They might be doomed to technological obsolescence, but they'll be bought out before that happens. You're a veteran on this thread. Surely you know how critical the local cache is to robust high speed delivery. This article is a little dated and they do things a bit differently now. Notice Sprint? Why is Sprint going to throw rocks at ATHM? Oh, T. Notice my bolding of "intranet". ATHM's network is private. Bye, bye, FCC.
The Cable Guy Milo Medin built the @Home Network with one basic rule:
Never send the same data twice.
By Todd Spangler
When Milo Medin first heard the plans to build the @Home Network, he said there was absolutely no way it would work. He eventually proved himself wrong after accepting the challenge to build the service's high-speed nationwide network himself from the ground up.
Medin first heard about the plans for the @Home Network in February 1995 from venture capitalist John Doerr. At the time, Medin was a project manager at NASA's Ames Research Center, where he built the space agency's worldwide communications network and was responsible for NASA's Internet program. Doerr was trying to lure him to @Home to build its infrastructure; Medin, however, liked his job and wasn't looking for a new one.
The @Home plan was to offer high-speed Internet connections on the order of 10 Mbps using networking devices running over existing hybrid fiber-coaxial (HFC) cable networks instead of constricted 28.8-Kbps modems, explained Doerr, a partner at Kleiner Perkins Caufield & Byers, the firm that financed @Home along with Tele-Communications Inc. (TCI), Comcast Corp., and other cable operators.
Medin asked how many homes @Home was expected to eventually reach. "About 80 million," replied Doerr.
"I said, 'Let's assume 10 percent of those people sign up. Eight million times 10 megabits per second--there's not enough bandwidth in Christendom to run that system,'" Medin recalled saying.
The financiers were disappointed. But Medin--who describes himself as "a farm boy from Fresno"--began thinking of a way to make it work. The service would have to be engineered around its own private high-speed backbone network, he figured, and Internet content would have to be replicated geographically. It would be expensive, but it would be possible.
Medin decided to seize the chance to put that network in place in June 1995, and as the vice president of networks for @Home Network he now oversees the maturation of his grand experiment.
@Home is now close to hitting the mass-market numbers its investors had imagined. Recently, the company announced a partnership with Cablevision that allows the service to access an additional 5.5 million homes. All told, @Home will be able to provide service to more than 50 million homes in the United States through its partnerships.
That said, though, @Home currently only serves a little more than 12,000 customers. Medin said the current infrastructure can handle up to 180,000 customers, and the infrastructure is constantly being upgraded to reach that multi-million-customer goal.
The expansion plans are all part of the basic architecture he originally developed, which he said is a variation of a combat principle of Gen. George Patton: Never pay for the same ground twice. Medin's corollary to Patton's dictum is "Don't move the same data twice."
To do that, he said, "We had to move the data closer to the subscribers, using multicast and distributed servers."
As a result, @Home implemented the first multicast-enabled network in existence. The service uses a special version of Netscape Navigator that can send and receive multicast traffic, and this summer @Home began a test streaming-media service using Real Networks' RealPlayer to deliver music videos and movie trailers.
"If you're serious about dealing with millions of users, literally every bit of data counts," Medin said. "It's an issue of scalability."
To handle the content distribution, Medin talked to Netscape--another one-time startup backed by Kleiner Perkins--which was just beginning development of its proxy server. The @Home Network still uses a modified version of the Netscape Proxy Server.
At every one of @Home's 55 cable head-end locations, Medin put in two Silicon Graphics Origin200 servers with 10 Gbytes of disk space each to cache content locally. The custom Netscape Navigator client that @Home uses includes JavaScript code that tells the browser which proxy server to query using a simple but effective technique: If the URL has an even number of characters, the browser points to server No. 1. If the URL has an odd number of characters, it goes to No. 2.
For non-Web services such as e-mail, network management, and DNS servers, Medin wanted high-availability systems. At each of the 15 regional data centers, @Home runs two Sun Ultra Enterprise 4000 servers that share a disk array. If one of the servers fails, the other picks up the entire load, which has allowed the network to run with very high uptime rates, Medin said.
The backbone itself, which was actually the last of the network elements that Medin put in place, connects 15 regional data centers over Sprint's ATM service, running at OC-3 speeds (155 Mbps), and connects to the Internet's major network access points. The @Home Network uses Cisco 7500 and 7200 routers and interconnects its servers using high-performance Cisco Catalyst 5000-series switches.
