1. 1111 Reliable Network/Service Infrastructures

2. 222 Availability, Reliability and Survivability AvailabilityReliabilitySurvivability The expected ratio of the system uptime to total elapsed time Empirical factor The probability of the system keep being available (not fail) over certain period of time. Empirical factor The capability of the system to continue its operation and fulfill its mission in a full or limited scale during failure Probabilistic – Expected time between failures – Expected time to recover Probabilistic – Expected time between failures Non-probabilistic – Assumes explicit failures of different span and magnitude

3. 333 AvailabilityDowntime per Year (24x7x365) 99.000% 3 Days15 Hours36 Minutes 99.500%1 Day19 Hours48 Minutes 99.900%8 Hours46 Minutes 99.950%4 Hours23 Minutes 99.990%53 Minutes 99.999%5 Minutes 99.9999%30 Seconds What Is “High Availability”? The ability to define, achieve, and sustain “target availability objectives” across services and/or technologies supported in the network that align with the objectives of the business (i.e. 99.9%, 99.99%, 99.999%)

4. 444 Leading Causes of Downtime SOURCE: Graph Data: The Yankee Group, The Road to a Five Nines Network, Feb 2004. Change management Process consistency Communications Links Hardware Failure Design Environmental issues Natural disasters Telco/ISP 35% Power Failure 14% Human Error 31% Hardware Failure 12% Unresolved 8%

5. 555 Link/Circuit Diversity Enterprise THIS Enterprise THIS, which Is Better Than… Service Provider Network But what is beyond this??? Enterprise THIS Is Better Than…

6. 666 Network Point of Presence/Data Center Cable management Power: Diversity/UPS HVAC Hardware placement Physical security Labeling Environmental control systems 666

7. 777 Technology Can Increase MTBF People, Process, and Politics Can Increase Complexity THIS DECREASES MTBF and Increases MTTR Network Complexity Network Design

8. 888 Hierarchical Modular and consistent Scalable Manageable Reduced failure Domain (Layer II/III) Interoperability Performance Availability Security Primary Design Considerations

9. 999 Examples of Hardware Reliability (Reliability Block Diagrams) Hardware Reliability = 99.938% with 4 Hour MTTR (325 Minutes/Year) Hardware Reliability = 99.961% with 4 Hour MTTR (204 Minutes/Year) Hardware Reliability = 99.9999% with 4 Hour MTTR (30 Seconds/Year)

10. 10 Network Availability Calculation Router R1, R2, R3 and R4 MTBF = 16000 Hours MTTR = 24 Hours Router Availability R1, R2, R3 and R4 16000/(16000+24) = 0.9985 Can Include Hardware + Software Components 1 Availability of R1, R2 in Parallel with R3, R4 = 1 - ((1-0.997)(1 - 0.997)) = 0.99999104 3 Availability of R1, R2 and R3, R4 in Series = (0.9985  0.9985) = 0.997006 2 Network Availability = 99.999% Only Base on Device Availability Values; Link Availability Not Included 4 R1 R4 R3 R2

11. 11 High Availability - Layered Approach Application Level Resiliency Redundant Processors (RP), Switch Fabric, Line Cards, Ports, Power, CoPP, ISSU, Config Rollback Circuits, SONET APS, RPR, DWDM, Etherchannel, 802.1d, 802.1w, 802.1s, PVST+,Portfast, BPDU guard, PagP, LacP,UDLD, Stackwise technology, PPP, NSF/SSO,HSRP, VRRP, GLBP, IP Event Dampening, Graceful Restart (GR): BGP, ISIS, OSPF, EIGRP, OER, BGP multipath, fast polling, MARP, incremental SPF Global Server Load Balancing and positioning Gateways, gatekeepers, SIP servers, DB servers Protocol Level Resiliency Transport/Link Level Resiliency Device Level Resiliency