DSL speed for dial-up

[WoodrowJWeen]

I've seen several companies advertising DSL speed for dial-up internet connections at prices somewhere between the two. Some indicate that a special modem is required (Joi) and some use only some software (Proxyconn). As an electrical engineer I've been asked if these are legit. I suspect these may be just "snake oil". Does anyone have any experience with either of these services?

 

[JohnFortier]

I would strongly suspect an infusion of snake oil.

The maximum amount of data you can send over a band limited, noisy medium is defined by Claud Shannon's equation and, for a dial up line, a 56K modem is really pushing that limit.

Dial up lines are band limited since they are designed only for voice and the telephone switch can only manage so much bandwidth per connected line. I would look into their claims very carefully, find out from your local LEC what their bandwidth limit is, if possible, and check that against Shannon's Law. 4 KHz used to be the limit, but that may have been increased by some LECs to allow faster dial up access.

If you are out of range of DSL right now, wait a few months. My company is marketing a relatively simple and afordable DSL extenmder circuit, which should bring just about everybody into range.

Regards

John

 

[RomanKorobitsin]

My answer concerns the ProxyConn software. There are no any tricks or deception. They (the authors) claim that they can increase dial-up speed up to 5 times quicker. That’s true.

Proxyconn employs a variety of technologies to move web pages over the internet more quickly, all of which require no changes from the users or ISPs:

There are a number of special proxy servers all over the world (North America, Western Europe, Central and South America and in Asia Pacific) with automatic geographical load balancing among the servers.

You must install special software for working with one of these servers. This server caches the most popular webpages, blocks ads, compresses data, etc. and transmits this stream to the software installed on your computer. The absence of ads, caching improvements and special compression allows you to decrease traffic between your machine and this special server (actually decreasing your internet traffic).

Your software, after having received the data, decompresses them over special algorithm (their special protocol) and you look the pages in your web-browser as usual.

The authors also claim that Proxyconn's state-of-the-art compression technology compresses text data up to 10x and image data up to 3x, far higher than public standards.

So, it is really possible to increase the speed using this technology. But there are some drawbacks in my opinion. For example:

1) How do they define the criteria for cutting ads? It is possible that the necessary information might be cutted off;

2) Many webpages on the web have their special headers not allowing to cache them. So these pages must not and will not be cached according to RFC 2616;

3) A major part of images and other binary objects can be compressed up to 3x (as claimed) only with loss of quality;

4) Any other implications involved

For many people such a software is a good way to increase an Internet speed, for others not.

Roman Korobitsin,
Russia

 

[tomatge]

JohnFortier

What medium do you think DSL uses ?

DSL (operated in a variety of forms, the most common being ADSL for home internet connections) uses standard telephone wires. It operates at a higher frequency range than normal voice communications, and can therefore provide simultaneous voice and data capability. The reason that DSL technology was originally so expensive was that the DSL modem was attempting to use the telephone media and frequencies and rates greater that that it was designed for.

 

[Heydave]

DSL uses two frequency bands above the voice band on the phone line but these signals do not go through the voice switching system. The lower band is for upload data and the upper band is for downsteam. DSL requires a modem, filter, and router at the head end which is usually at the central office. This is significant added equipment and wire rerouting. That is the cost. As for the price, that is what the market will bear. Cable modem have about 60% market share compared to 40% for DSL. This has more to do with telephone company mismanagement than anything else. Now they are beginnning to loose even basic service. I doubt they are going to learn from their mistakes as they seem to convince themselves it is always sombody elses fault. It is as if they were making buggy whips and blaming their business downturn on the automobile business and the government for allowing them.

 

[johnwiss]

I understand two main problems with DSL--the twisted pair phone wire has a maximum useful range of about 15,000-18,000 feet without repeating. Also the access scheme as I understand allows fewer users per head-end modem at the DSLAM. Cable on the other hand uses a much better coax cable and a single modem at the head end CMTS can support more users due to higher bandwidth and a better MAC protocol.

As far as the dial-up "DSL-speeds" sre you telling us RomanKorobitsin that there is additional 5X compression above the already compressed V.90 standard? Regular pictures are already JPEG (stills) or MPEG (movies) compressed. I wonder if I downloaded a binary file if I would see any throughput increase--I bet not!

 

[Heydave]

The DSLAM does not have to be a bottleneck as it is a head end system presumably located near very fast data links. It is a deployment decision to serve the DSLAM with limited backbone. Cable systems use coax but it is shared with other users as well as TV and FM channels. Multiplexing is done by modems sharing a bandwidth.

 

[JohnFortier]

Johnwiss,

There is no practical limit to the numbert of users who can be served by the DSLAM. The major restriction on DSL is crosstalk, which increases with both frequency and number of DSL transmissions in a connecting cable bundle. One would think that the range would also affect the level of crosstalk, but, due to some interesting physics in the line, this is not true for far end crosstalk (FEXT), although it is true for near end crosstalk (NEXT).

My comnpany has been working for some time on a definitive solution to the crosstalk problem and this will be available in the very near future. At this point DSL will be capable of delivering 8 Mb/s doenstream and 1 Mb/s upstream.

I agree that the telephone companies have been very tardy and inefficient in their deployment of DSL in North America. In the rest of the world the story is very different, with DSL holding 60% of the market in Eurpope and increasing its lead, while the developed Pacific Rim countries have even greater penetration of DSL. America is at risk of becoming a DSL backwater.

What's the answer to the deployment problem? Well, we're working on that too, but it's a bit like pushing damp string uphill! The C-LECs want new technologies and new methods so they can compete against the cable companies, but the majors seem incapable of grasping the nettle and changing.

However, it would be a mistake to write DSL off in North America. The cable companies have invested huge quantities of borrowed or equity money in their infrastructure and they must service that debt. They can't raise their prices much further without driving their customers to DSL so they are in a bit of a cleft stick. DSL, on the other hand, uses already installed infrastructure, the majority of which is free from financial encumberance, so the telcos have a significant advantage, if they will sieze it.

Cable suffers from its own restrictions. For example, the spectral bandwidth of a co-ax is relatively limited, and only so many customers can be fitted into that bandwidth, along with the usual cable transmissions, which are broadcast and take up a fixed and significant portion of bandwidth. The only way for cable companies to overcome this problem is to increase the number of cable Optical Terminating Units in the field and the number of cables connected to them, which is a further investment which they will be hard pressed to finance.

Oh, and Tomatge; I'd just as soon not be lectured on DSL, it's a subject about which I am not too inexpert.

Regards

John

 

[RomanKorobitsin]

To johnwiss:

As far as the dial-up "DSL-speeds" sre you telling us RomanKorobitsin that there is additional 5X compression above the already compressed V.90 standard?

No I don't think so. Lool carefully at my post:

"A major part of images and other binary objects can be compressed up to 3x (as claimed) ONLY WITH LOSS of quality;"

So, I meant that is not possible to compress those images without loosing a quality.

Regular pictures are already JPEG (stills) or MPEG (movies) compressed. I wonder if I downloaded a binary file if I would see any throughput increase--I bet not!

I pointed out the drawbacks of their ideas and said it is up to one to choose this technology.