Why is there a difference between up and down link stats?

[DJ...]

As per the title, why would there be significant differences between my upload speed and my download speed based on the router information? Is this purely because uploads sync at lower speeds or is there something more to it? As an example, my upload attenuation is nearly half what my download attenuation is and the SNR margins are about 30% better. I keep wondering why, and the first thing that strikes me is the lower speed in comparison to downlink sync speed, but surely there is more to it than that? Or is it the same line as the downlink just at lower speeds?

 

[chrisc]

Its just a way of managing the available bandwidth. Downloads are far more important to you than uploads, which are just used to confirm receipt of information packets or to transmit email

 

[DJ...]

Its just a way of managing the available bandwidth. Downloads are far more important to you than uploads, which are just used to confirm receipt of information packets or to transmit email

I think you misunderstand. I'm not asking why they're different speeds. I'm asking why my router reports different stats for the two. Such as SNR and attenuation. Is it simply the lower sync speed?

 

[chrisc]

Oh, I am sorry. My router only shows me stats for the download speed, so I cannot offer an answer

 

[Unhappy438]

Its due to the frequency, upload has a lower frequency than download.

 

[Tim the Techxpert]

Hi there i agree with Unhappy438 Frequency is the reason.

Regards

Tim

 

[DJ...]

Can you guys explain the frequency a little better to me, a layman?

 

[T-Man]

It's all in the name.

Asymmetric digital subscriber line (ADSL) - meaning up will be (s)lower than down.

ADSL is intended for more downloads than uploads.

 

[qinglung]

Too lazy to try and explain

But read this: Attenuation Dwn/Up quite different. Previous posters alluded to this.

 

[Dan C]

Basically your DSLAM transmits at a better rate (signal, download) than your modem does back to the DSLAM (upload)....

And that's my theory and sticking to it

 

[grim]

Here you go:

There are both technical and marketing reasons why ADSL is in many places the most common type offered to home users. On the technical side, there is likely to be more crosstalk from other circuits at the DSLAM end (where the wires from many local loops are close to each other) than at the customer premises. Thus the upload signal is weakest at the noisiest part of the local loop, while the download signal is strongest at the noisiest part of the local loop. It therefore makes technical sense to have the DSLAM transmit at a higher bit rate than does the modem on the customer end. Since the typical home user in fact does prefer a higher download speed, the telephone companies chose to make a virtue out of necessity, hence ADSL.

Sauce: http://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_line

 

[ponder]

But read this: Attenuation Dwn/Up quite different. Previous posters alluded to this.

Attenuation is a function of frequency, your upstream falls in a lower frequency range thus the attenuation is lower, I'll try to elaborate more tomorrow (i'm rusty).

 

[ponder]

This is a pretty good explanation, http://www.westernextralite.com/resources.asp?key=45

Copper Wire and Its Limitations

Due to the electrical properties of copper wiring, data signals will undergo some corruption during their travels. Signal corruption within certain limits is acceptable, but if the electrical properties of the cable will cause serious distortion of the signal, that cable must be replaced or repaired.

As a signal propagates down a length of cable, it loses some of its energy. So, a signal that starts out with a certain input voltage, will arrive at the load with a reduced voltage level. The amount of signal loss is known as attenuation, which is measured in decibels, or dB. If the voltage drops too much, the signal may no longer be useful.

Attenuation has a direct relationship with frequency and cable length. The higher the frequency used by the network, the greater the attenuation. Also, the longer the cable, the more energy a signal loses by the time it reaches the load.

A signal losses energy during its travel because of electrical properties at work in the cable. For example, every conductor offers some dc resistance to a current (sometimes called copper losses). The longer the cable, the more resistance it offers.

Resistance reduces the amount of signal passing through the wires - it does not alter the signal. Reactance, inductive or capacitive, distorts the signal.

The two concerns of signal transmission are:

That enough signal gets through. (Quantity)
That the signal is not distorted. (Quality)

If you look at my previous post wrt frequency and that little diagram you can 'see' how the above applies.

 

[HavocXphere]

@DJ I think this is the wrong battle to be fighting. The average user will be uploading a little bit an downloading a ton of stuff. Thats the way it is. Naturally ISPs & Telkom will respond to this by offering packages favouring download.

 

[ponder]

When you say

and the SNR margins are about 30% better

what do you actually mean, the upstream SNR values are lower or higher than the downstream?

 

[DJ...]

@DJ I think this is the wrong battle to be fighting. The average user will be uploading a little bit an downloading a ton of stuff. Thats the way it is. Naturally ISPs & Telkom will respond to this by offering packages favouring download.

Not fighting anything. I was really just trying to get a grasp of what it means...

 

[DJ...]

When you say



what do you actually mean, the upstream SNR values are lower or higher than the downstream?

The upload SNR margins are better than the download...

 

[w1z4rd]

They do it so you cant host services on the adsl network and you are forced to pay for more expensive diginet lines to host.

 

[MickeyD]

@DJ... check your email...

 

[Seriously]

They do it so you cant host services on the adsl network and you are forced to pay for more expensive diginet lines to host.

Ditto. It's a telscum control feature. If your upload speed would be the same as the download speed then your potential bandwidth increase dramatically. Years ago my satellite link downloads was so so due to the fact that my upload speed was limited to telephone dial up speeds but when I got ADSL it made a higher upload speed possible and as such my download speed more than doubled.