Phone lines to 10/100

Hi to all,

I am working in a company stablished in an old building and we have a BNC network (limited to 10Mhz).

Rewiring the building to install a 10/100Mhz is very dificult (or impossible).

In all working places I have a phone conection throught a switchboard (centralita telefonica) and I wish to know if there is any system to convert the phone lines in phone+ethernet as DSL works.

Thanks to all,

Jordan Gomila

Reply to
Jordan
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You may want to consider using the old cables, BNC and phone, as pull strings for brand new CAT5E or CAT6 cables. You are not going to have any benefit of switching to DSL-like technology as it would still be below the

10Mb/s that you presently have. Well, not it's not only 10Mb/s, but it is also shared media, so there may be some benefits, but negligible in comparison to upgrading your cables to CAT5E or CAT6. You actually may want to go right to CAT6 as you probably wouldn't want to install cables again when 10GBit/s becomes mainstream.
Reply to
Dmitri(Cabling-Design.com

Do you have any reason to believe that 10000baseTwhatever is going to require CAT6? Last I heard they were targetting 5E.

Reply to
J. Clarke

Is that IEEE standard 10G or is that some proprieatary solution? I was not aware that a standard for 10G over UTP had been released.

They have a "10G solution"? You mean they have a MAC, PHY, the whole nine yards? Or just some ovepriced cabling system that they're trying to get people to buy on the basis of FUD advertising about 10G?

Anybody who believes the advertising of cable manufacturers should be very careful about talking to New Yorkers about bridges, Iowans about ski resorts, and Floridians about beachfront property.

Has the IEEE stated that cabling beyond CAT5E will be required?

You should feel guilty for wasting your customers' money.

Reply to
J. Clarke

Last time I checked 10G was reported to work only 60 meters on a regular CAT6, which brings to life CAT6E (or CAT6A to that matter as they tend to call it "augmented CAT6"). Looking around the Web you can find cabling manufacturers here and there starting to offer their 10G solutions like Krone, Siemon, Systimax. It is unlikely that CAT6A will become a standard in less than two years, so for now it will be "just standard-compliant" CAT6 and "10G certified" CAT6. I feel really uneasy about the customers that we sold CAT6 systems to in the last three-four years as the sales pitch was about future-proofing... Well, that's not us, that the Moore's law they should blame ;-)

Reply to
Dmitri(Cabling-Design.com

Nor I. I had heard that testing was proving trouble around

60m, and I'm not sure RJ-type connectors were still used.

They should, but salesmen are supposed to sell. Worse are the customer's managers who waste their shareholders money.

I don't know how people numerically justify "futureproofing". If spending ~20% more on the install now has a 1/3 chance of saving a recable in 10 years, that investment has an IRR of 7.2%. Very few organizations have hurdle rates that low.

-- Robert

Reply to
Robert Redelmeier

Whose testing of what though? Remember, at one time 100 megabit ran only a limited distance on special coaxial cables and it was believed that fiber was needed for general use. Later the same was true of gigabit. Right now there may be a 10G implementation that runs on short lengths of special cable but that does not mean that that implementation is the one that is going to be implemented in the release spec whenever it happens.

Sounds like what you're talking about is a standard for interconnectivity in the data center, not general deployment.

However in many cases the manager is not a technical person. Personally my experiences have been such that I rank the people who run cabling companies somewhere below lawyers--what really pisses me off is when the tech who knows how to do it right has to choose between doing it wrong to pinch a penny or meet a deadline and getting fired.

Salesmen are supposed to sell, but they also are supposed to establish relationships that get repeat business. If you need two more drops and you remember "Oh, Joe Blow Cable is the outfit that sold us that overpriced cable" then you look elsewhere for those two drops. And as your business grows and one day you have a 20 story building to cable . . .

I don't think there's much "numerical justification" going on.

Reply to
J. Clarke

Not gonna happen. I recall a few years back that the Connecticut state vocational/technical schools discovered that in most of their classes on DOS applications the instructor was spending more time teaching basic DOS commands than teaching the application. So it was decided that the schools would teach every student the basics of DOS and classrooms were assigned and computers acquired. The computers they acquired, specifically for the purpose of teaching MS-DOS, were Macs. Several people complained to their legislators--I saw one of those responses--seems that the legislature had a pet "expert" who was a Mac advocate.

If there are "more ethical companies" hiring. I'll revise that--"if there are more ethical companies". Although I don't see it as a matter of ethics, I see it as a matter of non-techical types managing techs. Reminds me of the episode of whatever that TV show was that was based on Dilbert (the live-action show, not the cartoon), in which the PHB comments "and those engineers, they're not exactly rocket scientists", to which Dilbert replies "well, actually, they are."

