CDN Interconnection: Cost-Effective Alternative to Traditional Peering, Transit On the Horizon, CDNs Say

CDNs were developed as a solution for reducing content-transport costs and improving quality of content delivery, and as over-the-top video and other traffic demands increase, the use of CDNs has spread, said CEO Craig Labovitz of cloud-computing firm DeepField. As of about three months ago, over 50 percent of Internet traffic was served via CDNs, he said. In addition to third-party CDNs like Akamai, Limelight and EdgeCast, content providers and service providers have developed and deployed their own CDNs to take advantage of reduced transit, peering and core network loads, said Labovitz and other industry officials. The market for CDN services was worth about $3.6 billion in 2012, said BCC Research (http://bit.ly/16qTgvc).

Several industry officials told us CDNs are a partial solution to what some in the industry say is increasing contentiousness in peering relationships. CDNs can reduce transit and peering costs by reducing network loads, and they in turn help alleviate the tension that arises when traffic is asymmetrical, they said. “It’s not like we've sat here saying this is a big problem and we don’t have any solutions,” said Mark Taylor, Level 3 vice president-media and Internet Protocol services. “We can put devices or caches inside other people’s networks to originate that traffic much closer to their eyeballs, so it doesn’t have to be carried as far over their network. Or if that last-mile network has a CDN, we can interconnect our CDN with their CDN, so again, our content gets originated much closer to the last mile.” Content providers and those that host their content can find a way to measure the burden on each network, and look for mechanisms like CDNs to keep it in balance as things change, said Taylor. Cogent CEO Dave Schaeffer also said CDNs can help balance unbalanced loads, up to a point. “CDNs have a place in this ecosystem, but they are not a substitute for transit, and they can never put enough boxes in enough locations” to solve this problem, he said.

Each CDN has its own set of standards for routing, capacity and administration, and ISPs have varying relationships with specific CDN providers, industry officials said. Content providers can’t rely on just one CDN to deliver their content, and ISPs can’t rely on just one CDN to improve quality of service on their network, said Chris Osika, Cisco senior director-U.S. Service Provider Practice. He worked with Cisco’s Internet Business Solutions Group to test the possibility of CDN federations. To ensure fast delivery of their content, content providers might have to negotiate thousands of contracts with various CDN companies or service providers, and vice versa, Osika said. Service providers, too, have to negotiate with multitudes of popular content providers to maximize the value of their CDNs to end-users, he said. “[If I'm an ISP], I can’t just create my CDN and start transparently caching Netflix content just because I want to optimize my network.”

To facilitate more streamlined relationships among ISPs and CDNs, global stakeholders have worked with the Internet Engineering Task Force to develop standardized protocols for CDN connectivity, according to the website of an IETF working group on the topic that formed in 2011. It said service providers could then deploy just one CDN cache or box, to which any CDNs could connect. ISPs wanted to ensure they didn’t “get locked into a single vendor strategy when they're deploying equipment into their network,” said Frank Childs, director-product marketing for Akamai’s Carrier Business Unit. Interconnection can give content providers better control over their content distribution, Osika said.

Interconnection could also greatly increase the potential reach of any existing CDNs, said EdgeCast Vice President-Product Management Ted Middleton. “All of us, as CDN operators, look to provide the biggest, the best overall footprint for our customers. We want to enable operators to include content delivery in their network buildouts, because that’s increasingly a viable and cost efficient way to build out capacity,” he said. “Making CDN[s] more ubiquitous and more a part of the fabric of the Internet is obviously a good thing for all parties, at this point.” It’s also more cost-effective, said Jon Alexander, Level 3 director-product management, in a May blog post (http://bit.ly/174tajK). CDN interconnection “can facilitate a more efficient interconnection between two network providers while rewarding both parties for the benefits that they provide to each other,” he said.

