Tech Chat: Technical Review of Dynamic Content Acceleration

Editor's Notes

• #2: Welcome to the latest CDNetworks’ Technical Chat. Today we will cover How to Accelerate Dynamic Content.
• #3: In the next 5 minutes (or so), we’ll go over the Internet, the challenges of fast, reliable content, and how a CDN can help you achieve these goals.
• #4: As background, the Internet is a collection of private networks that are interconnected with each other. Everything from big global Internet Service Providers (ISPs) like AT&T and Level3 to regional and local ISPs. They all interconnect with each other and must speak the same the language for content requests to traverse them. In most cases, content requests travel across multiple ISPs.
• #5: One of the biggest hurdles to great performance is distance. The further you are from the content, the longer it takes to see it. You have to make a request, then wait for the response. You can see the difference response times between cities that are close vs. those that are far away.
• #6: The second hurdle is reliability. There is so much traffic that sometimes a packet gets lost or dropped. This can happen at any point during send or receive. The web browser automatically notices this and requests it to be re-sent. This works, but causes slowness.
• #7: And third is that HTTP, what we all use to communicate over the Internet, is very “chatty”. There is a connection phase to ensure both sides are ready, then the file is transmitted (takes multiple round trips) and then the disconnection phase happens. The original designers created a very robust network that could survive multiple failures, but does not efficiently take advantage of today’s better performing networks. CDNs were designed to overcome all 3 of these challenges.
• #8: As background, there are 2 types of content, Static and Dynamic. The Twitter logo and graphics are static. They rarely change and we all see the same images. The Twitter feed, that is different for each of us, is Dynamic, always changing.
• #9: Here is a representation of how a web page works w/o a CDN. The user requests the home page, which results in individual requests to retrieve the logo image, the html, as well as big files and any dynamic content. This works just fine, but can be quite slow.
• #10: For dynamic content CDNs use a different approach. The CDNs that support Dynamic content, create a Super Highway to accelerate across the long distance, which is something that individual ISPs can’t do. In the next few slides, we’ll go into details on how this works.
• #11: The following slides are common techniques. Different CDNs use different techniques. Most CDNs don’t share their specific techniques. Bottom line: it’s the performance that matters
• #12: SSL traffic is increasing, due to the increasing importance of security across the internet. A CDN will host the SSL certificate at it’s edge server, which will speed up SSL negotiation, similar in concept to how caching works, but moving the content closer to the end user.
• #13: For the content itself, CDNs can use a number of techniques, like connection pooling and keep alive. In green on the right, the CDN will keep a couple of connections open from the CDN edge to the CDN shield and to the customer Origin. This means that when a request for new data comes in, a connection will be ready. In addition, CDNs make sure the connections stay open by sending “keep alive” messages to ensure the connection is open and performing at optimal levels.
• #14: The techniques show so far have dealt with service architecture. The protocols and defaults can also be optimized. This optimization can happen at the first, middle, and last mile. They optimizations can include: large windows, fast retransmit, optimal retransmission timeouts, and fast recovery.
• #15: In summary, CDNs were specifically designed to improve the performance, reliability and security of Internet content. Here is a typical example of an origin in a single datacenter with response times (in orange) at the top. In the middle, in blue, are response times for 3 datacenters (cloud hosting or co-location). And the performance and reliability of a global CDN that supports both dynamic and static acceleration is yellow.
• #16: www.cdnetworks.com