Or end up flipping burgers.

There are not always shareholders involved. Every company is not publicly traded you know. Some big ones (Johnson's Wax for example) are privately held. But this is a level of micromanagment that it is unreasonable to expect of even the most conscientious shareholders.

Reply to
J. Clarke

Yes, that's true. With sophisticated enough transceivers, Shannon's limit can be approach. But I don't believe beaten.

Maybe not, but they should have enough wits to know it and then seek out appropriate unbiased advice.

Such knowlegable techs are then just forcibly migrated to more ethical companies.

Or get fired for not making enough sales _this month_. They too get sifted and migrated.

No, probably not. Then the shareholders deserve the waste their inattention causes.

-- Robert

Reply to
Robert Redelmeier

There's no "requirement" for this, it's just that that's the way things have worked out so far.

Soon as holographic TV becomes fashionable, most likely.

Reply to
J. Clarke

(previously snipped question regarding 10Gigabit ethernet)

For a phone line, Shannon's limit is pretty strict, especially as most are digitized at 64000b/s somewhere along the way.

For UTP cable, the limit is not so sharp. Attenuation increases pretty fast with increasing frequency, but that can be corrected. Some noise sources can also be corrected, such as using echo cancellation techniques. With increasing work on transceivers there may still be some distance to go.

One complication, though, is ethernet's requirement to only increase in factors of ten. If 20Gb/s or 30Gb/s could work on Cat 5e cable, would it be worth doing?

How soon will 10Gb/s to the desktop be needed?

-- glen

Reply to
glen herrmannsfeldt

This is all well and good, but for purposes of Shannon's Law calculations, what is the "bandwidth" of CAT5E cable? And don't say "100 MHz"---that's what it's _tested_ to, not any kind of hard upper limit.

Reply to
J. Clarke

That may be in theory, but the reality is that is not possible. Not at least with today's deployed TDM networks.

The reason is that the carrier is MUXing those 64k DS0 lines into DS-1s, DS-3s, and then to optical circuits to transport across IOF or to interconnect with IXCs.

So while as a practical matter you may be able to get up to 56k (i.e.,

64 less the 8k in-band signalling) by removing filters, you really arent going to exceed that, filters or no. They just cant cram that kind of bandwidth onto a DS0 channel, and to deliver DS-1 to the prem would require massive redeployment of electronics, both in the CO and at the prem.

Hence the proliferation of broadband signalling that circumvents the TDM world and acheives the type of bandwidth you are talking about (and then some).

kr

Reply to
CCIE8122

That may be in theory, but the reality is that is not possible. Not at least with today's deployed TDM networks.

The reason is that the carrier is MUXing those 64k analog lines are mapped onto DS0 channels which are MUXed into DS-1s, DS-3s, and then to optical circuits to transport across IOF or to interconnect with IXCs.

So while as a practical matter you may be able to get up to 56k (i.e.,

64 less the 8k in-band signalling) by removing filters, you really arent going to exceed that, filters or no. They just cant cram that kind of bandwidth onto a DS0 channel, and to deliver DS-1 to the prem would require massive redeployment of electronics, both in the CO and at the prem.

Hence the proliferation of broadband signalling that circumvents the TDM world and acheives the type of bandwidth you are talking about (and then some).

kr

Reply to
CCIE8122

That may be in theory, but the reality is that is not possible. Not at least with today's deployed TDM networks.

The reason is that those 64k analog lines are mapped onto DS0 channels which are MUXed into DS-1s, DS-3s, and then to optical circuits to transport across IOF or to interconnect with IXCs.

So while as a practical matter you may be able to get up to 56k (i.e.,

64 less the 8k in-band signalling) by removing filters, you really arent going to exceed that, filters or no. They just cant cram that kind of bandwidth onto a DS0 channel, and to deliver DS-1 to the prem would require massive redeployment of electronics, both in the CO and at the prem.

Hence the proliferation of broadband signalling that circumvents the TDM world and acheives the type of bandwidth you are talking about (and then some).

kr

Reply to
CCIE8122

Shannon's law is the limit, after you've taken whatever measures you're going to implement into account. It does not state how you achieve that limiting usable bit rate, it just tells you what the usable bit rate will be. And it depends on the bandwidth (in Hz) of the transmission medium and the S/N ratio on that medium. S/N ratio, not the ratio of (for example) the main signal to noise + echo (S/[N + E]). The S/N ratio, in turn, would be affected by the length of the medium.

