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Phone lines to 10/100

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July 27, 2004 5:26:50 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

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

More about : phone lines 100

Anonymous
July 30, 2004 1:14:42 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

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.

--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
Jordan wrote:




> 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








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Anonymous
July 30, 2004 4:17:35 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Dmitri(Cabling-Design.com wrote:

> 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.

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


--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Related resources
Anonymous
July 31, 2004 6:53:46 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

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 ;-)
--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------
J. Clarke wrote:

> Dmitri(Cabling-Design.com wrote:

>> 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.

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






##-----------------------------------------------##
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Anonymous
July 31, 2004 6:53:47 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Dmitri(Cabling-Design.com wrote:

> 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").

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.

> Looking around the Web you can find cabling
> manufacturers here and there starting to offer their 10G solutions like
> Krone, Siemon, Systimax.

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.

> 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.

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

> 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 ;-)

You should feel guilty for wasting your customers' money.

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
July 31, 2004 10:06:05 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

J. Clarke <jclarke@nospam.invalid> wrote:
> 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.

Nor I. I had heard that testing was proving trouble around
60m, and I'm not sure RJ-type connectors were still used.

>> 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 ;-)

> You should feel guilty for wasting your customers' money.

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
Anonymous
July 31, 2004 1:38:46 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

> J. Clarke <jclarke@nospam.invalid> wrote:
>> 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.
>
> Nor I. I had heard that testing was proving trouble around
> 60m, and I'm not sure RJ-type connectors were still used.

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.

>>> 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 ;-)
>
>> You should feel guilty for wasting your customers' money.
>
> They should, but salesmen are supposed to sell. Worse are
> the customer's managers who waste their shareholders money.

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 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.

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

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
July 31, 2004 8:24:10 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

J. Clarke <jclarke@nospam.invalid> wrote:
> Whose testing of what though? Remember, at one time 100
> megabit ran only a limited distance on special coaxial cables

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

> However in many cases the manager is not a technical person.

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

> 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.

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

> Salesmen are supposed to sell, but they also are supposed
> to establish relationships that get repeat business.

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

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

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

-- Robert
Anonymous
July 31, 2004 8:24:11 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

> J. Clarke <jclarke@nospam.invalid> wrote:
>> Whose testing of what though? Remember, at one time 100
>> megabit ran only a limited distance on special coaxial cables
>
> Yes, that's true. With sophisticated enough transceivers,
> Shannon's limit can be approach. But I don't believe beaten.
>
>> However in many cases the manager is not a technical person.
>
> Maybe not, but they should have enough wits to know it and
> then seek out appropriate unbiased advice.

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.

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

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."

>> Salesmen are supposed to sell, but they also are supposed
>> to establish relationships that get repeat business.
>
> Or get fired for not making enough sales _this month_.
> They too get sifted and migrated.

Or end up flipping burgers.

>> I don't think there's much "numerical justification"
>> going on.
>
> No, probably not. Then the shareholders deserve the
> waste their inattention causes.

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.


> -- Robert

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
August 1, 2004 2:49:54 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Robert Redelmeier wrote:

(previously snipped question regarding 10Gigabit ethernet)

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

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
Anonymous
August 1, 2004 2:49:55 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

glen herrmannsfeldt wrote:

> Robert Redelmeier wrote:
>
> (previously snipped question regarding 10Gigabit ethernet)
>
>> Yes, that's true. With sophisticated enough transceivers,
>> Shannon's limit can be approach. But I don't believe beaten.
>
> 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?

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

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

Soon as holographic TV becomes fashionable, most likely.

> -- glen

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
August 2, 2004 2:37:15 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote:

> 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.

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
Anonymous
August 2, 2004 2:37:16 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

> "glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote:
>
>> 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.
>
> 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.

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.

> Bert

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
August 2, 2004 2:37:16 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

> 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
>

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
Anonymous
August 2, 2004 2:37:16 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

> 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
>


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
Anonymous
August 2, 2004 2:37:16 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

> 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
>



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
Anonymous
August 2, 2004 7:54:36 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

CCIE8122 wrote:

(snip)

>> 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.

(snip)

> 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.

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.

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

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
Anonymous
August 2, 2004 8:10:27 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

(snip)

> 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.

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
Anonymous
August 2, 2004 6:51:48 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"CCIE8122" <none@none.com> wrote:

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

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.

> 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.

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.

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

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
Anonymous
August 2, 2004 7:14:39 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote:

> > [Shannon's law]: Capacity (in b/s) = bandwidth (Hz) * logbase2(1 +
S/N)
>
>
> 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.

That's okay, Glen. It doesn't change anything. The bandwidth of the
length of cable can be measured. If SNR is also a function of frequency,
you measure SNR at the bandwidth you have just determined the cable can
support.

> What to use for N?

