1. Measuring Availability in Telecommunications Networks Mattias Thulin, November 2004

2. Disposition 1. Introduction 2. Method 3. Network Availability 4. SDH Network description 5. ITU-T standard G.826 6. Analysis 7. Implementation 8. Result 9. Conclusions 2

3. Song Networks Nordic network provider Optical fiber network covering Northern Europe Products: IP-VPN Internet connections Telephone services Hosting Carrier services

4. Introduction Market demand for network quality Important to measure network availability Maintain service-level agreements Attract new customers Indicator of network quality for internal maintenance Methods of measuring and defining Network Availability vary between operators

5. Purpose How is Network Availability defined? How can it be measured? Why should it be measured? What standards exist? Are there any recommended values for availability parameters? How can availability measurements be applied to Song Networks SDH transmission network?

6. Delimitations 1) General study on Network Availability 2) Develop a method for availability measurement Nortel SDH equipment Four rings 44 links Oriented towards network-operation

7. Method Literature study Network study Monitoring system Preside Interviews Standards Design model for availability measurement and presentation

8. Network Availability - definition The ability of a functional unit to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval, assuming that the required external resources are provided. ISO 2382-14, 1997

9. Network Availability – The “five-nines” Percentage value of uptime for a given time period “Five-nines” 99,999% Viewed as desired uptime in network core-level AvailabilityDowntime per year 99,9999%32s 99,999%5min 15s 99,99%52min 36s 99,9%8h 46min 99%3 days 15h 40min

10. Theoretic Availability Summing availability

11. Reactive Availability Data from trouble-tickets Good for measuring customer-experienced availability Easy to identify what equipment failed and what solved the error Can lack information of short interruptions and outside of office hours

12. Customer- vs. Network-management oriented Important to know for whom or for what purpose are we measuring Customer oriented Includes all layers Calculate downtime when the customer connection is not working. Network-management oriented What links have lower availability? Considered as downtime although the traffic is rerouted

13. SDH Network Description SDH – Synchronous Digital Hierarchy Based on American standard SONET Normally build in ring structure Error correction and retransmission is done by overlaying protocols

14. Song Networks’ SDH network Baltic ring Nordic ring Europe ring Sweden ring

15. Song Networks’ SDH network Sweden ring: 9 Network Elements Nordic ring: 7 Network Elements European ring: 7 Network Elements Baltic ring: 3 Network Elements

16. Surveillance and statistics OPC NE Preside NE

17. Preside Global performance Alarm lists Query performance statistics

18. Preside log files Comma-delimited text files (CSV) One file per Network Element 96 15-min counts (past 24 hours) 8 24-hour counts (past week) 1200,Ottawa,OC48,Term,DS3,G7,2,Line,Rx,Ne,SES,03/07/99,03/0 7/99,16:00, 0,0,0,2,3,8,12,6, 0,0,1,0,0,0,0,1,0,0,0,2,0,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0

19. ITU-T Standard G.826 Errored Block (EB)  1 bit-error/block Errored Second (ES) 1 sec with  1 EB Severly Errored Second (SES) 1 sec with  30% EB Bit-error Parameters:

20. Unavailable Second (UAS) A period of unavailable time begins at the onset of ten consecutive SES events. These ten seconds are considered to be part of unavailable time. A new period of available time begins at the onset of ten consecutive non-SES events. These ten seconds are considered to be part of available time. (ITU-T G.826, 2002)

21. Analysis Define availability Develop model for calculating average availability Define database structure for saving availability statistics Specify format for availability reports

22. Analysis Follow ITU-T Standard G.826 Apply to all active links in the network Calculate average availability per link, per ring and total network Present first five significant figures First calculate average UAS, convert to percentage in last step to avoid rounding error

23. Analysis + + 3 Availability for a ring is the average UAS for all the links in the ring

24. Implementation Database Log Files ParserAnalyze Report

25. Implementation - parser program Programmed in Java for platform independence Parse all log-files in directory for: NE Link Day UAS count Insert into MySQL database table

26. Implementation – report generating Web interface for easy access Input parameters: start and end date PHP-script query database for UAS values and calculate average availability Per link Per ring Total network Report can be saved to PDF format (PHP-script)

27. Implementation – Graphic reports Crystal Reports Start-date and end-date are entered and the program queries database and produces graphic reports Can be exported to PDF file

28. Result Between 2004-07-12 and 2004-09-19 SDH RingAvailability in % Sweden DX99.983 Nordic DX99.997 Europe DX99.462 Baltic DX99.814 TOTAL99.81 NELinkAvailability in % 6052G1199.989 6052G1299.989 6052G1799.944 6052G1899.958 6053G1799.856 6053G1899.959 6054G17100 6054G1899.95 6056G1199.989 6056G12100 6056G1799.951 6056G18100 6060G11100 6060G12100 6060G17100 6060G1899.993 6058G1799.993 6058G18100 6044G11100 6044G1299.989 6044G17100 6044G18100 6045G17100 6045G18100 6046G17100 6046G18100

29. Result Between 2004-07-12 and 2004-09-19

30. Result Between 2004-07-12 and 2004-09-19

31. Conclusions Background study can be used for planning future measurements Positive feedback from network operations management for the weekly reports Need more statistic in the database to observe general trends By studying trends Song Networks can cut maintenance spending and better forecast future cost by directing resources to maintain a high network quality Future work: Measure backbone availability from a customer point of view using relational databases How do errors in the backbone affect distribution layer?

32. Questions?