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Preparing Cable for Telephone Reliability David Waks System Dynamics Inc. Spring 2000 Voice On the Net Wednesday, March 29, 2000 Copyright © 2000 System.

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Presentation on theme: "Preparing Cable for Telephone Reliability David Waks System Dynamics Inc. Spring 2000 Voice On the Net Wednesday, March 29, 2000 Copyright © 2000 System."— Presentation transcript:

1 Preparing Cable for Telephone Reliability David Waks System Dynamics Inc. Spring 2000 Voice On the Net Wednesday, March 29, 2000 Copyright © 2000 System Dynamics Inc.

2 Copyright © 2000 System Dynamics Inc. Slide 2 Summary Modern hybrid fiber-coax (HFC) cable plant is much improved, but has multiple potential points of failure Data network and physical cable plant are distinct network management domains Present cable telephony solutions incorporate plant management systems IP telephony over cable will require high availability to be competitive with ILEC Several approaches to achieve high availability SNMP-based CPE such as cable modems will provide the capability to monitor the physical cable plant Several vendors are developing solutions based on SNMP

3 Copyright © 2000 System Dynamics Inc. Slide 3 Plant Requirements for Primary Telephony Availability - both MTBF and MTTR –Needs to match customer experience and expectations: always get dial tone Cable plant is underpinning for all services –Amplifiers in cascade, node size –Powering - centralized at node versus distributed –Many possible points of failure Different operational models –Twisted pair telephone plant is not monitored single failure usually impacts only one subscriber line –Cable plant has generally not been monitored single failure can impact many subscriber lines Three approaches to achieve high availability –Redundancy - fiber, electronics –Eliminate points of failure –Proactive network management of physical cable plant

4 Copyright © 2000 System Dynamics Inc. Slide 4 Source: General Instrument Typically amplifiers in cascade Traditional Cable Architecture - Coax Tree-and-Branch Headend (or hub site) Amplifier

5 Copyright © 2000 System Dynamics Inc. Slide 5 Modern Hybrid Fiber-Coax (HFC) Architecture Source: General Instrument Neighborhood Fiber Coax Node or optical-electrical interface Replaces trunk cascade with fiber to node in each neighborhood 125 to 2000 home fiber serving area Broadcast star-bus Star from headend to node Bus from node to homes Many fewer amplifiers AT&T testing fiber passive coax approach Logical extension of HFC 50 to 75 homes per mini node Reduces or eliminates trunk amplifiers Headend (or hub site)

6 Copyright © 2000 System Dynamics Inc. Slide 6 Circuit-switched Cable Telephony Current HFC telephony products incorporate plant management systems –NIU acts as status monitoring transponder –Centralized analysis and reporting systems –Detect failures and help isolate to specific home or small segment of cable plant Hub Site or Headend HFC distribution plant Customer Home Voice port ( or NIU) Host digital terminal Arris Interactive Cornerstone equipment Class 5 Switch PSTN GR-303 or V5.2 (T-1/E-1)

7 Copyright © 2000 System Dynamics Inc. Slide 7 Traditional Status Monitoring Systems Can monitor many possible points of failure –Optical nodes –Power supplies –Amplifiers (rarely) Best implementation - Rogers Cable (largest in Canada) –Transponders on all nodes, power supplies and amplifiers –Data collection system at each headend –Identifies trouble spots using weekly figure of merit for each secondary hub (~5,000 passings) –Isolates problem to specific amplifier using fault-detection analysis of transponder data trends –Substantial measurable improvement in data throughput –Moved from R&D to system-wide implementation Most operators have not invested in status monitoring –Monitor nodes and power supplies, not amplifiers –Dont want proprietary protocols, equipment and software –Believe solution based on industry-standard protocols and software would be much less expensive

8 Copyright © 2000 System Dynamics Inc. Slide 8 New Digital CPE Offers Better Solution DOCSIS cable modems now industry standard –Many certified vendors for modems and headend CMTS –Rapidly replacing proprietary technologies –Moving to retail distribution, customer installation All new digital cable devices support SNMP –DOCSIS modems include robust SNMP MIB structure –Digital set-top boxes –IP telephony CPE based on PacketCable specs Digital devices will provide many more test points than traditional status monitoring –Many cable systems already have higher penetration of customer-provided SNMP devices than possible with traditional amplifier-mounted transponders –Provides closer determination of failure location

9 Copyright © 2000 System Dynamics Inc. Slide 9 Need New Software Systems DOCSIS modems provide two types of data –Traditional measurement of signal levels –Error counters on PHY layer of protocols Needs software to realize potential –Map CPE measurements against model of plant topology –Isolate problems to small section of plant –Distinguish between in-home and plant problems –Anticipate failures No off-the-shelf solutions yet, but several vendors working toward one –Cisco –Com21 –Cheetah Technologies –C-COR.net

10 Copyright © 2000 System Dynamics Inc. Slide 10 Cable Operators Taking Several Approaches Rogers –Substantial investment in status monitoring Cox –Redundant fiber - ring in ring architecture AT&T BIS –Reduce or eliminate points of failure with fiber passive coax extension of HFC Operators will mix-and-match to achieve desired reliability at reasonable cost CPE-based status monitoring highly promising –Based on existing CPE and centralized software –Much lower cost than rebuilding plant –Fastest to deploy once proven

11 18 Beaver Ridge Road, Morris Plains, NJ (973) Fax (973) system-dynamics.com system-dynamics.com For More Information: System Dynamics Inc.


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