The mistake some people make, when they claim or imply they have
exceeded the Shannon limit, is that they assume interference to be
noise. If some or all of the interference is from the main signal
itself, e.g. inter-symbol interference (which is caused by the symbols
traveling along the cable becoming distorted and then overlapping with
adjacent symbols) or just plain echo, this cannot be assumed to be
noise. This is signal energy, rather than energy from other sources. So
it must be considered to be S in Shannon's equation.

If you look at Shannon's equation, which I repeated above, it's clear
that the theoretical capacity in b/s will increase if the S of S/N is
computed as (signal + interference resulting from the main signal). N
has to be other sources of noise, which would include random white noise
as well as interference from unrelated signal sources.

> 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.

Absolutely. All in a quest to approach that elusive Shannon's limit.

Bert
Anonymous
August 2, 2004 7:20:56 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"J. Clarke" <jclarke@nospam.invalid> wrote:

> 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.

For a given length, this can be measured in straightforward fashion.

If Cat 5e can support 125 Mbaud over a 100 meter length, then for sure
its bandwidth must be greater than 100 MHz in a length of 100 meters.
Right? There is an upper limit, and I'm sure it will vary some between
cable brands.

Bert
Anonymous
August 2, 2004 7:20:57 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

> "J. Clarke" <jclarke@nospam.invalid> wrote:
>
>> 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.
>
> For a given length, this can be measured in straightforward fashion.
>
> If Cat 5e can support 125 Mbaud over a 100 meter length, then for sure
> its bandwidth must be greater than 100 MHz in a length of 100 meters.
> Right? There is an upper limit, and I'm sure it will vary some between
> cable brands.

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.

>
> Bert

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
August 3, 2004 12:08:14 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"J. Clarke" <jclarke@nospam.invalid> wrote:

[On Cat 5e]

> 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.

Lots of variables to be considered.

Reading quickly through IEEE 802.3-2002 Clause 40, it would seem that
using the 4 twisted pair in each direction, each one providing 250 Mb/s,
with PAM-5 modulation such that the symbol rate is only 125 Msymbols/sec
in each twisted pair, results in an attenuation of up to 11.8 dB per 100
meters. Is that the best the most up to date receivers can do? Maybe
not. Maybe greater attenuation can be survived, so the symbol rate can
be increased somewhat.

The modulation scheme used in 1000BASE-T is PAM-5. This allows for 2
bits of information to be transferred with each symbol. You send 2
b/symbol * 0.125 Gsymbols/sec * 4 lanes = 1 Gb/s total throughput. Is
that the best we can do? Maybe not. Maybe you can send 6 or 8 or 10 bits
per symbol, and still be capable of accurate decoding at the other end.

Clause 40 states:

"40.7.5 Noise environment

"The 1000BASE-T noise environment consists of noise from many sources.
The primary noise sources that impact the objective BER are NEXT and
echo interference, which are reduced to a small residual noise using
cancelers. The remaining noise sources, which are secondary sources, are
discussed in the following list."

Since crosstalk and echo can apparently be well compenated for,
according to Clause 40, is it possible to raise the signal level at the
source, to achieve a higher SNR than what is required for 1000BASE-T?
Maybe yes, in which case you'll have a better chance of decoding the
more delicate symbols required in the more complicated modulation
techniques than PAM-5 (e.g. 256-QAM, in which each symbol can represent
one of 16 amplitude levels and one of 16 phase variations from center
frequency, allowing for the transfer of 8 bits/symbol rather than just
2).

Without measuring cable bandwidth and noise levels in 100 meter
segments, and without knowing what the best receivers can accept in
terms of SNR today, it's impossible to compute the actual Shannon limit
of a 100 meter segment of Cat 5e. My guess is that we aren't even close
to it. But at the same time, getting closer costs money and development
time.

Bert
Anonymous
August 3, 2004 12:08:15 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

