IP TRANSPORT TECHNOLOGY IN THE CABLE BACKBONE

Gregory K. Hardy Scientific-Atlanta, Inc.

Cable operators who have successfully bandwidth growth outpaces service revenue introduced , voice, and other growth so we need a new model. interactive services to residential subscribers, as well as those penetrating the lucrative Support of Voice, Video, Data Services – business-to-business [B2B] market are The ability to transport analog/digital video, beginning to drive a very different backbone circuit switched voice, and IP data using a traffic pattern, both in volume and wide variety of interfaces over a single composition. We are forecasting a continued integrated network. It is our belief that IP growth in IP data as a percentage of the total based traffic will soon comprise the majority, primary ring traffic. In order to prepare, the and must be specifically planned for. cable operator must shift his attention toward the upgrade of the transport network. Delivery of Next Generation Differentiated Services – The network must support service creation through extensive software Quality of Service [QoS] control, Traffic Evolution and subsequent monitoring and billing of l Assumptions: K Voice traffic is flat these services through Service Level 1800 K Data Traffic doubles (only) 1600 Voice once per year Agreements (SLAs). This is particularly 1400 Data K Revenues increase 20% per important in the B2B market place. Revenues year (optimistic) 1200 K Traffic starts and ends as 1000 800 l Dilemma: Network Resiliency – 99.999% network 600 K How can these revenues uptime, redundant hardware and switched support this network 400 growth?

Percent of Base (CY2000) ring or mesh topologies. 200 K Must find a fundamentally 0 different model! 2000 2001 2002 2003 2004 Simple but Powerful Network Management - In addition to the critical monitoring and fault isolation capabilities, Transport Backbone Requirements the ability to simply “point and click” provision the network is very important. For a cable operator and their CLEC affiliate to be competitively positioned, the Today's Network Architectures transport network must meet certain requirements. In touring any major cable headend facility today, you are likely to see one of the Scalability - Ability to cost effectively following architectures: scale to multiples of tens of Gigabits [Gbps] 1. Multiple networks of transport capacity. As voice, video and 2. Metro DWDM [Dense Wave data services grow the network should Division Multiplexing] expand on a pay as you go basis. 3. SONET multi-service provisioning platforms [MSPPs] Low Cost per Gbps – includes initial costs and operational costs. Remember, Most often found is the system with bit [CBR] services that fit neatly into multiple networks simultaneously operating standard SONET pipes. The bad news is, in the cable backbone, each over a dedicated SONET MSPP’s are less bandwidth efficient fiber. Distances allowing, you may find when transporting variable bit [VBR] IP analog/digital video on a SONET or based traffic and that’s where all of your proprietary digital network, cable modem growth is projected to be. likely over a router network, voice and other data transported on ATM. As service traffic A New Technology grows, a second or third network is often replicated; expect this first in cable modem There is a new aggregation technology services as additional CMTS are required. that will increase transport bandwidth This multiple network approach quickly efficiency and utilization while still offering consumes a majority of available dark fibers the desirable benefits of SONET’s protection and will proliferate facilities with multiple switching and ATM’s QoS. This new transport platforms. technology Resilient Packet Ring [RPR] is currently an IEEE 802.17 working group The introduction and deployment of with expectations to emerge as a worldwide metro DWDM technology allows the cable standard in early 2002. RPR combines the operator to reclaim many fibers for future best of SONET, , and use. Though, two problems still remain. DWDM technologies into a box that Because metro DWDM platforms typically optimizes IP transport in the cable backbone. map a given stream onto its own wavelength, they do not provide a means for efficient Scientific-Atlanta and our technology flexible aggregation of lower rate [usually partner Luminous Networks are active electrical] streams in the DWDM platform. members of IEEE 802.17 and have submitted Secondly, a transport box per service still our version of RPR to the group called remains; each device with it’s own set of Resilient Packet Transport [RPT], for protocols, element management and staffing, inclusion in the final standard. and support requirements for the network. The DWDM solution is still complex and RPT Technology Blocks expensive. RPT technology is centered around four SONET multiplexers are often utilized to major innovations. electrically aggregate low data rate services like 100 BT or OC-3 ATM into higher 1. RPT utilities Gigabit Ethernet over bandwidths, typically OC-48, for transport. Fiber, a packet-switched optical transport Current technologies recently released are layer, optimized for efficient IP transport. based on new mappings of circuit-switched This transport layer is similar to an Nx payloads into SONET frames. These Gigabit Ethernet physical layer, with the products, often referred to as SONET addition of robust service mechanisms like MSPP’s [multi-service provisioning performance monitoring, network platforms], map traffic into different size synchronization, and control packets. RPT circuit pipes based on multiples of SONET achieves SONET–level robustness at Gigabit STS-1. Also available are numerous ATM Ethernet costs. and VP networks based on ATM over SONET technology. Good news is, this RPT's physical layer can be single aggregation approach to transport simplifies wavelength or DWDM and is decoupled the cable backbone, particularly in constant from the logical topology of the network. This enables the cable operator to configure point-to-point, rings, and mesh networks. Service & QoS

RPT (add) 2. RPT enables full system redundancy Ingress Packet Policy & Traffic Class Based and 50 ms span restoration switching. RPT Classification Metering Shaping Scheduling also allows up to 200% of the ring bandwidth Traffic [work and protection] to be over provisioned Shaping RPT (pass) Class Based with traffic when there is no span break. Scheduling Typically, SONET requires the protection ring to be in reserve for protection switching Class Based Policy & Traffic Class Based Scheduling Metering Shaping Scheduling events. Egress RPT (drop)

