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Reliable Network/Service Infrastructures. 1. Availability, Reliability and Survivability. What Is “High Availability”?.
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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%)
Leading Causes of Downtime • Change management • Process consistency • Communications • Links • Hardware Failure • Design • Environmental issues • Natural disasters Telco/ISP35% Power Failure14% Hardware Failure 12% Human Error 31% Unresolved 8% SOURCE: Graph Data: The Yankee Group, The Road to a Five Nines Network, Feb 2004.
THIS Is Better Than… Enterprise THIS, which Is Better Than… Service Provider Network Enterprise But what is beyond this??? THIS Enterprise Link/Circuit Diversity
Network Point of Presence/Data Center • Cable management • Power: Diversity/UPS • HVAC • Hardware placement • Physical security • Labeling • Environmental control systems 6 6 6
Network Design Network Complexity Technology Can Increase MTBF People, Process, and Politics Can Increase Complexity THIS DECREASES MTBF and Increases MTTR
Network Design Primary Design Considerations • Hierarchical • Modular and consistent • Scalable • Manageable • Reduced failure • Domain (Layer II/III) • Interoperability • Performance • Availability • Security
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)
3 1 Router Availability R1, R2, R3 and R4 16000/(16000+24) = 0.9985 Can Include Hardware + Software Components Availability of R1, R2 in Parallel with R3, R4 = 1 - ((1-0.997)(1 - 0.997)) = 0.99999104 2 Availability of R1, R2 and R3, R4 in Series = (0.9985´0.9985) = 0.997006 4 Network Availability = 99.999% Only Base on Device Availability Values; Link Availability Not Included Network Availability Calculation R2 R1 Router R1, R2, R3 and R4 MTBF = 16000 Hours MTTR = 24 Hours R3 R4
High Availability - Layered Approach Application Level Resiliency Global Server Load Balancing and positioning Gateways, gatekeepers, SIP servers, DB servers NSF/SSO,HSRP,VRRP, GLBP, IP Event Dampening , Graceful Restart (GR): BGP, ISIS, OSPF, EIGRP, OER, BGP multipath, fast polling, MARP, incremental SPF Protocol Level Resiliency Circuits, SONET APS, RPR, DWDM, Etherchannel, 802.1d, 802.1w, 802.1s, PVST+,Portfast, BPDU guard, PagP, LacP,UDLD, Stackwise technology, PPP, Transport/Link Level Resiliency Device Level Resiliency Redundant Processors (RP), Switch Fabric, Line Cards, Ports, Power, CoPP, ISSU, Config Rollback