Enhanced Network Topology For Improved System Availability - - PowerPoint PPT Presentation

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Enhanced Network Topology For Improved System Availability - - PowerPoint PPT Presentation

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conference & convention enabling the next generation of networks & services Enhanced Network Topology For Improved System Availability Availability Mark Enright Tyco Electronics Subsea Communications conference & convention

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SLIDE 1 enabling the next generation of networks & services

conference & convention

Enhanced Network Topology For Improved System Availability Availability

Mark Enright

Tyco Electronics Subsea Communications

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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

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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 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.

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Outline

  • Introduction – Historical treatment
  • Availability 101
  • Cable Fault Data
  • Application of Principles on example Network Topologies

– Point to Point – Point to Point – Ring – Hybrid Ring

  • Sensitivity Analysis
  • Application to Terrestrial Routes
  • Real World Example
  • Conclusion
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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 Rates of the Cable Station Equipment – Estimated Ship Repairs: A calculation of the estimated number of ship repairs over the life

  • f the system based upon intrinsic failures
  • No Consideration given for extrinsic

failures (e.g. external aggression)

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Availability 101

MTTR MTTF MTTF A + = MTTF=109 / FIT

60 8766 ) 1 ( ∗ ∗ − = A O

...

2 1 Component Component series

A A A ∗ =

) 1 ( ) 1 ( 1

2 1 Path Path parallel

A A A − ∗ − − =

P(Failure) = λ = 1/MTTF

Reference: ITU Standards

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Cable Fault Data

  • 90% of Faults

extrinsic

  • Shallow water
  • ccurrence 10x that
  • f Deep water
  • “Average” of last 5

years:

0.5 0.6 0.7 0.8 0.9 er 1000 km Depth < 1000m Depth > 1000m

years: – 0.2 fault/1000km/yr Shallow – 0.02 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

0.1 0.2 0.3 0.4 2001 2002 2003 2004 2005 2006 2007 2008 2009 Faults per

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Application

  • Cable Fault hazard rate will be applied to 3

different network connectivity options

– Point to Point – Ring – Hybrid

MTTR for a fault includes the following components 1 day for mobilization 1 – 6 day transit time,

  • Each connectivity option will include a

regional network and a trans-oceanic network with the following length/depth profile assumptions: 1 – 6 day transit time, assuming a fault in the middle of the length under consideration and ship speed of 500 km/day 5 days for repair

Trans-Oceanic Regional Deep-Water (km) 4,600 1,500 Shallow Water (km) 850 1,500

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Point to Point

17 . 1000 850 . 1000 / 2 . = ∗ km yr km flts

hr MTTF 400 , 52 17 . / 8766 = = hr MTTR 168 ) 5 1 1 ( * 24 = + + =

Fault Type Availability Outage (min/yr) TransOceanic Shallow Water 0.9968 1,700 TransOceanic Deep Water 0.9970 1,600

hr MTTR 168 ) 5 1 1 ( * 24 = + + =

9968 . 168 52400 52400 = + =

−transoc shallow

A

yr hr O

transoc shallow

/ 28 8766 * ) 9968 . 1 ( = − =

−

Total Transoceanic Outage = 3250 min/yr Total Regional Outage = 2640 min/yr

Regional Shallow Water 0.9958 2,200 Regional Deep Water 0.99918 430

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Ring

System Type Availability Outage (min/yr) TransOceanic 0.999962 20 Regional 0.999975 13

As expected, Outage is significantly lower

Regional 0.999975 13

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Hybrid

Branching Unit Branching Unit Repeater Repeater

Line Terminating Equipment Line Terminating Equipment LTE LTE

Branching Unit Branching Unit Branching Unit Branching Unit Repeater Repeater Repeater Repeater

Line Terminating Equipment Line Terminating Equipment Line Terminating Equipment Line Terminating Equipment LTE LTE

Branching Unit Branching Unit Branching Unit Branching Unit

Outage is Significantly improved!

System Type Availability Outage (min/yr) TransOceanic 0.9969 1583 Regional 0.9991 440

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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%

Hybrid 6300 1583 16%

  • 51%

Regional Point to Point 3000 2638 0% 0% Ring 6000 13 100%

  • 100%

Hybrid 4500 440 50%

  • 83%
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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 – 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

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Terrestrial Application

  • The same principle can be applied

to submarine cable land routes which are also subject to external aggression

PFE Hut Route 1 PFE Hut Route 1

  • Switching can be automatic or

manual

BMH

Cable Station Route 2 Route 1

BMH

Cable Station Route 2 Route 1

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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 1995 2008

Source: Wikipedia

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Conclusion

  • While least expensive, Point to Point links suffer the greatest
  • utage
  • Ring Networks provide the best network availability however, at

the greatest cost 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

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SLIDE 17

2010

enabling the next generation of networks & services

conference & convention

Pacifico Convention Plaza Yokohama & InterContinental The Grand Yokohama 11 ~ 14 May 2010 www.suboptic.org The 7th International Conference & Convention

  • n Undersea Telecommunications