Doing Horrible Things with DNS - Web Directions South
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Doing horrible things to DNS involves using CNAME records to create multiple domain names that resolve to the same IP addresses. This allows making a single DNS query but receiving responses for multiple domains, enabling more parallel HTTP requests. The technique involves creating a chain of CNAME records that ultimately resolve to a single canonical name, gaining the ability to load resources from different apparent hostnames while only requiring one DNS lookup.
Doing Horrible Things with DNS - Web Directions South
- 1. Doing Horrible Things to DNS (in the name of science) @sh1mmer Yahoo! Inc
- 2. The basics of DNS
- 10. San Francisco - Mission Branch
- 13. San Francisco - Main Library
- 16. New York City - 5th & 42nd Branch
- 19. New York City - 5th & 42nd Branch
- 21. NYC San Francisco - Main Library
- 22. San Francisco - Main Library
- 24. NYC SF San Francisco - Mission Branch
- 25. San Francisco - Mission Branch
- 27. NYC SF Mission
- 29. NYC SF Mission Me
- 31. GTFO! It's 3am!
- 33. Page Load Time vs. Bandwidth
- 34. Page Load Time vs. Round Trip Time
- 35. Trend Curves for Bandwidth vs. RTT
- 36. Serial HTTP loading - 1 domain
- 37. Parallel HTTP loading - 3 domains
- 38. So why not just use a loads of domains?
- 39. DNS Lookup
- 40. Ideal? 1 DNS query many parallel threads
- 41. Option 1: SPDY (by Google)
- 42. Good: Multi-thread TCP connections Bad: Only works on Chrome :(
- 43. Option 2: Do horrible things to DNS
- 44. Mucking about with C names
- 45. CNAMES are hosts which are aliases of other hosts
- 46. enki:~ $ dig yahoo.com ; <<>> DiG 9.4.3-P3 <<>> yahoo.com ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32801 ;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 7, ADDITIONAL: 7 ;; QUESTION SECTION: ;yahoo.com. IN A Query ;; ANSWER SECTION: yahoo.com. 5935 IN A 69.147.125.65 yahoo.com. 5935 IN A 72.30.2.43 yahoo.com. 5935 IN A 98.137.149.56 yahoo.com. yahoo.com. 5935 5935 IN IN A A 209.191.122.70 67.195.160.76 Response ... ;; Query time: 45 msec ;; SERVER: 202.171.190.10#53(202.171.190.10) ;; WHEN: Wed Oct 13 17:23:39 2010 ;; MSG SIZE rcvd: 345
- 47. ajax1.hackerhouse.org. 1800 IN CNAME ajax2.hackerhouse. ajax2.hackerhouse.org. 1800 IN CNAME ajax3.hackerhouse. ajax3.hackerhouse.org. 1800 IN CNAME ajax4.hackerhouse. ajax4.hackerhouse.org. 1800 IN CNAME ajax.hackerhouse. ajax.hackerhouse.org. 1800 IN A 192.168.1.1 ajax.hackerhouse.org. 1800 IN A 192.168.1.2 ajax.hackerhouse.org. 1800 IN A 192.168.1.3 ajax.hackerhouse.org. 1800 IN A 192.168.1.4 ajax.hackerhouse.org. 1800 IN A 192.168.1.5
- 48. We now have 5 hostnames with 1 DNS query
- 49. 5 hostnames x 6 request per host = 30 parallel requests
- 50. Doing Horrible Things to DNS (in the name of science) Questions? @sh1mmer Yahoo! Inc