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Building a better trough

Sat, 09/30/2006 - 8:00pm
Brian Santo, Senior Editor

What's the difference between a bandwidth hog and a great customer? Nothing some additional network resources and an attitude adjustment couldn't fix. Beauty (it says here) is in the eye of the beholder.

'Building A Better Trough'

Three years ago, that kid choking your network with music and movie downloads was a felon. Today, his mom is doing it too, and they're both legit. Today, a good chunk of peer to peer (P2P) traffic is probably at least dicey from a juridical standpoint, but odds are good that whatever it is will be officially sanctioned three years from now.

When you get right down to it, the problem isn't that a small percentage of users consume the vast majority of your capacity, or even the legal status of what they're doing. The problem is that they are a traffic management nightmare–which, when thought of objectively, isn't their problem, is it?

There are all sorts of ways to deal with the gluttons who show up at the all-you-can-eat diner of your Internet access service. And as these tools and techniques are implemented, more and more cable operators are coming around to the view that the people they once considered bandwidth abusers might be better viewed as power users, with the potential to join the ranks of their most lucrative customers.

There are several ways to deal with power users. One is to manage your power users by imposing limits to their access. There are several ways to do that, with diplomatic ramifications that run from lose-lose to win-lose to win-win.

Another is to manage your network better, including the vital resource of bandwidth. It's possible to do so, some operators report, with the cooperation of your power users.

Another approach is to simply shovel more bandwidth out there and hope your power users can't chew and digest it all until you're ready to slop another shovelful at them.

Managing power users

Many have long advocated metering bandwidth consumption and charging for actual usage. Consumers generally hate the idea of being billed per bit, though.

But there are other ways to limit consumption. They include cutting off the service of a subscriber who far exceeds bandwidth limits, reducing bandwidth available to specific subscribers to discourage excessive downloading, trying to up-sell power users to a faster tier with a bigger bandwidth consumption allowance, and charging per bit after a certain allowance is exceeded.

Figure 1
Figure 1: P2P and other bandwidth-intensive applications are driving broadband adoption and service
upgrades, but operators have to provide quality of service for revenue-generating applications like VoIP.

The first two routes are almost guaranteed to alienate customers, but Canadian operators Rogers Cable and Cogeco are finding some success with the latter two courses. Their caps have inspired some subscriber aggravation, but not enough to drop the caps. Both cap monthly bandwidth consumption, and charge for usage over the cap.

Cogeco limits its Lite/Mini tier subscribers to 10 gigabytes a month, its Standard subs to 50 GB a month, and its Pro tier subs to 100 GB a month. The tactic is designed to encourage people who consistently bump up against their limits to migrate to a higher tier.

Rogers puts a 100 GB limit on its top tier, but a 60 GB cap on all lower tiers. Rogers finds the lower tiers are practically self-limiting, in that it's hard to download 60 GB of data in a month at slower speeds.

Rogers not only manages network bandwidth but also monitors it, using the packet inspection technology Cisco Systems Corp. acquired with its purchase of P-Cube two years ago.

Power users represent about three percent of all subscribers. Rogers identifies that sub base sliver, and then calls them to find out what's driving usage. Rogers found not all power users are wittingly such; in some cases, the subscriber's computer was infected with a virus, or they had an open wireless connection that was being

hijacked. Rogers coaches those subs on how to use the security software that comes free with Rogers' service, or to password-protect their system.

Rogers simply asks most of the rest if they'd shift their downloading to off-peak traffic hours–and most comply.

"Heavy users are generally sophisticated users," says Terry Canning, Rogers Cable's VP/GM of Internet services. "They get it. With the caps, we rarely have to do any policing other than contact them."

Usage monitoring and the ability to allocate (and, by extension, limit) bandwidth usage are provided through PacketCable Multimedia (PCMM) technology and the use of policy servers from the likes of Cable Matrix, Camiant Inc., and C-COR Inc., often in combination with deep packet inspection (DPI) systems from companies such as Allot Communications, Ellacoya Networks and Sandvine Inc.

But the peaks on usage charts are getting higher, and the troughs aren't nearly as shallow as they once were. There's simply more traffic on the network, and it's only going to get worse.

Furthermore, the number of those who might qualify as power users is increasing. Rogers Cable discovered that the top three percent of users are not the same subscribers from month to month.

That only means that there are more people apt to use a lot of bandwidth. Today, roughly one in four subscribers are using P2P services, up from perhaps one in 20 in only the past year, according to Paul Kilbank, director of product and solutions marketing at Sandvine.

Music is increasingly a download business. Films make for big fat files, and more and more people will be downloading them and sharing them. The average camera can now take video too, and it's a matter of time before more and more people are making and swapping videos that are hours rather than minutes long. Then throw in the increasing trend of network storage, which will steadily increase traffic on the upstream, too. Subscriber management isn't enough.

Managing bandwidth

Trying to migrate subscribers who download tens of gigabytes of data a month to a higher tier makes sense, but for subscribers who order only the occasional large download (a film or two a month, for example), a higher tier might not be appropriate.

