Explain what is a CDN, its advantages, and how to exploit caching on the internet. I cover Akamai in specific, along practices around Cache Headers, Cookie less domains, Fingerprinting, etc. This talk was delivered at GIDS Bangalore (Apr 2015).

1. Harnessing the Power of CDNs
Gurpreet Luthra, Lead Consultant

2. Agenda
• What is a CDN?
• Brief on Akamai
• Advantages of a CDN
• Exploiting Caching
• Statistics & Numbers
• Architectural Considerations
• Further References

3. About Me - Gurpreet Luthra
• 13+ years, Developer & Lead Consultant
• Working on Scala
• Spent last few months harnessing Akamai
• Twitter: _zenx_

4. What is a CDN?
http://my-retail-store.com (GET)

5. What is a CDN?
Hash
Table
Cache for all your HTTP Get Requests
http://my-retail-store.com (GET)

6. What is a CDN?
Ha
Spread them all over the World!
Ha
Ha
Ha
Ha
Ha
Ha
ORIGIN

7. CDN Distribution Scheme
"NCDN - CDN" by Kanoha - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons
http://commons.wikimedia.org/wiki/File:NCDN_-_CDN.png#/media/File:NCDN_-_CDN.png

8. Examples of CDNs
https://hostingreview360.com/top-5-cdn-providers/

9. Examples of CDNs

10. • 15-30% of all Web Traffic
• $1.96 Billion Annual Revenue
• 5000+ employees
• 170,000 Servers in 102 countries
• 2 trillion daily Internet interactions
http://www.akamai.com/html/about/facts_figures.html

11. http://www.akamai.com/html/technology/real-time-web-monitor.html

12. How do I know if a website is
using Akamai?
12

13. 13

18. https://control.akamai.com/EdgeAuth/login.jsp

19. https://control.akamai.com/EdgeAuth/login.jsp

21. Recap — Why CDN?
• Caching: Reduced Page Construction Time
• Closer: Reduced Latency
• Traffic Offloaded: Reduced Loads
• Backup: Served even if site is down
• Protection: Prevent DoS Attacks
• Others: Redirects/Auto-compression/Best-route
detection

23. Types of Caches on the Internet
• Web browser
• Proxy
• CDNs
• Reverse Proxies
• Web Server’s / Specialized Caches

24. What would we love?
• Cache Forever
• Deploy immediately

25. So… Exploit Caching…

26. HTTP Response Cache Headers
• Expires
• Cache-Control
• Last-Modified
• ETag

27. cache-control
• max-age= (seconds)
• s-maxage=
• public
• private
• no-cache
• must-revalidate
• proxy-revalidate
https://www.mnot.net/cache_docs/#CACHE-CONTROL

28. https://redbot.org/

30. Fingerprinting
• Javascripts
• CSS
• Assets
http://server.com/css/global-908e25f4bf641868d8683022a5b62f54.css

31. Fingerprinting
HTML Pages Not
fingerprinted
5 - 30 mins
JS/CSS/Assets Fingerprinted 1 year
Images 30 days - 1 year

34. Cookie-less Domain
• Why submit cookies for every GET request
for assets?
http://my-assets-host.com/css/
global-908e25f4bf641868d8683022a5b62f54.css

35. Caching & SSL?
http://www.akamai.com/dl/feature_sheets/fs_edgesuite_securecontentdelivery.pdf

36. Impact on one Website
• 85% - 90% Traffic offloaded to Akamai
• MONTH
• Assets: 100 GB (3KB Cookie)
• Assets: 16 Million requests
• Traffic: 47 TB (Akamai)
• Traffic: 4 TB (Origin)
• Peak: 742 Hits/sec (Akamai)
• Peak: 47 Hits/sec (Origin)

37. Architectural Considerations
• Page Fragments
• User Centric Data - Client Side - AJAX
• Mobile/Non-Mobile Views in one payload

38. FROM: http://ahcdn.com/en/

39. Further References
• The minimum about Web caching you should know: https://
www.mnot.net/cache_docs
• http://www.mobify.com/blog/beginners-guide-to-http-cache-
headers/
• http://guides.rubyonrails.org/asset_pipeline.html
• http://www.ietf.org/rfc/rfc2616.txt (Section 14.9)
• http://ocw.mit.edu/courses/mathematics/18-996-topics-in-
theoretical-computer-science-internet-research-problems-
spring-2002/lecture-notes/
• http://www.akamai.com/dl/technical_publications/
GloballyDistributedContentDelivery.pdf
• Image Credits: http://publicdomainvectors.org/

40. 40

41. Gurpreet Luthra
http://techie-notebook.blogspot.com
_zenx_