This teaching material is a part of e-Photon/ONe Master study in

1. This teaching material is a part of e-Photon/ONe Master study in Optical Communications and Networks Course and module: Optical network resilience Quality of Resilience Authors: Piotr Chołda, AGH-UST, cholda@kt.agh.edu.pl Andrzej Jajszczyk, AGH-UST, jajszczyk@kt.agh.edu.pl Krzysztof Wajda, AGH-UST, wajda@kt.agh.edu.pl

2. Outline • Introduction • Motivation for the differentiation • Factors used as a differentiation basis • Differentiation frameworks proposed so far • Summary: comparison of the presented frameworks • An example: QoR concept • Possible extentions of QoR

3. Motivation for the differentiation „Classical approach” Input traffic „QoR” approach Input traffic QoS QoR • Main motivation: to incorporate and compare many resilience concepts • Resilience as a new dimension in service characterization (besides QoS also QoR is included in SLA) QoS

4. Parameters used for the differentiation • Mean Up Time • Downtime • Availability • Relative quality of the backup path • Affected traffic • Resilience to single/multiple failures • Preemption • Cost of the recovery • Failure coverage

5. Frameworks proposed so far • Reliability of Service (RoS) • Resilience Classes (RC) • Class of Service (CoS) • Differentiated Reliability (DiR) • Quality of Protection (QoP) • Quality of Reliability (QoR) • Quality of Service Protection (QoSP)

6. Reliability of service, RoS • Four classes defined qualitatively: • Guaranteed protection • Best effort protection • Unprotected traffic • Preempted traffic • Advantage: simplicity • Disadvantage: difficulties with the differentiation of subtle methods

7. Resilience classes, RC • Quality aspects are added

8. Class of service, CoS • The differentiation is based on the combination of some factors

9. Differentiated Reliability, DiR • Quantitative approach • Maximum Failure Probability (MFP) is assessed for each connection • Advantage: not only qualitative approach • Disadvantage: MFP is too strict factor it forces the used scheme

10. Quality of Protection, QoP • Based on RoS framework • The difference (from the previous one): quantitative approach • QoP – the probability of surviving a failure • The differentiation • Guaranteed protection: QoP=1 • Best effort protection: 0<QoP<1 • Unprotected traffic: QoP=0 • Preempted traffic: -1<QoP<0

11. Quality of Reliability, QoR • Quantitative approach based on the recovery time differentiation • Infinite number of classes • Classes are related to the linear function of recovery times • The lowest class: minimum recovery time • Higher classes

12. Quality of Service Protection, QoSP • Quantitative approach based on the combination of some factors • Packet loss • Recovery time • Resources used

13. Comparison of proposed frameworks

14. Quality of Resilience proposal, QoR The proposal made originally within NOBEL project and further developed within e-Photon/ONe+ Main goal: to introduce single combined measure for assessment of quality of recovery and to share information about failures between users and operator

15. QoR framework • Assumptions • Methodology is related to connection-oriented technology (especially MPLS and its derivatives) • QoR is calculated for particular LSPs • Parameters used as components • Probability that LSP fails availability of a connection, A • Transmission quality degradation after failure quality of the backup path, Q • Inconvenience related to the recovery switching recovery time, T • Cost of the recovery bandwidth redundancy, R • Imperfections connected with recovery affected traffic, L

16. QoR – description of methodology For each of initially chosen recovery schemes • ABSTRACTION: calculation of values describing network • Output: vector of real parameters • NORMALIZATION of values • Output: vector of normalized parameters

17. QoR - rationale • APPLICATIONs: • QoR measure in broader sense: comparison of different procedures for optimization purposes useful mainly for carriers • QoR measure in stricter sense:study of interdependencies between selected parameters better network behavior understanding • Supervision of SLAs client-operator relationship • Study of „quality cuts” client-operator relationship • QoS routing network control

18. What QoR can be? • Quality of Resilience must/should address the following problems: • Service differentiation on the basis of the resilience • Quantification of resilience parameters • Tailoring of recovery methods to different service classes/applications’ requirements • Service Level Agreement resilience parameters preparation • Additional operational strategies in specific cases (such as preemption)

19. QoR – further steps • General concepts and methods • Elaboration of different parameters quantification • Reliability models • Recovery time PDF quantification and statistical investigations • Specification of the mutual relation between QoS and QoR • Studies on selected recovery methods/scenarios/contexts (case studies) • E.g., continuation on QoR in VoIP studies (real-time services) • E.g., QoR in umbrella scenario • ...

20. QoR – further steps (2) • application of control/management plane mechanisms enabling the usage of more than one recovery mechanisms • the percentage of connections related to different service classes, • amount of spare resources in a network, • topology of a network. • ...

21. QoS/QoR relation for real-time services • New parameters are added to the SLA • Additional Quality of Service (QoSR) • If QoSR fulfilled the service is available • QoR parameters that characterize the downtime QoS Service class parameters QoR • QoSR • Packet loss ratio • QoR parameters • MTTR • MTBF • QoS parameters • Delay • Jitter • BER • Traffic load • Packet loss ratio

22. QoR – modified attitude to service availability • The service state model • There are two states: • the service is available • the service is unavailable • QoSR and the QoS parameters are the same in most of the cases QoSR QoS Available (A) Unavailable (1-A) The service is available The service is unavailable broken degraded QoS compliant degraded unavailable degraded available