Comcast Corp. has introduced a feature called PowerBoost that takes advantage of the capability to temporarily allocate bandwidth afforded by PCMM. Comcast monitors traffic, and when it detects a qualifying download in progress, it temporarily boosts transmission speeds to that user to up to 12 Mbps–provided the additional bandwidth is available.

Figure 2
Figure 2: In PacketCable Multimedia (PCMM), an application manager (AM) authenticates and
authorizes subscriber use and converts application sessions into resource requests by signaling
to a policy server. The policy server then signals the cable modem termination system (CMTS)
to enforce DOCSIS service flows.
Source: Ellacoya

The increase remains in effect only for the first 10 MB (for the 6 Mbps tier) or 20 MB (for the 8 Mbps tier) of a file download.

The same capability might be used to allocate additional bandwidth for a specific application such as on-line games. That ability could be presented as a free feature, as Comcast offers PowerBoost. It could also be sold as a service.

Another thing to remember is that cable high-speed data is a best-effort service, and that users frequently get bandwidth in excess of the minimum guaranteed rate of the tier to which they've subscribed. So it makes sense to monitor what each subscriber is actually getting and, if it's necessary to make sure other subscribers get sufficient bandwidth, throttle back those receiving in excess of the minimum rate.

The move to all-digital could also help, as the vast swath of spectrum presently allocated for analog TV can be reclaimed and reallocated.

Similarly, moving to switched broadcast could free up spectrum that would otherwise be dedicated entirely to video.

Moving to MPEG-4 compression may help, but any benefits from the better compression rates afforded by MPEG-4 are likely to be canceled out by rising amounts of high-definition content.

Adding bandwidth will help alleviate–perhaps even eliminate–part of the problem, but bandwidth management will always be necessary because some applications, notably voice-over-IP and online games, don't use a lot of bandwidth, but are subject to latency and jitter. It will still be necessary to identify this traffic and allocate resources appropriately, again with PCMM and policy servers working in conjunction with cable modem termination systems.

Adding bandwidth

But the fact is that bandwidth consumption is going up, and will only continue going up. The common prediction is that it will be necessary to be able to simultaneously feed each household enough bandwidth to support at least two HD streams, perhaps another standard definition (SD) stream, Internet access which will have to support streams of IP-based video and music, and voice-over-IP telephony.

"By 2010, you're going to have to be able to provide 25 to 50 megabits per second to each home," says Mark Milinkovich, Cisco Systems' director of service provider solutions marketing. "Each home may consume a terabyte a month of games, movies and other media. Twenty homes will equal the entire Internet backbone of 1995."

Almost every major operator is in the process of splitting nodes, which automatically buys bandwidth. Each operator has a target for how many subscribers per node it hopes to reduce to, ranging anywhere from 150 to 300.

Something to keep an eye on while node splitting is whether you have a cluster of power users on any particular node, and trying to segment them into different nodes if possible, and if necessary.

Modular cable modem termination system technology should become available perhaps as early as next year. M-CMTS takes some of the functionality of the CMTS and invests it in edge QAMs.

"If you can do that, you should be able to deliver significantly more bandwidth at very low cost," says Roger Slyk, marketing manager for BigBand Networks Inc.'s Cuda CMTS line.

Meanwhile, DOCSIS 3.0 is, among other things, concerned with channel bonding–the ability to combine a minimum of four downstreams and upstreams to achieve an aggregate transmission rate far in excess of what can be accomplished through a single DOCSIS 2.0 connection.

Combine M-CMTS with the channel bonding technology of DOCSIS 3.0, and that can help an operator devote more that 100 Mbps per subscriber. M-CMTS can of course be an intermediate step that buys an incremental amount of bandwidth before upgrading CMTS equipment from DOCSIS 2.0 to DOCSIS 3.0.

Another issue particular to cable is that cable plant is asymmetrical, but more and more bandwidth is being used for symmetrical P2P applications like BitTorrent, which puts particular pressure on the upstream, notes Fred Sammartino, vice president of marketing and product management at Ellacoya Networks.

That problem will only get worse with the rising popularity of "place-shifting" devices like the Slingbox and network storage applications. One of the only things an operator can do about it now is what Rogers Cable is already doing: identifying the power users and asking them to please shift to off-peak traffic times, until more bandwidth can be deployed.

Delivering 100 Mbps or better wouldn't eliminate bandwidth hogs, but they should cease to be a concern–let alone a problem–because 100 Mbps is all any individual subscriber could ever hope to use.

That's keeping in mind, of course, that every past prediction about the maximum bandwidth any individual subscriber could possibly consume has proven laughably inadequate.

One other thing: operators will not be the source of all of the vast additional amounts of data being pumped through their own networks. That means operators will have to pay attention to data distribution at the edge and, especially as they increasingly consolidate on superheadends. Edge routing and switching equipment is being provided by any number of companies, including but certainly not limited to Cisco, Juniper, Lucent, Nortel, and Siemens.

Conclusion

There is, in fact, a race to provide more bandwidth, which allows a provider to offer more services, especially with competition from the phone and satellite companies. But every single person interviewed for this article insisted that the issue is not just about bandwidth; it's about providing a good customer experience.

The key to that is making sure the appropriate network resources for any given application are ready and available–identify, categorize and prioritize.

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