Thanks to the caching and IP multicast techniques, the service's backbone runs very efficiently. Medin said it's almost never more than 5 percent utilized--a low figure that any network administrator would envy.
But because the system is highly distributed, it was very important that all the servers be remotely manageable, even down to being able to dial in via modem and reboot the server, Medin said. @Home has only 10 people responsible for taking care of the servers; another 14 technicians who rotate in three shifts staff the 24-hour network operations center.
@Home uses Tivoli's software to automate network management in combination with some homegrown code. The management software lets Medin and his staff push out operating system patches and software updates. "It's really important, because the network has to be low-cost to maintain," Medin said.
"If you're going to do hundreds of machines, you have to have some way to automate upgrades."
The cable-modem provisioning service, based on an Oracle database, is also fully automated. When a new subscriber is entered into the system, it automatically builds an e- mail account, assigns an IP address, adds a DNS entry, and turns on the cable modem connection at the head-end.
The outlook for @Home as well as cable modem technology in general looks good. Microsoft in June announced a major investment in Comcast, one of @Home's investors. Cisco and three consumer electronics vendors recently announced support for a cable modem networking standard, promising more vendors producing equipment with greater functionality.
"We've entered a new phase in the industry where we're not worried about making the technology work. We're concerned now with making it scalable and reliable," Medin said. Medin said he feels he's made all the right calls in building the network. It was more work than he thought, and he said he would have liked to have chosen his infrastructure vendors more quickly.
But above all, he said, he understood the need for caution and careful planning. "You have a blank sheet of paper only once," he said. "You write on it only once--then, it's a legacy."
And,
Cable Internet Service Delivery
To get into the high-speed Internet services business, cable operators must do more than simply install cable modem gear. Rather, they must build a sophisticated end-to-end IP networking infrastructure in each community they serve that is robust enough to support tens of thousands of data subscribers. That includes items like Internet backbone connectivity, routers, servers, network management tools, as well as security and billing systems. In essence, cable operators are faced with the task of building some of the world's largest "intranets," a serious engineering and operations challenge.
Cable operators are focused on providing high-speed intranet access instead of straight Internet access for a simple reason: a network connection is only as fast as its slowest link. Clearly, the benefit of a 1-Mbps cable link is lost if a subscriber tries to access content stored on a Web server that is connected to the Internet though a 56-Kbps line. The solution to this dilemma is to push content closer to the subscriber, ideally right down to cable headend. This is done by "caching" or storing copies of popular Internet content on local servers, so when a cable modem subscriber goes to access a Web page, he or she will be routed to the server in the headend at top-speed, rather than being required to voyage out onto the congested Internet.
A number of companies are offering comprehensive networking and systems integration services to cable operators entering the high-speed Internet business.
AtHome Corp., which is jointly owned by cable operators Tele-Communications Inc., Cox Communications Inc., Comcast Corp., Rogers Cablesystems Ltd., and Shaw Communications Inc., as well as venture capital firm Kleiner Perkins Caulfield & Byers, has built a high-speed data backbone and caching infrastructure to distribute broadband Internet services through affiliate cable systems.
The Road Runner Group, a joint venture between Time Inc. and Time Warner, has developed a broadband Internet service called Road Runner for deployment by Time Warner Cable systems and those of other MSOs. Additionally, traditional systems integrators such as Digital Equipment Corp., Hewlett-Packard Co., IBM, and Toshiba America Inc. are offering Internet solutions to cable operators.
Shared Network Platform Performance
Most cable modem systems rely on a shared access platform, much like an office LAN. Becuase cable modem subscribers share available bandwidth during their sessions, there are concerns that cable modem users will see poor performance as the number of subscribers increases on the network. Common sense dictates that 200 cable data subscribers sharing a 27-Mbps connection would each get only about 135 Kbps of throughput -- virtually the same speed as a 128-Kbps ISDN connection -- right? Not necessarily.
Unlike circuit-switched telephone networks where a caller is allocated a dedicated connection, cable modem users do not occupy a fixed amount of bandwidth during their online session. Instead, they share the network with other active users and use the network's resources only when they actually send or receive data in quick bursts. So instead of 200 cable online users each being allocated 150 Kbps, they are able to grab all the bandwidth available during the millisecond they need to download their data packets -- up to many megabits per second.
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