Introduction to Content Delivery Networks
Download as PPTX, PDF0 likes639 views
The document discusses the principles and practices of Content Delivery Networks (CDNs), highlighting their role in improving user experience by addressing issues like latency, packet loss, and server load. It outlines the advantages and disadvantages of CDNs, particularly focusing on their mechanisms for content replication and delivery through passive and active methods. Challenges in deploying CDNs include content replication, location decisions, and client direction towards replicas.
Introduction to Content Delivery Networks
- 1. Content Delivery Networks CS4482 High Performance Networking Dilum Bandara Dilum.Bandara@uom.lk Some slides extracted from "Content Delivery Networks - Principles & Practice" by Ravi Sundaram
- 2. Internet Content Providers End Users The Web – Simple on Outside…
- 4. Issues Latency Browser takes a long time to load pages Packet loss Browser hangs, user needs to hit refresh Jitter Streams are jerky Server load Browser connects but doesn’t fully load the page Bandwidth aggregation Broken/missing content 4
- 5. Solution – Content Delivery Networks (CDNs) Servers at Network Edge Content Providers End Users NAP NAP
- 7. CDNs A system of computing devices networked together (across Internet) that cooperate to deliver content to end users Pros Improved end-user experience Reduce latency, packet loss, & jitter Transparent to users Reduced network congestion Increased scalability Improved fault-tolerance Reduced vulnerability Reduced costs 7
- 8. CDNs (Cont.) Cons Application-level solution Reliance on a CDN provider ISPs vs. CDN providers 8
- 9. CDN Mechanisms Passive Through browser cache & proxies If content is static, not much investment is needed from content provider Significant fraction of HTTP objects uncatchable Need investment from content provider Provider lacks of control & customization Active Replicate content on a distribution network HTTP redirects DNS-based Provider has control & customization Low investment from content provider side 9
- 10. CDN Challenges How to replicate content? Where to replicate content? How to find replicated content? How to choose among know replicas? How to direct clients towards replica? 10
- 11. CDN 11
- 12. CDN Options – HTTP Redirects Origin server rewrites pages to serve content via CDN 12 Page that distributes content via CDN Traditional Web page on server
- 13. CDN Options – DNS Based 13 A. Su, D. R. Choffnes, A. Kuzmanovic, & F. E. Bustamante, “Drafting behind Akamai (travelocity- based detouring), “ ACM SIGCOMM Comput. Commun. Rev. 36, 4, Aug. 2006, pp. 435-446.
- 14. CDN Options Application based (HTTP redirects) Pros Application-level, fine-grained control Cons Additional load & high RTTs, hard to cache Naming based (DNS selection) Pros Well-suitable for caching, reduce RTTs Cons Request by resolver not client, request for domain not URL, hidden load factor of resolver’s population 14