Cache and carry.

Web switching puts content where users can access it when they want it, every time.

Road Runner, the nation's leading cable modem high-speed Internet provider, wanted its on-line content delivery to be ultrafast--ideally, 50 to 100 times faster than standard dial-in Web connections. To ensure lightning-fast downloads to hundreds of thousands of users at once, Road Runner deployed content-smart Web switches in each of its 21 data centers nationwide.

Content-smart Web switches enable Road Runner to place content within immediate reach of about 500,000 subscribers, on a network with access to 10.4 million homes. Road Runner is using the Web switches in conjunction with Web caches to deliver content up to 100% faster than standard dial-in Web connections. In addition, the Web switches have reduced the need for Road Runner to purchase additional Internet bandwidth by as much as 20%.

Besides reliably delivering and selectively prioritizing and load balancing Road Runner's varied multimedia content, the Web switches enable high-performance caching, permitting the company to push popular on-line content, such as CNBC and CNN news, closer to users. This translates immediately into happier customers who get the online content they want quickly and reliably, without waiting, downtime, or sluggish copper-wire network connections.

Road Runner, a joint venture among affiliates of Time Warner Inc., MediaOne Group, Microsoft Corp., Compaq Corp., and Advance/Newhouse, has exclusive rights to tier-1 cables running past 27 million homes across the U.S. The company also owns and maintains local networks for cable companies from hundreds of smaller data centers. Road Runner supports not just this Internet service but content for it.

One of Road Runner's strategic initiatives is to optimize the delivery of Road Runner content by placing that particular content as close to users as possible, cutting down on transport costs and providing better, faster service to customers. The Web switches' intelligence enables them to direct only requests for Road Runner/Time Warner content to local caches, bypassing the cache for non-cacheable Road Runner/ Time Warner content and all other requests, routing them directly on to the Web for content.

Road Runner needed a next-generation Web switch that would direct Web traffic based on identifying individual users and routing it to the best server available for the specific content requested. Traditional "Layer 4" switches make load-balancing decisions based on TCP (transfer control protocol) port 80, offering no glimpse into what content is being requested, other than that it is HTTP. Because they can see beyond the IP layer to the URL and cookie that identify users, Web switches can intelligently direct specific content requests to the local caches, so users receive information far more rapidly. Alternately, Web switches can route requests directly to the Web for dynamic content, such as CGI or ASP, that can't be cached.

"Content is closer so it gets to the user reliably, and the performance is outstanding," says Stephen Van Beaver, Road Runner's senior vice president of operations. "We consider the ability to move content closer to users a major competitive advantage. Another benefit is that operational costs of the Web switch are very low. It's a self-contained unit that doesn't require a lot of handling or care."

DELIVERING ON THE PROMISE OF BROADBAND

To meet growing demands for bandwidth, reliability, and speed on the Web, Internet service providers, as well as broadband backbone and infrastructure providers, are spending billions of dollars for more bandwidth. Internet backbone congestion and latency have prevented broadband access technologies, like cable modems, from functioning at their true potential. Selectively routing requests for popular content to local caches--and avoiding the Web's congestion--delivers faster response times and more satisfied users. Bypassing caches for non-cacheable content relieves the caches from extraneous processing and latency.

Not all Web switches could bring the kind of network intelligence to the table that has enabled Road Runner to maximize the power of cable modems and reliably deliver Web pages to end users at speeds no other broadband provider can match.

"Road Runner considered several switches from competing companies before choosing a solution. We based our choice on the particular Web switch's superior sophistication and rich feature set, including load balancing, content provisioning, dynamic content replication, and diagnostic monitoring," says Van Beaver. "They may look at the packets, but not all Web switches read into them to the same depth. We needed to choose carefully, and there has been a big, big benefit--both through the intelligent caching ability and also redirection of content--in better managing the infrastructure. We've seen a huge improvement to bandwidth, for example, and of course, cost savings."

A MORE INTELLIGENT CACHING MECHANISM

Web switches look deep into the HTTP request headers all the way down to the URL and cookies to determine what content is being requested. Looking at the complete URL--including dynamically generated URLs with strings of more than 256 bytes--is the only reliable method for determining what content a user is requesting. By accessing information at this level, real Web switches can reliably bypass caches for non-cacheable or dynamic content, such as common gateway interface (CGI), active server pages (ASP), or database queries, and transmit these non-cacheable requests directly to the origin server. This dramatically improves Web response times by eliminating the latency caused when caches must repeatedly forward all requests for non-cacheable content to the Internet.

