conference & convention enabling the next generation of networks & services Enhanced Network Topology For Improved System Availability Mark Enright Tyco Electronics Subsea Communications
conference & convention enabling the next generation of networks & services Presenter Profile Mark Enright has been with Subcom for 22 years. During his career he has held positions in Manufacture, Project Management and R&D. In addition to his current System Design responsibilities, Mark’s team is also responsible for Qualification testing of terminal products including SIE; Technical Customer Support Hotline and Power Feed Equipment Mark Enright Managing Director – System Engineering Email: menright@subcom.com Tel: (+1) 732 578 7428
conference & convention enabling the next generation of networks & services Abstract The reliability metric of availability of undersea communications systems is typically only applied to terminal equipment, because the long Mean-Time- To-Repair of submerged plant would dominate the metric. In theory, it can encompass the effect of all failures, and in fact, availability is more appropriate than “ship repairs” to explore quantitatively various fault scenarios in the submerged plant. This presentation analyzes the effect of external aggression faults on a set of alternate network topologies designed to increase overall system availability.
conference & convention enabling the next generation of networks & services Outline • Introduction – Historical treatment • Availability 101 • Cable Fault Data • Application of Principles on example Network Topologies – Point to Point – Ring – Hybrid Ring • Sensitivity Analysis • Application to Terrestrial Routes • Real World Example • Conclusion
conference & convention enabling the next generation of networks & services Historical Treatment • Traditionally, the availability of a Submarine System has been separated into two components: – Circuit Availability: A calculation of the path availability based entirely upon the Failure Rates of the Cable Station Equipment – Estimated Ship Repairs: A calculation of the estimated number of ship repairs over the life of the system based upon intrinsic failures • No Consideration given for extrinsic failures (e.g. external aggression)
conference & convention enabling the next generation of networks & services Availability 101 MTTF MTTF=10 9 / FIT A MTTF MTTR P(Failure) = O ( 1 A ) 8766 60 = 1/MTTF A A A ... series Component 1 Component 2 A 1 ( 1 A ) ( 1 A ) parallel Path 1 Path 2 Reference: ITU Standards
conference & convention enabling the next generation of networks & services Cable Fault Data • 90% of Faults 0.9 extrinsic 0.8 • Shallow water 0.7 occurrence 10x that Depth < 1000m Faults per 1000 km 0.6 of Deep water Depth > 1000m 0.5 • “Average” of last 5 years: 0.4 – 0.2 0.3 fault/1000km/yr 0.2 Shallow 0.1 – 0.02 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 fault/1000km/yr Deep Side note: Rate of occurrence of shallow water faults has significantly improved over the time period, most likely attributable to improvements in burial
conference & convention enabling the next generation of networks & services Application • Cable Fault hazard rate will be applied to 3 MTTR for a fault includes different network connectivity options the following components – Point to Point – Ring 1 day for mobilization – Hybrid 1 – 6 day transit time, assuming a fault in the • Each connectivity option will include a middle of the length under regional network and a trans-oceanic consideration and ship network with the following length/depth speed of 500 km/day profile assumptions: 5 days for repair Trans-Oceanic Regional Deep-Water (km) 4,600 1,500 Shallow Water (km) 850 1,500
conference & convention enabling the next generation of networks & services Point to Point Fault Type Availability Outage (min/yr) 850 km 0 . 2 flts / 1000 km . yr 0 . 17 TransOceanic 0.9968 1,700 1000 Shallow Water MTTF 8766 / 0 . 17 52 , 400 hr TransOceanic 0.9970 1,600 Deep Water MTTR 24 * ( 1 1 5 ) 168 hr Regional Shallow 0.9958 2,200 Water 52400 A 0 . 9968 Regional Deep 0.99918 430 transoc shallow 52400 168 Water Total Transoceanic Outage = 3250 min/yr ( 1 0 . 9968 ) * 8766 28 / O hr yr shallow transoc Total Regional Outage = 2640 min/yr
conference & convention enabling the next generation of networks & services Ring System Type Availability Outage (min/yr) TransOceanic 0.999962 20 Regional 0.999975 13 As expected, Outage is significantly lower
conference & convention enabling the next generation of networks & services Hybrid Branching Branching Branching Branching Branching Branching Line Line Line Line Line Line Unit Unit Unit Unit Unit Unit Terminating Terminating Terminating Terminating Terminating Terminating Equipment Equipment Equipment Equipment Equipment Equipment Repeater Repeater Repeater Repeater Repeater Repeater LTE LTE LTE LTE Branching Branching Branching Branching Unit Unit Unit Unit System Type Availability Outage Outage is (min/yr) TransOceanic 0.9969 1583 Significantly improved! Regional 0.9991 440
conference & convention enabling the next generation of networks & services Summary of Results Length (km) Outage (min) Length Outage Trans-Oceanic Point to Point 5450 3256 0% 0% Ring 10900 20 100% -99% Hybrid 6300 1583 16% -51% Regional Point to Point 3000 2638 0% 0% Ring 6000 13 100% -100% Hybrid 4500 440 50% -83%
conference & convention enabling the next generation of networks & services Sensitivity Analysis • While example assumptions were intended to be representative of actual systems, each system will be unique – Will the conclusion be the same with different hazard rate or different ratio of shallow/deep water ? • Hazard Rate – As seen in the equation, the proportional change in outage will be directly proportional to the change in hazard rate • Change in Shallow water length – MTTR dominated by repair time, therefore affect is proportional to baseline • Change in Deep water length – MTTR dominated by transit time, outage will scale as one-half of the square of the length ratio
conference & convention enabling the next generation of networks & services Terrestrial Application • The same principle can be applied to submarine cable land routes which are also subject to external aggression PFE Hut PFE Hut Route 1 Route 1 BMH BMH • Switching can be automatic or Route 2 Route 2 manual Cable Station Cable Station
conference & convention enabling the next generation of networks & services Real World Application As can be seen, the recently installed TPE system uses a hybrid topology vs. the classic ring used for the TPC-5 system TPE 2008 1995 Source: Wikipedia
conference & convention enabling the next generation of networks & services Conclusion • While least expensive, Point to Point links suffer the greatest outage • Ring Networks provide the best network availability however, at the greatest cost • The topology which offers redundancy at the shore-ends, where the extrinsic hazard rate is highest, provides significantly improved network availability in a much more cost effective manner
2010 conference & convention enabling the next generation of networks & services The 7th International Conference & Convention on Undersea Telecommunications Pacifico Convention Plaza Yokohama & InterContinental The Grand Yokohama 11 ~ 14 May 2010 www.suboptic.org
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