Capacity (in b/s) = bandwidth (Hz) * logbase2(1 + S/N)

Note: S/N is a ratio, *not* expressed in dB in the equation above.

In practice, if you hope to approach the Shannon limit, you would make constructive use of echo energy and you will also implement a good error correction code. By "constructive use," I'm saying that you would equalize the channel so that echo energy is added to the energy of the main signal, so the S/N ratio will actually consist of ([S + E] / N).

Let'e say for example that the Shannon limit is 30 Mb/s for a particular link. You are free to pump 1 Gb/s through that link, but that will create lots of errors. So if you want to keep throwing 1 Gb/s at the link, you'll want to introduce error correction techniques, which will use up some of that bit rate. Shannon's law predicts that the very best you can do, whether you try 1 Gb/s and then add error correction, or whether you simply lower the transmitter's raw bit rate, or a combination of such techniques, will be to achieve a usable 30 Mb/s.

I guess what I'm saying is that the practical manifestation of Shannon's law might not appear sharp, but that doesn't mean that you'll violate the limit. It just means that as you approach the limit, you will have to endlessly tweak all your error correction, echo cancelling, and any other trick you're trying.

For a regular POTS phone line, limited deliberately to 4000 Hz by your baby Bell, Shannon's law says that you can achieve 56 Kb/s only if your S/N ratio is a whopping 42.1 dB.

On the other hand, if your baby bell eliminates the 4 KHz filters from your POTS telephone line, things would be different. Assume the voice grade UTP has a bandwidth more like 50 KHz, just for the sake of argument. Now you can achieve 64 Kb/s with just 1.55 dB of S/N. In fact, if you can actually achieve an S/N ratio of 42.1 dB as you had above, by eliminating those 4 KHz filters your voice grade cable will now be able to carry 700 Kb/s.

Bert

Reply to
Albert Manfredi

(snip)

(snip)

Stories used to be that it would work within a single exchange. I don't know if there are still any analog switches left, though.

Also, loading coils are put on most longer phone lines, which are effective as 4kHz filters, even though that isn't their goal. Phone systems run 600 ohm source and load impedance on wire with a much lower characteristic impedance. The result is that it looks like a capacitor. Appropriate amounts of series inductance spaced along the cable counteract the capacitance, at the same time making a sharp low pass filter.

As I understand it, the best way to do it is to buy a dedicated wire pair as commonly used for burglar alarm systems. It doesn't go through any switch, just directly between you and the destination (which is supposed to be a burglar alarm service center).

I believe that can also be done for T1 lines if the distance is short enough.

-- glen

Reply to
glen herrmannsfeldt

(snip)

For UTP cable, the S/N depends on frequency, so you can't use such a simple formula. You should integrate the bandwidth as times log2(1+S(f)/N(f)) over the appropriate frequency range.

What to use for N? Ethernet makes some assumptions on what the likely noise is, allows for a safety margin, and uses what is available. It would be possible to make an adaptive system, somewhat like some modem systems do, where the capacity used depends on the available signal to noise ratio.

Error correcting codes can also be used.

-- glen

Reply to
glen herrmannsfeldt

Yes, it can support 100. Can it support 200? 500? 1000?

I was actually thinking more about another branch of the thread I think in which it was being argued that 10 gig was going to require some fancy new cable, than about what's achievable over phone line.

Reply to
J. Clarke

It's not only possible, it is exactly what happens when you order an ADSL line to your home. The speed you get will depend on the frequency bandwidth possible between your home and the phone company's closest central office, where these voice grade cables terminate. Which is, of course, in part a function of distance. The first thing that happens when you order an ADSL line is that the phone company sends a truck to remove the 4 KHz filters between your home and the CO. A time consuming job, apparently, because the location of these filters is not always well documented.

Which has nothing to do with the voice grade link to the CO. Once the signal from the copper twisted pair is placed on a faster trunk cable, Shannon's equation will depend on the bandwidth of this bigger trunk cable. The same law still applies, but now you aren't talking about a voice grade UTP cable anymore.

And it still isn't violating Shannon's equation. You have merely changed the parameters going in. And by the way, TDM or FDM or packet switching is not the issue. The total aggregate bit rate is what Shannon's law addresses. You can of course always reduce the efficiency of a link by introducing wasted time intervals, but you can't do better than what Shannon predicts (at least, hasn't happened yet).

Bert

Reply to
Albert Manfredi

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