Childs said the protocol the IETF group is developing “shows promise,” but has a long way to go. “If there’s an economic incentive to use a device like that, we would certainly consider it. The challenge has been that it doesn’t support most of our customers and everything they want to do, which is more than bit delivery,” he said. Customers also want secure transaction capability, content freshness controls and other customizations, he said. “It’s hard to get to a set of features that’s going to satisfy Akamai, EdgeCast, Limelight and Google, because they're all trying to innovate around their delivery. The standard has to be the least common denominator, so it becomes harder to utilize."

The “lowest-common-denominator” problem made Middleton question whether CDNs or ISPs would adopt an agreed-upon technological standard. “People like an EdgeCast, or an Akamai, have spent literally decades building technology that has a lot of specific application integration capabilities.” Some of those features wouldn’t “make it into a specification that’s general-purpose enough to promote interoperability,” he said. “Do vendors want to spend a lot of time essentially enabling a competitive landscape with a features set that isn’t going to let them put their best foot forward,” asked Middleton. Osika agreed that the business model was the sticking point. “We really discovered you've got to almost strike a bunch of bilateral agreements with every permutation of the members,” he said. “It’s so complex that you wonder whether it’s going to pan out."

The IETF’s interconnection protocol could become another very basic part of general network infrastructure, the same way routers and switches are accepted pieces of any network, Middleton said. “There might be kind of a tiered CDN fabric out there. You might have a set of CDN-like infrastructure that does some basic caching and content localization, traffic routing, request routing, content freshness control, all those kinds of things,” he said. Having “that kind of capability in the network fabric is still a benefit, but I think that will be a different level of service and functionality than what [the] CDN service provider community has operated” to this point, he said.

But CDNs haven’t given up on the idea. Some are discussing virtual servers within a consumer network that could run any CDN’s specific software, Childs said. “Rather than putting it in a cache, or an appliance, I'm going to put in a virtual machine or virtual server that anyone can use,” he said. “That way you can innovate around it, because its your software,” he said. “It’s a relatively new competing alternative to” interconnection, he said. Middleton said the virtual interconnection could still give CDN providers pause, since few would jump at the idea of a single server running their complex software alongside a competitors’ -- though he said he doesn’t “rule out that kind of possibility.”

EdgeCast has also worked to develop its own CDN interconnection, among enterprises that license its software, Middleton said. He said the company lets networks that want to manage and operate their own CDNs license EdgeCast software to do so, and for the last year and a half, EdgeCast has offered a “marketplace environment” wherein those CDNs can interconnect and negotiate arrangements for trading traffic. It gives those networks a bigger global footprint, and allows for easier sharing of content across devices -- a “mutually beneficial type of arrangement,” said Middleton.

EdgeCast isn’t the only company to try to solve the CDN interconnection issue without waiting for the entire industry to coalesce around a broadly accepted protocol. Transparent caching company PeerApp put forth its own solution in May, which it calls the Content Service Extension Initiative (WID May 21 p6). The company, which traditionally sells its caching services to consumer broadband networks, will offer ISPs a new appliance over which any partnering CDN can deliver its content, said Charlie Baker, director-product management. EdgeCast and Limelight have both agreed to participate in the program, he said. Middleton called it “the first tightly integrated attempt” at such an arrangement. “We've collaborated on a set of data and standards that’s going to get exchanged, we've kind of co-developed some technology on either end, and we're coming out with something that we can really and truly claim these are explicitly designed to work together,” he said. CDNs and content providers benefit from extended reach into the network, and also from increased visibility into how their content is consumed, said Middleton. “We can also get metrics and statistics from those caches that allow us to send a more holistic view back to the content publisher.” Because the usage details are captured in a transparent cache, “we can add that back into the metrics we report back to the content publisher, so they maintain visibility into the ways their content is being consumed,” said Middleton.

Through PeerApp’s initiative, ISPs get CDN content without having to choose between placing an EdgeCast or a Limelight box in their network, Baker said. “It provides another way in which traditional CDNs and that lower-level caching fabric can collaborate together, and take advantage of each other’s services,” Middleton said. Childs agreed, but said such a partnership has “the same challenges” as the IETF’s CDN interconnection protocol.