DSL help plz.

[ME]

On Tue, 28 Dec 1999, Rick Moen wrote:
> Subject: Re: DSL help plz.
> Quoting ME (dugan at libwais.sonoma.edu):
> > Ys this is likely to e the case. A T1 is likely to outperform SDSL when
> > uploads and downloads both approach 1.544Mbps. In today's environments,
> > SDSL works ok for may people running a mostly DL service while a full T1
> > works better to tie together two LANs which are both likely to exchang
> > traffic simultaniously.
> I doubt you have this right.  The "S" stands for "symmetric".

This is not just from me, this is from PacBell and 2 northbay xDSL
providers. Maybe you can ell them they are wrong:

Please check http://public.pacbell.net/faq/dsl_faq.html

"Will business customers want to replace their existing DS-1 (T-1) 
Internet service with DSL? There are clear technological differences
between DSL and T1 Internet service. The first of which is that T1 service
is 1.5Mbps both ways. This is important to many business applications
including the hosting of a Web site. In addition, DS1 is a proven
technology. While our technology tests demonstrate that DSL is very
reliable, businesses tend to rely on established technologies when
business critical data is at stake. The final difference is in regard to
availability. Currently, DS1 Internet service is more widely available
than DSL service. " 

Mention of "both ways" is full duplex. I believe that most xDSL are not
ale to upload and download at max speeds simutaniously.

On the original issue of latency, that does not describe bandwidth, they
are two different animals.

> > Even if it is not true "full duplex", 8 to 9 Mbps is fast enough to
> > simulate a pipe aster than a T1.
> 
> However, I wasn't _speaking_ of 8 - 9 Mbps:  At my building, housing The
> CoffeeNet, my hosts, Richard Couture's, and several of our clients', we
> went directly from T1 service to 1.1 Mbps SDSL, and our connectivity has
> continued to have all the characteristics of full-duplex.

Have you attempted to push 1.1 Mbps transmissions and 1.1 Mbps receiving
on the line at the same time? Many variations of TDM based systems used a
shared bandwidth on the media. ATM at one time claimed gigabit speeds
because 650Mbps at full duplex allows for up to 1.3Gbps on the wire at the
same time, but now the max speeds have changed.

If your xDSL cable provider offers you 2Mbps SDSL, you need clarification:
Does that mean 2Mbps both ways simultaniously, or do they try to market
the SDSL by assuming that 1Mbps UL and 1Mbps DL adds up to 2 Mbps. (There
are telcos that market their speed differently.

This does happen, and will continue to haappen. Check out the purhase of
scanners that claim higher scan rates through software interpolation, or
tape drves that sell with the assumption of 2:1, 3:1, and 4:1 hardware
compression assumed.

Of course i could be mistaken, since I have been wrong before.