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Engineering a Content Delivery Network Bruce Maggs
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Current Installations Network Deployment 160000+ Servers 1200+ Networks 95+ Countries
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Akamai Statistics Peak bit rate: 13.1 Tbps on 3/13/2013 Peak HTTP daily requests: 2.59 trillion on 9/23/12 560.1M unique IPv4 addresses connected to Akamai on 3/6/2012 683M in Q3 2012
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Part I: Services http://www.yahoo.comhttp://www.amazon.comhttp://windowsupdate.microsoft.comhttp://www.apple.com/quicktime/whatsonhttp://www.fbi.gov
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Design Themes RedundancyRedundancy Self-assessmentSelf-assessment Fail-over at multiple levelsFail-over at multiple levels Robust algorithmsRobust algorithms
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FirstPoint – DNS (e.g., Yahoo!) Selects from among several mirror sites operated by content providerSelects from among several mirror sites operated by content provider
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Embedded Image Delivery (e.g., Amazon) <html><head> Welcome to xyz.com! Welcome to xyz.com! </head><body> <img src=“ Welcome to our Web site! Welcome to our Web site! Click here to enter Click here to enter </body></html> http://www.xyz.com/logos/logo.gif”> http://www.xyz.com/jpgs/navbar1.jpg”> Embedded URLs are Converted to ARLs ak
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End User Akamai DNS Resolution Akamai High-Level DNS Servers 10 g.akamai.net 1 Browser’s Cache OS 2 Local Name Server 3 xyz.com’s nameserver 6 ak.xyz.com 7 a212.g.akamai.net 9 15.15.125.6 16 15 11 20.20.123.55 Akamai Low-Level DNS Servers 12 a212.g.akamai.net 30.30.123.5 13 14 4 xyz.com.com.net Root (Verisign) 10.10.123.55 akamai.net8 select cluster select servers within cluster
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Regions Live Streaming Architecture 1 2 3 4 x X X 1 2 3 4 x Satellite Downlink Entry Point Satellite Uplink Top-level reflectors Encoding
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SiteShield (www.fbi.gov) Content provider’s website Hacker! AKAMAIAKAMAI AKAMAIAKAMAI AKAMAIAKAMAI
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Part II: Failures 1.Hardware 2.Network 3.Software 4.Configuration 5.Misperceptions 6.Attacks
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Hardware / Server Failures Linux boxes with large RAM and disk capacity, Windows servers Sample Failures: 1.Memory SIMMS jumping out of their sockets 2.Network cards screwed down but not in slot 3.Etc.
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Akamai Cluster Servers pool resources RAM Disk Throughput
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View of Clusters hardware failure buddy suspended datacenter odd man out
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Network Failures E.g., congestion at public and private peering points, misconfigured routers, inaccessible networks, etc., etc., etc.
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Core Points Core point X is the first router at which all paths to nameservers 1, 2, 3, and 4 intersect.Core point X is the first router at which all paths to nameservers 1, 2, 3, and 4 intersect. X can be viewed as the straddling the core and the edge of the network.X can be viewed as the straddling the core and the edge of the network. X 1 234
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Core Points 500,000 nameservers reduced to 90,000 core points 90,000 core points 7,000 account for 95% end-user load
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Engineering Methodology C programming language (gcc). Reliance on open-source code. Large distributed testing systems. Burn-in on “invisible” system. Staged rollout to production. Backwards compatibility.
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Perceived Failures Examples 1.Personal firewalls 2.Reporting tools 3.Customer-side problems 4.Third-party measurements
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