3. All traffic is statistically multiplexed in Layer 2 packets at point of ingress. This Implementation Benefits of RPT provides optimum efficiency in the transport of bursty IP traffic that otherwise would be In implementation, RPT will allow the limited by preconfigured SONET pipes. cable operator to effectively deploy new RPT yields a 30 to 50 percent increase in services, simplify network design, and effective transport capacity over comparable reduce operation expenditures. circuit switched networks operating with similar nominal bandwidth links. RPT eliminates adaptation to connection-

oriented protocols [like SONET and ATM] and recovers some lost overhead. These BW Efficiency of SONET layers are replaced by a thinner and more DS-3 45 100 100 Base T 100 51 OC-n 155 155 100 Base T flexible RPT and MPLS stack capable of SONET Hub 1 DS-1 transporting IP services, TDM voice circuits, 1.5 Ring SONET BW Service BW Hub 2 51 Hub STS-1 and video. 1411 x 51 = 145 24516 101.5 3 2 11.5 41 1004.5

Headend Hub OC-12 2 x 622 = 421244 Hub 3 1.5 51 TOTAL: 1805 1262.5 DS-1 Hub 4 10 10 Base T 51 4.5 Eliminates Adaptation Layers GbE 51 3 x DS-1 1000 1244 <70% Efficient and Overhead

4. RPT provides extensive QoS support, IP TDM including policing, shaping, class-based services services IP TDM ATM queuing, and flexible scheduling employing services services MPLS strict priorities and algorithms. RPT also SONET Resilient Packet Transport supports minimum latency express paths for Rigid Optical Layer Configurable Optical Layer packets passing thru [but not dropping] at a hub. RPT overcomes the best effort IP QoS The RPT packet includes a 6 bytes RPT limitation found in Gigabit Ethernet to offer header and 4 bytes MPLS and contains all a strong alternative to ATM. the necessary information to move the packet

through the network. This is a very small tax relative to SONET and ATM for similar functionality. next router. Today's solution requires the cable operator to upgrade to a higher capacity RPT Protocol Overview router.

CRC Payload Label R-header

The Layer 3 Bottleneck

Error detection Ethernet Port ID DA/SA => Drop or Pass MPLS Service type Pass – Class of Service IP Time-to-Live Choke Point! Router TDM, FC, MPEG Payload Type Router Router Core

Router Router Router

Router

Host Host Host Central to RPT is the ability to enable Host Host Host switching and transport at the packet level. Packet level processing yields infinite granularity and maximizes transport RPT eliminates the layer three bottleneck and bandwidth efficiency. Eliminating the need expense by operating in Layer 2-1/2 and to map bandwidth into preconfigured circuits using the RPT header for pack destination that are always the wrong size. RPT enables information. As each packet traverses the provisioning of more services to more network, the RPT header determines if the customers over the same cable backbone packet should be dropped or passed. RPT network. Transport bandwidth may be enabled boxes will likely reduce network provisioned in exacting amounts with dependence on high capacity routers. flexible burst capability. RPT should better position the cable RPT technology transports video, data, operator or its CLEC partner to sell and voice payloads using MPLS [multi- differentiated services to end users [often protocol label switching] techniques. The B2B customers] through Service Level video payload consists of MPEG data Agreements [SLAs]. A SLA is a contract originating from either a QAM IF or DVB- between the operator and the user/subscriber ASI interface. The data payload is IP and setting expectations and pricing for transport originates from 10/100 BT, 100 BFX, GigE, services while establishing penalties for non- or OC-n POS interfaces. The voice payload compliance. These end-to-end service consists of T-1 or E-1 frames. RPT supports guarantees include latency, bandwidth, and TDM voice by establishing network packet loss. For a successful business, SLAs synchronization to an external Stratum clock require all traffic to be trackable, verifiable, (BITS, T-1). This allows transport of toll and billable. quality voice services originating from TDM equipment. RPT enables this high-end service capability through the implementation of In conventional router networks, QoS and network management. Key to bottlenecks can occur when L-3 packet RPT's implementation of QoS is the traffic exceeds the capacity of the router to preclassification of each [voice, video, data] efficiently "open" each packet, read the packet as it ingresses the ring. Classification destination address, etc., and forward to the is based on "diffserve" code, source/ destination address, port, MPLS tag, or deliver, monitor, verify, and bill for application or a combination of the above. differentiated IP services. RPT offers eight QoS classes from express forwarding [EF] for time sensitive services Summary like video or toll voice, ranging to best effort [BE]. Once a preclassified packet enters the It is forecasted the growth and pattern of ring, software algorithms manage traffic traffic in the cable operator's backbone congestion and properly balance network will migrate towards IP data. add/drop/pass traffic at each node. However, the MSO must also reliably and efficiently transport analog/digital video, and RPT's Network Management Control is TDM voice services over this same network. standards compliant and includes the ability RPT technology offers a packet level to control the provisioning of guaranteed alternative that is efficient for all types of services and implement SLA's. Point and transport traffic, and allows the true click provisioning for bandwidth economic benefits of a single platform management, cross-connects, class of transport solution to be realized. service, and accounting management facilitate the cable operators ability to