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Updated:May 20, 2008
High availability for broadband cable IP services is becoming a requirement as multiple system operators (MSOs) enter voice over IP (VoIP) and commercial service markets. Cisco Systems® offers the Cisco uBR 3x10 RF Switch as part of its high-availability cable modem termination system (CMTS) solution set. The Cisco uBR 3x10 RF Switch works with the Cisco uBR10012 Universal Broadband Router to deliver unprecedented levels of availability, scalability, and flexibility when deploying advanced, revenue-generating services such as voice and virtual private networks (VPNs) over cable systems. The Cisco uBR 3x10 RF Switch, combined with the Cisco uBR10012, provides unmatched RF performance, high-availability, and configuration flexibility. The product supports Data Over Cable Service Interface Specifications (DOCSIS), European DOCSIS (Euro-DOCSIS), and PacketCable specifications. Together, the products enable a fully redundant system with no single point of failure.
The Cisco uBR 3x10 RF Switch supports three downstream switch modules and 10 upstream modules. The product provides an Ethernet controller module, an AC or DC power supply, and optional color-coded cabling that is terminated in advance. With connections to the Cisco uBR10012 and the hybrid fiber-coax (HFC) cable plant, the compact three-rack-unit (3-RU) Cisco uBR 3x10 RF Switch supports more than 250 connections and offers a new level of network redundancy suited for high-performance, high-density applications. The product works with Cisco communications-grade CMTSs to create a fully redundant system that enables cable operators to achieve PacketCable system availability, minimize service disruptions, and simplify operations. Each Cisco RF Switch is a multiplexing system that can reroute any of the RF cables connected to active Cisco RF line cards to a spare or backup set of RF line cards.
Figure 1. Cisco uBR 3x10 RF Switch
The Cisco RF Switch provides maximum reliability for the Cisco uBR10012. See Figure 2. The Cisco uBR10012 contains seven active line cards and one standby line card.
Figure 2. N+1 Redundancy on the Cisco uBR10012
The Cisco RF Switch also enables a fully redundant N+1 system configuration for the Cisco uBR10012 Universal Broadband Router. See Figure 3.
Figure 3. Redundancy on the Cisco uBR10012 Universal Broadband Router
With Cisco IOS
® Software, each Cisco RF Switch delivers redundancy by sharing configuration and state information from "working" line cards to "protect" line cards. If a working line card fails, a protect line card assumes traffic responsibilities. The Cisco Hot Standby Connection-to-Connection Protocol (HCCP) maintains all necessary DOCSIS or Euro-DOCSIS state information-including service identifier (SID), service flow, and Media Access Control (MAC) and IP information that enable a standby line card to completely replace an active card when needed. HCCP automatically detects:
• Software or hardware failure, including an external upconverter failure
• Cable wiring failures
• Interface shutdowns
• Line card online insertion and removal (OIR)
• Manual switchover
The Cisco uBR system controls the Cisco RF Switch and external upconverters through Simple Network Management Protocol (SNMP) messages that switch the upstream or downstream frequency on a protect line card as needed. The Cisco RF Switch also offers an SNMP Ethernet interface that allows operators to control the unit without a Cisco uBR10012.
An external RF switch (instead of a line card with internal wiring that would operate as an RF switch) better addresses future scalability. The external Cisco uBR 3x10 RF Switch can be stacked and used for multiple scenarios and different densities. The external design allows cabling migration and line card swap-outs.
High Availability Through N+1 Configuration
The Cisco RF Switch can be installed in a system configuration that enables complete hardware and software redundancy. The advanced high-availability capabilities of the CMTS hardware and software exceed PacketCable specifications for expected downtime and call cutoff. The system hardware is designed to exceed "five nines" (99.999 percent) availability, including both unscheduled and scheduled outages.
Increased Operational Flexibility
Even when high availability is not initially needed to support a service deployment, full hardware redundancy provides the operator with the option to defer a service call until the following business day. Similarly, hardware redundancy reduces ongoing operational costs by eliminating the need for onsite spares. This is especially beneficial in remote areas or in situations where technicians support several installations over a broad geographical area.
• Creates revenue opportunities by enabling voice and commercial services with a fully redundant, highly available DOCSIS or Euro-DOCSIS cable infrastructure
• Lowers operational costs by optimizing Cisco uBR system serviceability
• Protects investments with flexible configuration options when Cisco uBR systems are upgraded or the RF cable plant is reconfigured
• Maintains the efficiency of the RF plant or the DOCSIS or Euro-DOCSIS specification
• Provides maximum reliability by allowing completely passive implementation in the "working path," including latching relays to maintain operation during power disruptions
• Allows complete testability to help ensure that redundant components are functional and that RF performance remains consistent
• Maximizes headend rack space with unmatched port density
Table 1 describes the primary features.
Table 1. Primary Features
Optimal RF performance
• Planar waveguides for optimal signal containment and minimal crosstalk
• Tuned/matched trace lengths for maximum consistency across ports and frequencies
• Printed circuit boards (PCBs) for all traces, for maximum mechanical robustness and durability; leads to maximum RF consistency and manufacturability throughout the life of
• the product
• Gold-plated connections throughout the chassis for maximum reliability
• Microwave-standard MCX connectors, for maximum density while maintaining the stringent RF characteristics demanded by cable operators