Slides12 - 1 Survivable Network Design Survivable Network...

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Unformatted text preview: 1 Survivable Network Design Survivable Network Design David Tipper Graduate Telecommunications and Networking Program University of Pittsburgh Telcom Telcom 2110 Slides 12 2110 Slides 12 Causes of Network Outages According to Sprint a link outage in IP backbone every 30 min on average Accidents cable cuts car wreck etc cable cuts, car wreck, etc. According to AT&T 4.39 Cable cuts / year / 1000 km Human errors incorrect maintenance, installation Environmental hazards fire, flood, etc. Sabotage physical, electronic Operational disruptions schedule upgrades, maintenance, power outage Hardware/Software failures Line card failure, faulty laser, software crash, etc. 2 IP Backbone Failure 9% 9% Other Unknown Other Unknown 32% 32% 23% 23% 36% 36% Time to Recover from Layer 1 failure Congestion Software Upgrade Hardware Upgrade Configuration Errors Link Failure Link Failure Router Operations Router Operations Source: University of Michigan, 2000 23% 23% Software failures Hardware failures DOS Attacks Router Failures Router Failures Network Survivability Definition Ability of the network to support the committed Quality of Services (QoS) continuously in the presence of various failure scenarios Survivability Components Analysis : understand failures and system functionality after failures Design : adopt network procedures and architecture to prevent and minimize the impact of failures/attacks on network services. Goal: maintain service for certain scenarios at reasonable cost Self Healing network 3 Survivable Network Design Three steps towards a survivable network 1. Prevention: Robust equipment and architecture (e.g., backup power supplies) Security (physical, electronic), Intrusion detection, etc. 2. Topology Design and Capacity Allocation Design network with enough resources in appropriate topology Spare capacity allocation to recover from failure 3. Network Management and traffic restoration procedures D t t th f il d t t ffi d f il i th Detect the failure, and reroute traffic around failure using the redundant capacity Survivability Basic Concepts Working path and Backup path (recovery path): Working path : carry traffic under normal operation Backup path : an alternate path to carry the traffic in case of failures 3 4 Working route 1 3 4 2 X B A Backup route DCS Customer Backup route 4 Survivability Basic Concepts To survive against a network failure working path and backup path must be disjoint So that both paths are not lost at the same time So that both paths are not lost at the same time Disjoint = ? (depending on a failure scenario) Link disjoint Node disjoint (Shared Risk Link Group) SRLG disjoint Source Destination AP BP AP BP Source Destination Link-disjoint Node-disjoint Shared Risk Link Group (SRLG) C A Logical intent Actual routing Physical Cables...
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Slides12 - 1 Survivable Network Design Survivable Network...

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