Content distribution network (CDN) services and related technologies help facilitate the distribution of content at lower cost or higher performance than traditional cloud services. This tip will discuss new capabilities in and uses for CDN.
Ease of scalability is one of the often touted benefits of the cloud. In theory, it is possible to scale up a cloud-enabled application by adding more servers as demand grows. While this can work smoothly up to a point, things can break down if usage grows too quickly. The user experience can suffer or break and costs can spiral out of control.
In general, CDN services make it easier to distribute content such as Web objects and downloads -- i.e., software and video -- using techniques such as Web caching, server-load balancing and request routing. Key CDN techniques include:
- Speeding the network performance by staging content closer to users
- Improving network performance by tweaking the TCP protocols
- Dynamically refactoring code or transcoding media so it is distributed more smoothly using HTTP and TCP
- Improving resiliency to massive cyberattacks using CDN with dedicated security capabilities
The changing face of CDN
A modern content distribution network can improve cloud application performance, scalability and resiliency. The definition of a CDN is evolving as vendors improve the ability to solve business problems with CDN ecosystems. Leading services including Amazon CloudFront, Akamai Technologies Intelligent Platform, Verizon EdgeCast Networks Edge Optimizer and others have begun bundling features together into integrated Internet acceleration offerings. These can include content management, front-end optimization and distributed caching.
"CDN means different things to different people," said Dan Rayburn, principal analyst of digital media at Frost & Sullivan. He sees CDN offerings moving toward deployment platforms rather than just tools for moving content between points.
Good examples of this trend include Level 3 buying Vyvx along with Verizon buying both EdgeCast and Uplynk for creating, capturing, transforming and delivering video. Meanwhile large cloud service providers like Microsoft with Azure and Amazon with CloudFront are starting to build out similar functionality, as well.
Automation between CDN ecosystem components will be a key factor in the evolution of CDN services moving forward. Rayburn explained, "Customers want something that is future proof. They don't want to invest a lot of money only to find out they have to redo the ecosystems because one component does not tie into another."
Merging dynamic content with CDN
Content distribution network services are starting to embrace tools for dynamic content with recent support added in for Amazon CloudFront as well as Akamai's acquisition of Blaze. This is good news for enterprise architects seeking to simplify deployment of content and applications for their business. "Targeting content and optimizing site performance are typically separate dimensions of the user experience issue," said Jim Davis, industry analyst with 451 Research LLC. "Tying both concepts together is a better way to go."
Enterprises are not just looking to leverage CDN for video distribution. They also need support for e-commerce, security and other services outside of traditional CDN. In order to differentiate their offerings, vendors are starting to focus on specific verticals and solution sets for emerging business problems, according to Rayburn.
Strategically staging content
Latency is clearly the biggest factor in network constraints on Web page loading, said Guy Podjarny, chief product architect at Akamai. Web pages often need to wait for all of the necessary resources to be downloaded in order to start rendering the page. Unless browsers start with an especially slow connection, even doubling the speed will not make much difference. But with growth in latency, load times increase linearly. One core way to reduce this load time is to use a CDN to strategically move the content closer to the user.
With a traditional content distribution network, when an application is deployed, the application code and media resources are pushed out to one or more origin servers. These two types of services have traditionally required separate servers. But with Amazon CloudFront, it's now possible to push all the code to one place and let the service manage the whole content optimization process.
After the data has been pushed out to the origin server, the CDN adds or changes data stored in caches on servers that are distributed on the network. This back-end distribution network can be more efficient than going straight to the user because the owner has more control over the applications running on both servers.
One of the biggest problems in making CDNs work smoothly lies in managing caches that receive data from the origin server. The CDN network has to invalidate the caches stored throughout the network and distribute the new data. The more automated this process is, the less time an IT team will spend working on it.
Improving the app code
There are challenges in doing this well. Rewriting the HTML can break the page, said Rayburn. Optimizing once per page is not enough. The best results depend on the particular browser and device. But optimizing for performance at the development level can require significant development resources to implement -- not to mention, maintenance can be a problem. In order to reduce the amount of IT staff time spent on optimization, consider using tools to automate the implementation of these techniques.
