Change network availability to all users

enterprise network availability monitoring system and high availability network fundamentals pdf
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Published Date:19-07-2017
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Availability, Survivability, Protection/Restoration, Fast Re- Route Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1Market Drivers for Survivability  Customer Relations  Competitive Advantage  Revenue  Negative - Tariff Rebates  Positive - Premium Services Business Customers Medical Institutions Government Agencies  Impact on Operations  Minimize Liability Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 4Network Survivability: drivers  Availability: 99.999% (5 nines) = less than 5 min downtime per year  Since a network is made up of several components, the ONLY way to reach 5-nines is to add survivability in the face of failures…  Survivability = continued services in the presence of failures  Protection switching or restoration: mechanisms used to ensure survivability Add redundant capacity, detect faults and automatically re-route traffic around the failure  Restoration: related term, but slower time-scale  Protection: fast time-scale: 10s-100s of ms…  implemented in a distributed manner to ensure fast restoration Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5Failure Types & Other Motivations  Types of failure:  Components: links, nodes, channels in WDM, active components, software…  Human error: backhoe fiber cut Fiber inside oil/gas pipelines less likely to be cut  Systems: Entire COs can fail due to catastrophic events  Protection allows easy maintenance and upgrades :  Eg: switchover traffic when servicing a link…  Single failure vs multiple concurrent failures…  Goal: mean repair time mean time between failures…  Protection also depends upon kind of application:  SONET/SDH: 60 ms (legacy drop calls threshold)  Do data apps really need this level of protection?  Survivability may hence be provided at several layers Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6Network Survivability Architectures Network Survivability Architectures Restoration Protection Self-healing Re-Configurable Protection Switching Network Network Linear Protection Ring Protection Mesh Restoration Architectures Architectures Architectures Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7Network Availability & Survivability Availability is the probability that an item will be able to perform its designed functions at the stated performance level, within the stated conditions and in the stated environment when called upon to do so. Reliability Availability = Reliability + Recovery Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8Quantification of Availability Percent N-Nines Downtime Time Availability Minutes/Year 2-Nines 5,000 Min/Yr 99% 99.9% 3-Nines 500 Min/Yr 4-Nines 50 Min/Yr 99.99% 5-Nines 5 Min/Yr 99.999% 99.9999% 6-Nines .5 Min/Yr Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 9PSTN : The Yardstick ?  Individual elements have an availability of 99.99%  One cut off call in 8000 calls (3 min for average call). Five ineffective calls in every 10,000 calls. PSTN End-2-End Availability 99.94% NI NI 0.005 % 0.005 % AN AN Facility Facility 0.01 % LE 0.01 % LE Entrance Entrance NI : Network Interface 0.005 % LE : Local Exchange LD 0.005 % LD : Long Distance 0.02 % AN : Access Network Shivkumar Kalyanaraman Rensselaer Polytechnic Institute Source : http://www.packetcable.com/downloads/specs/pkt-tr-voipar-v01-001128.pdf 10Services Determine the Requirements on Network Availability Source : www.t1.org Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 11IP Network Expectations Service Delay Jitter Loss Availability Real Time Interactive L L L H (VOIP, Cell Relay ..) Layer 2 & Layer 3 VPN’s M (FR/Ethernet/AAL5) H L L Internet Service H H M L Video Services L M M H L : Low M : Medium H : High Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 12Measuring Availability: The Port Method  Based on Port count in Network (Total of Ports X Sample Period) - (number of impacted port x outage duration) x 100 (Total number of Ports x sample period)  Does not take into account the Bandwidth of ports e.g. OC-192 and 64k are both ports  Good for dedicated Access service because ports are tied to customers. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 13The Port Method Example  10,000 active access ports Network  An Access Router with 100 access ports fails for 30 minutes.  Total Available Port-Hours = 10,00024 = 240,000  Total Down Port-Hours = 100.5 = 50  Availability for a Single Day = (240000-50/240,000)100 = 99.979166 % Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 14The Bandwidth Method  Based on Amount of Bandwidth available in Network (Total amount of BW X Sample Period) - (Amount of BE impacted x outage duration) x 100 (Total amount of BW in network x sample period)  Takes into account the Bandwidth of ports  Good for Core Routers Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 15The Bandwidth Method Example  Total capacity of network 100 Gigabits/sec  An Access Router with 1 Gigabits/sec BW fails for 30 minutes. Total BW available in network for a day = 10024 = 2400 Gigabits/sec Total BW lost in outage = 1.5 = 0.5 Availability for a Single Day = ((2400-0.5)/2,400)100 = 99.979166 % Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 16Defects Per Million  Used in PSTN networks, defined as number of blocked calls per one million calls averaged over one year. (number of impacted customers x outage duration) -6 x 10 DPM = (total number of customers x sample period) Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 17Defects Per Million Example  10,000 active access ports Network  An Access Router with 100 access ports fails for 30 minutes.  Total Available Port-Hours = 10,00024 = 240,000  Total Down Port-Hours = 100.5 = 50  Daily DPM = (50/240,000)1,000,000 = 208 Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 18Basic Ideas: Working and Protect Fibers Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 19Protection Topologies -Linear  Two nodes connected to each other with two or more sets of links Working Protect Working Protect (1+1) (1:n) Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 20Protection Topologies -Ring  Two or more nodes connected to each other with a ring of links Line vs. Drop interfaces East vs. West interfaces W E D L E L W Working Protect W E E W Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 21Protection Topologies -Mesh  Three or more nodes connected to each other Can be sparse or complete meshes Spans may be individually protected with linear protection Overall edge-to-edge connectivity is protected through multiple paths Working Protect Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 22