Web switches enable Web administrators to create an unlimited number of content rules that bypass the cache for cacheable content at their behest. Content that Web administrators might deem should be non-cacheable could include, for example, real-time stock quotes or frequently changed Web pages. In contrast, enhanced Layer 4 Ethernet switches route all HTTP requests, including those for dynamic content, to the transparent caches. With this approach, caches incur additional processing overhead when they must forward requests for dynamic content to origin servers, resulting in slower response times for Web users.

"By looking at HTTP and URLs, content-smart Web switches optimize the caching mechanism, but putting policies or rules around content enables tiered services, differentiated routing, and service-level caching," Van Beaver says. "A Web switch that enables service-level caching gives providers preferential treatment for just about any kind of frequently requested content service, be it news, health, or sports--you can get rather specific about how you'd like to optimize the caching mechanism."

"From the user's perspective, we can optimize the content so it aligns with customer segments like sports enthusiasts, hobbyists, or financial content sources," Van Beaver says. "The Web switch can optimize delivery of that specific content by enabling an architecture that keeps that content closer to users. It's not a hollow box. Its power is that it lets you define what you do with the packets it is handling. Ultimately, this enables us to optimize the customer experience."

FUTURE PLANS

Road Runner is using the Web switches as its primary means to distribute content to local caches. But Road Runner is also considering additional Web switches to provision content between servers as well. The newest Web switches have introduced a faster way of bringing together Web content from various servers, splitting and prioritizing high or low priority content, and routing requests to the servers based on the kind of content being requested. Intelligently load balancing HTTP traffic among various servers, caches, and the Web maximizes server capacity and reduces latency, ensuring the network remains fast, reliable, and--in many ways--self-regulating. Road Runner also uses the Web switches for monitoring and diagnostic functions, all from a single easy-to-maintain network device, as opposed to three or four pieces of equipment.

"Our Web switches enable us to provide users with immediate access to content without going on to the Internet," Van Beaver says. "It's local, like having a Web server one town over. Since you don't have to go to the Internet, you don't have to deal with Internet congestion and traffic. For us, the right Web switches were and are a very powerful, strategic tool."

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RELATED ARTICLE: Service-tailored caching

Traditionally, caches were designed to be deployed close to the user to temporarily store copies of any frequently requested content, eliminating the requirement to traverse the path to the origin server for every request. This improved the response time for any frequently requested content and provided better utilization and cost savings for WAN bandwidth.

This approach is economically attractive for international applications, where intercontinental latency is significant and bandwidth is expensive, and for corporate users, who could also use proxy caches to control what content was being requested through the corporate Internet connection.

In North America, where bandwidth is relatively inexpensive and latency is relatively insignificant, there has been little economic incentive to deploy caching technology on a broad scale in the Internet. However, the deployment of broadband access technology, including xDSL and cable modems, has created demand for caching. As bandwidth for the last mile has increased, it has shifted the bottleneck to the next link in the chain, the uplinks to the Internet--from the cable head ends and the xDSL points of presence (POP). Caching can be deployed at these points to equalize the bandwidth mismatch, shifting more traffic on to the last mile, improving user response time, and off-loading the backbone connections to the Internet.

Service-tailored caching provides a broad-based economic incentive by optimizing the delivery and response time for specific content, creating a valuable service for the owner of that content.

For example, if a service provider or cable ISP deploys caching technology at regional aggregation points where large numbers of users connect to the Internet, it can use traditional caching methods to store copies of all frequently requested content. In this case, the service provider bears the entire cost and directly benefits from reducing backbone bandwidth. The users benefit by receiving better overall response time but are unlikely to tolerate any increase in access fees as a result.

If the service provider can deploy the caches with policies to optimize the delivery of specific content, this creates a third constituency: the content owner that has an economic interest in optimizing response time for its content. For example, a national cable ISP can now provision a service that may be attractive to a large content provider. The content provider buys the service from the cable ISP and the caches are configured to store only content belonging to the content provider. The content provider benefits by ensuring that its content is being delivered significantly faster to all of the cable modem users, the ISP still benefits by reducing backbone bandwidth, and the user benefits from better overall response time.

Johnson is director of technical marketing, ArrowPoint Communications, Inc., Westford, Mass.