Telecomunicazione. A Priority-Aware Protection Technique for QoS Enabled WDM Networks

Transcription

1 Uiversità di Bergamo Facoltà di Igegeria dell Iformazioe e etodi atematici La Protezioe elle Reti di Telecomuicazioe A Priority-Aware Protectio Techique for QoS Eabled WD etworks Fabio artigo

2 Sommario Itroduzioe Strategie di Protezioe classiche Priority-Aware Shared-Protectio odelli atematici e risultati umerici Iterpretazioe dei risultati

3 Resiliece i WD etworks The maturig of WD techology: A sigle fiber carries huge amout of data Terabit/s The failure of a etwork compoet: Ca lead to huge loss i data ad reveue Solutio: Protectio a proactive procedure to recover traffic whe a failure occurs: Oe path is referred to as primary path used to carry traffic durig ormal operatio. Extra backup resources are pre-reserved ad activated whe the primary path fails.

4 Challeges The operator is faced by several challeges: Satisfy the QoS requiremets of the cliet defied through a SLA Service Level Agreemet: A SLA Violatio may cause a certai amout of pealty to be paid by the operator. Out of service criterio Recovery time with degraded SLA Full recovery time Service uavailability Premium Degraded BER0-4 ot spec. 50 ms 0-5 old Degraded BER ms 300 ms 0-4 Silver Fault LOS 500 ms 5 sec Broze Fault LOS 5 sec 5 mi At the same time select a cost effective protectio scheme to achieve this goal

5 Why do we protect? Protectio is ormally doe for the purpose of icreasig the availability of the ed-to-ed coectio. Availability: Availability fractio of time the coectio is up durig etire service time uit: mis/year Availability available Time/available Time+ dow time. Protectio does help to icrease availability: Traffic o failed primary path will be switched to the backup path The more backup resources we have the greater will be the availability

6 Availability Each etwork compoet is characterized by its availability which depeds upo: Failure rate: ea Time To Failure TTF /Lambda Failure recovery rate: ea Time To Repair TTR /u 5042 FIT/000 miles FITFailure I Time how may failures the compoeet experieces i 0 9 hours

7 Availability 2 Path availability: Product of i betwee compoets availability Where: A t A i i A i TTF/TTR + TTF ai reaso for failure is related to fiber liks

8 Availability 3

9 First Coclusio To reach the 5 9 s objective for log distace coectios we eed to protect the sigal Several protectio schemes exist i the literature: Each oe has its ow advatage ad disadvatage. The most commo: Dedicated Protectio Shared Protectio Still we do t kow with each protectio scheme what is the resultig availability: We ted to combie the advatages from both approaches to use resources efficietly while meetig user s requiremet

10 Dedicated Protectio X Y S D B C Dedicated Protectio: : or +

11 Dedicated Protectio Y Z W X S D B C Dedicated Protectio: 2:

12 Dedicated Protectio Aalysis Advatages Availability is icreased by several orders of magitude Excludig the multiple cocurret failure sceario Availability 00% Drawbacks: Resource redudacy 00%

13 Shared Protectio X Y S D E F B C Shared Protectio

14 Shared Protectio Aalysis Advatages Less resources are eeded for protectio compared to dedicated protectio case Drawbacks: Less Availability is obtaied i case of multiple failures

15 Our Propositio Priority-Aware Shared Protectio Scheme

16 Priority-Aware Shared Protectio A ew scheme exploitig the advatage of dedicated ad shared protectio may be realized Istead of equally treatig the coectios sharig the protectio chael: A otio of service differetiatio may be itroduced So old coectios ad S Silver coectios may share the same backup path. old coectios ca preempt Silver oes i the utilizatio of backup resources.

17 athematical odels For both Classical ad Priority Aware protectio Schemes We compute the Availability for every coectio

18 We have workig paths protected by a sigle protectio path The system ca be modeled with a arkov Chai havig + states State i i paths icludig Workig ad Protectio paths are dow Steady State Probability: Aalysis of : protectio without Service Differetiatio µ µ µ 2µ 3µ 4µ A A p ρ ρ ρ ρ ρ µ ρ µ ea Repair Rate ea Failure Rate!!! + +

19 Aalysis of : protectio without Service Differetiatio Performace of the : Protectio Scheme: ea Uavailability: U µ + 2 p ello stato per >2 ci soo ifatti - coessioi o protette sul totale delle coessioi La probabilità che ello stato ua coessioe scelta a caso fra le sia proprio tra le - o protette è data dal rapporto -/

20 We have old coectios Silver coectios ea Uavailability for the old ad Silver Coectios: Aalysis of : protectio with Service Differetiatio + 2 p U µ S S U U U µ µ µ S Le coessioi old è come se o vedessero eache quelle Silver viste che possoo preemptarle ell occupare il cammio di backup. Quidi l uavailability U di ua coessioe old è pari a quella di ua coessioe i u sistema co protezioe : L uavailability totale U si coserva.

21 We have Protectio paths protectig Workig paths We model the system with a arkov Chai with + states State i i paths icludig Workig ad Protectio paths are dow Steady State Probability: Aalysis of : protectio without Service Differetiatio A A p ρ ρ ρ ρ ρ µ +-µ µ 2µ 3µ 4µ

22 Aalysis of : protectio without Service Differetiatio Performace of the : Protectio Scheme: ea Uavailability: U µ + + p ello stato per >+ ci soo ifatti - coessioi o protette sul totale delle coessioi La probabilità che ello stato ua coessioe scelta a caso fra le sia proprio tra le - o protette è data dal rapporto -/

23 We have old coectios Silver coectios ea Uavailability for the old ad Silver Coectios: ea Frequecy of Failure for the old ad Silver Coectios: Aalysis of : protectio with Service Differetiatio + + p U µ S S U U U µ µ µ S + p F µ S S F F F µ µ µ

24 umeric Results Based o the mathematical we defied for each protectio scheme the resultig availability

25 umeric Results: :3 Protectio The Priority-Aware scheme allows the provisioig of oe Platium coectio % which was impossible with the classical scheme. Two old coectios ca be provisioed Availabilty > 99.99%

26 umeric Results: : Protectio 800 km The Priority-Aware scheme allows the deploymet of oe Platium coectio % for every value of - old coectios ca be provisioed Availability > 99.99%

27 Coclusios We proposed a improvemet of the classical shared protectio based o relative priorities We developed a detailed mathematical model to gauge the impact of our propositio We showed that service differetiatio is better achieved through the use of our proposed protectio scheme We developed a simulatio study showig that the proposed scheme achieves high Availability Satisfactio Rates while realizig cost-effectiveess i terms of resource usage i the etwork.