The largest CDN providers are starting to integrate dynamic site acceleration capabilities into their CDNs. These include Limelight Networks, Akamai and CDNetworks. In addition, Amazon is now bundling basic DSA capabilities into CloudFront at no additional cost.
Podjarny said that FEO tools can also apply optimization at the network protocol. This would mean adjusting TCP windows and incorporating forward error correction to reduce the need to resend lost packets. When these techniques are combined, the difference can be dramatic. Podjarny said that in a high-latency environment, they can reduce the start time by four times and cut load time in half.
A side benefit of CDN infrastructures is that they help create a buffer to protect the enterprise against distributed denial of service (DDoS) attacks, which are growing in both frequency and intensity. Their substantial bandwidth can reduce the outages and performance degradations caused by these types of attacks.
In order to address this trend, many CDN vendors have developed specialized DDoS security services that operate alongside content distribution scalability and dynamic site acceleration techniques. Leading cloud providers in this area include
Leveraging the masses
Emerging peer-to-peer (P2P) CDN technology promises to turn users into servers for storing and sharing content. The fundamental idea is to shift the bandwidth required for distributing content from the backbone CDN infrastructure to the underused uplink capabilities on end-user computers. This kind of capability has traditionally required dedicated software like BitTorrent and has had challenges in protecting content.
The recent addition of WebRTC support in modern browsers is likely to usher in the use of P2P to complement CDN, said Dean Bubley, founder of Disruptive Analysis, which does market research on this field. This approach makes it easier to set up users as P2P nodes without having to install dedicated software on each client. P2P services bolt onto existing CDN or cloud networks and could reduce CDN service usage by 90% for some types of content.
The limitations of P2P for CDN are that the technology is relatively immature and there are fewer tools for digital rights management (DRM), reporting and management. As these kinds of capabilities improve, P2P-based services will make sense for several use cases such as video, application and software update distribution.
Companies working on these P2P bolt-ons for enterprise applications include Viblast, Peer5, Steamroot, and Swarmify. In addition, a number of CDN and cloud providers have been snapping up P2P software startups, which could bolster their existing service portfolio. Akamai acquired Red Swoosh, Microsoft acquired Pando Networks, and Yahoo acquired PeerCDN. New services built on this capability could help complement the rest of their CDN ecosystems.
Scaling ISPs and carrier networks
One of the challenges of both traditional and P2P CDN networks is that both techniques require additional bandwidth from Internet service providers (ISP). Multicast distribution protocols could, in the long run, allow for much better scalability of broadcast video over the Internet. They would also introduce less overhead on the ISP network. These capabilities are built into modern routers, but are often not turned on for a variety of reasons.
New IPTV broadcast services built on top of multicast, such as Octoshape Infinite HD-M technology, use forward error correction techniques to make video distribution techniques more practical and seamless. The service passes these bandwidth savings to content providers by only charging a fee based on a per-channel price, which can be preferable to bandwidth-based pricing that grows with the number of users.
Read part 2 of this CDN series
CDNs are helping to drive an explosion of traffic on carrier networks by optimizing the backbone. But the transmission path over the last mile of the network is far from optimized. Network operators are looking at tools to reduce the Opex and Capex.
Carriers are also starting to deploy transparent caches that reduce the impact of video broadcasts on their services. One of the biggest challenges is deploying the caches in a way that respects the business logic and licensing models of content owners. New transparent cache technology from companies like Qwilt enables carriers to buffer this content so it respects the DRM and the business rules of content owners.
In this model, video delivery platforms would become part of the ISP infrastructure and would be managed in the way routing is managed today. Dan Sahar, co-founder of Qwilt, explained, "Video delivery nodes would interface back into the commercial CDN infrastructure, enabling the CDNs to extend their serving capacity at close proximity to subscribers' locations. This integrated approach would also complete the feedback and reporting loop for all parties in the video delivery value chain."
CDNs and their associated ecosystems give the enterprise many options for improving the user experience while reducing costs. In order to get the most benefit, enterprise architects need to consider traditional CDN approaches as well as the new types of distribution technologies like P2P-CDN and multicast. These could either complement or replace existing CDN services.