> "J. Clarke" <jclarke@nospam.invalid> wrote:
>
> [On Cat 5e]
>
>> 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.
>
> Lots of variables to be considered.
>
> Reading quickly through IEEE 802.3-2002 Clause 40, it would seem that
> using the 4 twisted pair in each direction, each one providing 250 Mb/s,
> with PAM-5 modulation such that the symbol rate is only 125 Msymbols/sec
> in each twisted pair, results in an attenuation of up to 11.8 dB per 100
> meters. Is that the best the most up to date receivers can do? Maybe
> not. Maybe greater attenuation can be survived, so the symbol rate can
> be increased somewhat.
>
> The modulation scheme used in 1000BASE-T is PAM-5. This allows for 2
> bits of information to be transferred with each symbol. You send 2
> b/symbol * 0.125 Gsymbols/sec * 4 lanes = 1 Gb/s total throughput. Is
> that the best we can do? Maybe not. Maybe you can send 6 or 8 or 10 bits
> per symbol, and still be capable of accurate decoding at the other end.
>
> Clause 40 states:
>
> "40.7.5 Noise environment
>
> "The 1000BASE-T noise environment consists of noise from many sources.
> The primary noise sources that impact the objective BER are NEXT and
> echo interference, which are reduced to a small residual noise using
> cancelers. The remaining noise sources, which are secondary sources, are
> discussed in the following list."
>
> Since crosstalk and echo can apparently be well compenated for,
> according to Clause 40, is it possible to raise the signal level at the
> source, to achieve a higher SNR than what is required for 1000BASE-T?
> Maybe yes, in which case you'll have a better chance of decoding the
> more delicate symbols required in the more complicated modulation
> techniques than PAM-5 (e.g. 256-QAM, in which each symbol can represent
> one of 16 amplitude levels and one of 16 phase variations from center
> frequency, allowing for the transfer of 8 bits/symbol rather than just
> 2).
>
> Without measuring cable bandwidth and noise levels in 100 meter
> segments, and without knowing what the best receivers can accept in
> terms of SNR today, it's impossible to compute the actual Shannon limit
> of a 100 meter segment of Cat 5e. My guess is that we aren't even close
> to it. But at the same time, getting closer costs money and development
> time.

Yup. And then a few years down the pike Moore's Law turns the multimillion
dollar laboratory curiosity into something that is standard equipment on a
child's plaything. When FDDI first shipped would you have ever thought
that something ten times as fast would be a $50/node consumer product that
ran over something not a whole heck of a lot fancier than phone wire?

> Bert

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
Anonymous
August 3, 2004 9:58:44 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

(snip)

> If Cat 5e can support 125 Mbaud over a 100 meter length, then for sure
> its bandwidth must be greater than 100 MHz in a length of 100 meters.
> Right? There is an upper limit, and I'm sure it will vary some between
> cable brands.

First order approximation, the bandwidth is half the baud
(transition) rate. Each cycle the signal makes two transitions.
Response can't fall too fast near that frequency, but that is
the number that is used in characterizing the cable, including
attenuation and crosstalk.

-- glen
Anonymous
August 3, 2004 6:32:48 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

J. Clarke <jclarke@nospam.invalid> wrote:
> Not gonna happen. I recall a few years back that [snip]
> The computers they acquired, specifically for the purpose
> of teaching MS-DOS, were Macs.

LOL! Just because stupidity abounds does not mean that
it is correct or even always occurs.

> I'll revise that--"if there are more ethical companies".

Certainly there are lots. You don't heard much about them
because bad news sells.

> Although I don't see it as a matter of ethics, I see it as a
> matter of non-techical types managing techs.

Non technical managers _can_ be the very best. The real problem
is when managers micromanage their employees. Even when they
have great technical strengths (wich sometimes means poor people
skills), they usually are missing information. Even when they
have it all, it's rather disrespectful of a competent professional
to meddle.

> the PHB comments "and those engineers, they're not exactly rocket
> scientists", to which Dilbert replies "well, actually, they are."

LOL! At NASA, certainly.

> Or end up flipping burgers.

Is that safe? We're talking about marketroids here!
I'm not sure they're competant.

> 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.

It doesn't matter whether there are many shareholders or only
one. All corporations have shares even if not publicly traded.
Conscientious owners are very careful what and how they manage.
More is not better. Keeping powder dry is an important concept.

-- Robert
Anonymous
August 4, 2004 12:02:26 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi <albert.e.manfredi@nospam.com> wrote:
> 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.

We can do better than assume. ADSL points the way to
some rough calculations:

Over short distances (3-5 kft), 6 (12?) Mbit/s are possible
and lets say that corresponds to your "whopping" 42.1 dB S/N.
Then voice-grade telco distribution UTP has a bandwidth of
at least 430 kHz.

Many people have trouble getting even 1.5 Mb/s at long
distances (15+kft), so the S/N must have dropped to 7 dB or
below. At least 3.5 dB/kft. How does that sound?

-- Robert
Anonymous
August 4, 2004 2:47:55 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Robert Redelmeier" <redelm@ev1.net.invalid> wrote:

> Over short distances (3-5 kft), 6 (12?) Mbit/s are possible
> and lets say that corresponds to your "whopping" 42.1 dB S/N.
> Then voice-grade telco distribution UTP has a bandwidth of
> at least 430 kHz.

That part sounds right.

> Many people have trouble getting even 1.5 Mb/s at long
> distances (15+kft), so the S/N must have dropped to 7 dB or
> below. At least 3.5 dB/kft. How does that sound?

Over long distances, the bandwidth of voice grade cannot be assumed to
still be 430 KHz, right? The high frequencies will be attenuated more
than the lower frequencies, as a function of cable length.

If the bandwidth is less than you assume, then it follows that the SNR
you need will be higher than you state.

Bert
!