1. CS193H: High Performance Web Sites Lecture 21: Vol 2 – Split Dominant Domains Steve Souders Google souders@cs.stanford.edu

2. announcements Handouts of Vol 2 chapters 1-4 are available in class and at office hours. Copies are being sent to SCPD students. DO NOT COPY OR DISTRIBUTE THESE HANDOUTS!

3. Examples http://stevesouders.com/hpws2/domains1.php http://stevesouders.com/hpws2/domains2.php HTTP/1.1 and older browsers 2 connections per server based on name, not IP includes IE 6,7 "domain sharding" intentionally splitting resources across multiple domains makes pages load faster

4. Split dominant domains but Rule 9 says "Reduce DNS lookups"?! remove DNS lookups that aren't heavily used split domains that are on the critical path how find "critical path"?

5. www.yahoo.com

6. http://news.google.com news.google.com

7. Downgrading to HTTP/1.0 HTTP/1.1 – 2 connections/server HTTP/1.0 – 4 (IE 6,7), 8 (FF2) conns HTTP/1.1 has fewer connections because persistent connections are on by default best for static content example: http://www.aol.com/http://www.aol.com/

8. newer browsers http://stevesouders.com/ua/ http://www.stevesouders.com/blog/2008/03/20/round up-on-parallel-connections/ HTTP/1.1HTTP/1.0 IE 6,726 IE 866 Firefox 1.5, 228 Firefox 366 Safari 3,444 Chrome6? Opera 94?

9. how many domains? http://yuiblog.com/blog/2007/04/11/performance- research-part-4/ 2-4 is optimal after 4 domains, response time degrades more DNS lookups thrashing on client

10. Homework 12/1 11:59pm – Assignment #6 - Improving a Top Site rules 11-14 Vol 2: Split the Initial Payload Load Scripts Without Blocking Don't Scatter Inline Scripts Shard Dominant Domains Optimize Images

11. Questions What's "domain sharding"? Why would downgrading to HTTP/1.0 be faster? Should I do that for all responses? Why would the HTTP/1.1 spec suggest fewer connections per server? What's the # of connections per server for popular browsers? What's the optimal number of domains to shard across?