Zyxel P-791R v2 [19/98] Dsl faq

P-791R v2 Support Notes

DSL FAQ

1. How does DSL compare to Cable modems?

DSL provides a dedicated service over a single telephone line; cable modems

offer a dedicated service over a shared media. While cable modems have

greater downstream bandwidth capabilities (up to 30 Mbps), that bandwidth is

shared among all users on a line, and will therefore vary, perhaps dramatically,

as more users in a neighborhood get online at the same time. Cable modem

upstream traffic will in many cases be slower than DSL, either because the

particular cable modem is inherently slower, or because of rate reductions

caused by contention for upstream bandwidth slots. The big difference

between DSL and cable modems, however, is the number of lines available to

each. There are no more than 12 million homes passed today that can support

two-way cable modem transmissions, and while the figure also grows steadily,

it will not catch up with telephone lines for many years. Additionally, many of

the older cable networks are not capable of offering a return channel;

consequently, such networks will need significant upgrading before they can

offer high bandwidth services.

2. How do I know the DSL line is up?

You can see the DSL LED on the P-791R v2's front panel is on Green when

the DSL physical layer is up.

3. How does the P-791R v2 work on a noisy DSL?

Depending on the line quality, the P-791R v2 uses "Fall Back" and "Fall

Forward" to automatically adjust the date rate.

4. Does the VC-based multiplexing perform better than the LLC-based

multiplexing?

Though the LLC-based multiplexing can carry multiple protocols over a single

VC, it requires extra header information to identify the protocol being carried

on the virtual circuit (VC). The VC-based multiplexing needs a separate VC for

carrying each protocol but it does not need the extra headers. Therefore, the

VC-based multiplexing is more efficient.

5. How do I know the details of my DSL line statistics?

In WEB Configurator, Maintenance -> Diagnostic -> DSL Line -> DSL Line

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