fill in the values. The provisioning system could use this string to trigger the delivery of a DOCSIS 1.1 configuration file and thus not need the accuracy of the MAC database as described above. A combination of MAC address recognition and DHCP Option 60 detection would be a thorough provisioning solution, which would ensure that cable modems receive the configuration file needed to suit the type of modem registering and the service definition that has been allocated. Conclusion DOCSIS 1.1 can enable cable operators to increase revenues and profits, offering valued-added services to consumers not possible in the DOCSIS 1.0 world. These services justify an increased billing model, leading to increased revenue. DOCSIS 1.1, however, is more complex than DOCSIS 1.0. Training, planning, and close network management is essential to ensure the operational expenditures of cable operators do not become more than the increased revenue. Business modeling is the key to success with DOCSIS 1.1 not technology upgrades. The business case has to be solid, and the market requirements have to be quantified and proven. Then, technology upgrades are recommended and can be implemented. DOCSIS 1.1 alone will not increase a cable operator s profit services will. Ongoing work is occurring with the Advanced Physical Layer working group to investigate higher bandwidth for symmetric services and more robust upstream data transmission mechanisms using A-TDMA and S-CDMA technology in part to support more hostile cable plant conditions. This standard known as DOCSIS 2.0 is addressed in a separate white paper. Cable operators thinking of skipping DOCSIS 1.1 and moving directly to DOCSIS 2.0 should reconsider cable operators need to win market share now. DOCSIS 1.1 meets immediate needs for effectively supporting multiple services on a single HFC cable infrastructure. Cable operators with adequate planning can reap the rewards of increased profits today from migrating to DOCSIS 1.1 and expanding their service offering to support voice and advanced IP data offerings. All contents are Copyright All rights reserved. Important Notices and Privacy Statement. Page 13 of 14

14 References 1. Data-Over-Cable Service Interface Specifications. Radio Frequency Interface Specification. SP-RFIv1.1-I Data-Over-Cable Service Interface Specifications. Baseline Privacy Plus Interface Specification. SP-BPI+-I Corporate Headquarters 170 West Tasman Drive San Jose, CA USA Tel: NETS (6387) Fax: European Headquarters Cisco Systems International BV Haarlerbergpark Haarlerbergweg CH Amsterdam The Netherlands www-europe.cisco.com Tel: Fax: Americas Headquarters 170 West Tasman Drive San Jose, CA USA Tel: Fax: Asia Pacific Headquarters Capital Tower 168 Robinson Road #22-01 to #29-01 Singapore Tel: Fax: Cisco Systems has more than 200 offices in the following countries and regions. Addresses, phone numbers, and fax numbers are listed on the Cisco Web site at Argentina Australia Austria Belgium Brazil Bulgaria Canada Chile China PRC Colombia Costa Rica Croatia Czech Republic Denmark Dubai, UAE Finland France Germany Greece Hong Kong SAR Hungary India Indonesia Ireland Israel Italy Japan Korea Luxembourg Malaysia Mexico The Netherlands New Zealand Norway Peru Philippines Poland Portugal Puerto Rico Romania Russia Saudi Arabia Scotland Singapore Slovakia Slovenia South Africa Spain Sweden Switzerland Taiwan Thailand Turkey Ukraine United Kingdom United States Venezuela Vietnam Zimbabwe All contents are Copyright All rights reserved. CCIP, CCSP, the Cisco Arrow logo, the Cisco Powered Network mark, Cisco Unity, Follow Me Browsing, FormShare, and StackWise are trademarks of ; Changing the Way We Work, Live, Play, and Learn, and iquick Study are service marks of ; and Aironet, ASIST, BPX, Catalyst, CCDA, CCDP, CCIE, CCNA, CCNP, Cisco, the Cisco Certified Internetwork Expert logo, Cisco IOS, the Cisco IOS logo, Cisco Press, Cisco Systems, Cisco Systems Capital, the Cisco Systems logo, Empowering the Internet Generation, Enterprise/Solver, EtherChannel, EtherSwitch, Fast Step, GigaStack, Internet Quotient, IOS, IP/TV, iq Expertise, the iq logo, iq Net Readiness Scorecard, LightStream, MGX, MICA, the Networkers logo, Networking Academy, Network Registrar, Packet, PIX, Post-Routing, Pre-Routing, RateMUX, Registrar, ScriptShare, SlideCast, SMARTnet, StrataView Plus, Stratm, SwitchProbe, TeleRouter, The Fastest Way to Increase Your Internet Quotient, TransPath, and VCO are registered trademarks of and/or its affiliates in the U.S. and certain other countries. All other trademarks mentioned in this document or Web site are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (0304R) RDA /03