PCFormat Forum Archive

Hi Guys and gals

Can someone please give me a quick lecture (in pcf language ) on SDSL?

Has anyone been using Telcum's new uncapped ADSL?

http://en.wikipedia.org/wiki/Symmetric_ ... riber_line

1) In the wider sense it is a collection of Internet access technologies based on DSL that offer symmetric bandwidth upstream and downstream. It is considered the opposite of asymmetric digital subscriber line (ADSL) technologies where the upstream bandwidth is lower than the downstream bandwidth.
2) In the narrow sense SDSL is a particular DSL variant that supports data only on a single line and does not support analog calls.

So it does not support voice but up and downstream has the same bandwidth. On a 4Mb ADSL you have a 3.5Mb Down and 512kb Up stream data connection and you can still make phone calls while transferring data. ADSL has a steep contention ratio as a rule where SDSL does not. It could be that Telescum does employ the same contention ratios but I highly doubt it

wait...

Is telscum's uncapped SDSL?

or am i just reading this wrong?

Does any ISP offer SDSL? dam i would love that.. never use my telkom line for calls anyway...

DeathStrike wrote:wait...

Is telscum's uncapped SDSL?

or am i just reading this wrong?

Does any ISP offer SDSL? dam i would love that.. never use my telkom line for calls anyway...

There are people that do offer it but it is a very selected few and not all over the country either. Dunno why as it is actually cheaper to roll out.

..But you pay through your nose for it.

That's been around for ages in the rest of the world....

It's called NDSL or Naked DSL here.

You buy a line with no analogue service and most people just get a VOIP service to go with it - if they get a phone at all.
Actually works out cheaper here.

Is naked DSL synchronous though?

KALSTER wrote:Is naked DSL synchronous though?

No, but then neither is SDSL - the S stand for Symmetrical

It's basically where they use your whole twisted copper pairs frequency range for data only, so you cant get voice over it. With this extra bit of space on the line for data they can send and receive data at lower speeds at the same time, making it for all intents and purposes synchronous.

Naked uses the usual DSL range of your copper and just doesn't make use of the voice range, and doesn't charge you for voice.

It's worth noting that SDSL still cant overcome the upload threshold of DSL, so it it will never be faster than 2Mbps both ways...
And knowing Telkom they will give you a pipe ridiculously slower than that.

The only benefit with it is that because it's a smaller pipe than traditional DSL there is less contention, so users on an SDSL network can get pretty close to the advertised speed all the time - even when others are using it consistently, making it attractive to businesses.

The ISP I work for in Aus offers it, it's called SHDSL here http://www.iinet.net.au/business/shdsl/overview.html

We also have something called Bonded DSL. Where you basilcally pay for 2 DSL lines and they bridge your 2 ports on the exchange effectively doubling your speed.

jamin_za wrote:

KALSTER wrote:We also have something called Bonded DSL. Where you basilcally pay for 2 DSL lines and they bridge your 2 ports on the exchange effectively doubling your speed.

Yeah my work has this... currently using two bonded 10Mbps lines and a wireless direct link to our servers... which means even if the adsl goes down we can still access our servers.

No, but then neither is SDSL - the S stand for Symmetrical

Damn, that's what I meant.

It's worth noting that SDSL still cant overcome the upload threshold of DSL, so it it will never be faster than 2Mbps both ways...
And knowing Telkom they will give you a pipe ridiculously slower than that.

But why though? Is it a hardware limitation at the user side?

KALSTER wrote:

No, but then neither is SDSL - the S stand for Symmetrical

Damn, that's what I meant.

It's worth noting that SDSL still cant overcome the upload threshold of DSL, so it it will never be faster than 2Mbps both ways...
And knowing Telkom they will give you a pipe ridiculously slower than that.

But why though? Is it a hardware limitation at the user side?

Nope... it is a situation of being able to send in one direction at a time. Remember that the single channel is used for both up and down.

The slow upload capability of all DSL lines is a hardware limitation that wont be overcome until we all have exchanges in our homes

SDSL does not in fact overcome this at all. It cheats and caps the download speed at the same as the upload speed - effectively if you use SDSL, you download slower than you would on ADSL.

To answer jee a bit more:

While this might not sound ideal, consider being a business and needing to send as much data as you receive.
Your Telkom Business ADSL line can do 4mb down, but only 512K up... But you don't see anything near that in the real world due to contention etc.
Wouldnt it be better to have a 1mb line going both ways Many businesses in this position would prefer that.

And as I have also mentioned, SDSL needs it's own dedicated network since it's a slightly different implementation of the DSL standard and doesnt play nicely with ADSL. That means your line runs on a network with far fewer users than standard ADSL, and the fact that everyone on it connects at lower speeds further lessons the strain on the network made by bandwidth hogs and leeches. Meaning that you can pretty much be sure you will be getting as close to the maximum line speed advertised for the service as your physical setup allows.

Make sense

ta jamin

Thanks for the info hamin. Was a good read .

Good on 'ye mate.