Hi KB.
"They can turn up the port but they can't make sure you get that."
That is the common perception, but it's not always true. It's true for consumer grades of service, where most providers do not adequately provision their upstreams (and consequently, their port sizing on DSLAMs, as well) for optimum performance, once there is a significant level of usage on the system. They don't issue guarantees on consumer grades of DSL, to net it out. Instead, they leave a lot to chance, and bump up their back end capacity just ever so slightly to stay ahead of alternative access methods, assuming that there is a race taking place in a locale. If not, languish.
In this sense, the cablecos and the ILECs will play a kind of chicken with each other in the future. Each will test the endurance and the patience (and you can forget about stickiness here, if users are fed up with wait times, they'll jump) of their own subscribers, trusting that if they keep the level of service just a little better than totally horrible during peak hours, then their subs wont jump over to the other side.
We'll have to wait and see just how accurate this prediction is. It will call for some broadband video applications to become popular first, like the ENRON/Blockbuster deal, before we can truly know how well the providers will respond in the future.
Of course, if they stick users with $95/mo minimums because they use their service to access corporate servers (even if only occasionally), then this is another way to keep congestion down and throughput levels up, as we stated upstream. But where does the promise of broadband Internet go, if this is the case? Must users subscribe to three levels of service? One for the kids, one for the VPN or business, and one for the adult once business is finished for the day?
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If you examine the service levels available from some of the commercial grade dsl's, they actually "do" offer a guaranteed rate that is sustainable, along with other features, such as tunneling and various levels of security, which businesses demand. But all of this comes at a price, and usually requires that you subscribe to one of their symmetrical services, such as HDSL or SDSL.
In the ATM world, which is what most carrier-grade DSL providers use as their undercarriage, it's possible to set QoS (although, frankly, I don't know about this, and just how commonplace QoS actually is) and even provide you with a constant bit rate service (or circuit emulation at the T1 rate), if that is what you want. In the latter case, however, HDSL or SDSL would be required, not ADSL.
Similar levels can be achieved, but not guaranteed, using IP over Ethernet (another, less-popular form of DSL), provided that contention issues are taken into account and resources are allocated accordingly, in the overall system design. But don't hold your breath on guarantees here, either.
On cable, I believe that COM21's ATM over Cable for business and telecommuting VPN still makes the same level of guarantee available. Just don't try to put too many telecommutes on the same system using this method all at the same time. And it is possible to offer SLAs here, at the sacrifice of others, who are using the consumer level of cable modem service, of course, and who do not have such guarantees. Instead, they live on leftovers.
But most cable ops do not use ATM, they use a modified form of [queued and windowed] Ethernet, instead. It really does come down to supply and demand, and the bandwidth limitations of the last mile medium. Both its inherent bandwidth characteristics, and the modulated throughput rates and protocols used to deliver payloads. AND, very importantly, the number of users vying for the same slice of bandwidth. HTH.
FAC |
