From: Jongsoo kim (bstrt2002@gmail.com)
Date: Thu May 12 2005 - 18:18:16 GMT-3
This seems interesting topic so I like to drop some of my understanding
based on my experience.
At the end of day, as Scott said, it is a different way of transporting
bits. T1 is a T1.
The fundamental difference between DSL and T1 is PSK or QAM modulated
analog signal and bipolar pure digital signal( sync or square wave).
T1 is a bio-polar pure digital pulse( signal) and to send this signal
further, uses balance-transmission (tip and ring) so that it needs 2 wire
each direction.
DSL device modulates digital signal( ethernet or T1) into an analog signal
that can be specifically sent over the existing 2 wire of copper line(
RJ11).
Basically DSL is an advanced high-speed modem.
A modulated analog carrier can go much further compared to pure digital
signal like T1.( 6000 ft)
For exmaple, in my company, a modulated T1 is even radiated to
geo-stationary satellite without any wire( well, nobody can run the cable up
there).
Telco love to use this advantage of DSL to provide T1. Traditionally,
Bell(Verizon) brings in lucent OC-3 mux/M13/smart jack to provide T1's,
which is expensive solution if especially there is no infrastructure. But
with DSL, they can use the existing telephone wire without any Sonet
infrastructure. All they have to do is to de/modulate T1 into DSL carrier
over an existing 2 wire of copper ( oh well, a little bit more than that).
I think Telco would do in your building
Punch block <--two 2 wire --> DSL device<--T1 -->smart jack<-- T1--> your
device.
In CO,
DACS <-- channelized OC-3/DS3 --> DSL aggregate device <---- copper wire to
your building
Jongsoo
On 5/12/05, Anthony Pace <anthonypace@fastmail.fm> wrote:
>
> Is the conversion circitry actually in the smartjack itself on a chip?
> Does that mean that there is no clunky looking NIU cards (or whatever
> they are called)in old fashioned looking slots in the basement of that
> building anymore?
>
> So its:
>
>
>
CpeT1Device=>SmartjackSpittingOutDslOn1pair=>SinglePairWithNoRepeaters=>Dslam
AtCentralOffice
>
> Sounds like this is to maintain backwards compatitlity with the CPE
> device.
>
> Anthony Pace
>
> On Thu, 12 May 2005 15:58:39 -0400, "Scott Morris" <swm@emanon.com>
> said:
> > Actually, it boils down more to the oversubscription model used by
> > service
> > providers. People who have T-1's (synchronous and/or point-to-point
> > interfaces) get really pissy when the bandwidth they paid for isn't
> > available at random intervals.
> >
> > ADSL catered more to the way that traffic patterns exist at a consumer
> > level
> > and allowed service providers to work within the statistical probability
> > of
> > usage/bursty traffic. And the expectation was delivered to customers as
> > that of an "availble, but not always usable" bandwidth. T-1 never worked
> > that way.
> >
> > All traffic COULD still be muxed. Just depends on your engineering!
> > (and
> > your market expectations!)
> >
> > Scott
> >
> > -----Original Message-----
> > From: Anthony Pace [mailto:anthonypace@fastmail.fm]
> > Sent: Thursday, May 12, 2005 3:46 PM
> > To: swm@emanon.com; 'Hogo, Trust'; 'Group Study'
> > Subject: RE: T1 delievered on 2 wires or 4???
> >
> > Scott,
> >
> > again, very good info in your post! I know that HDSL was born out of the
> > desire to deliever the equivolent of a T1 on 1 pair, and that then the
> > other
> > tecnologies sparang up simutaneous to the TELCO laws changing (thus DSL
> > emerged as an alternative to serial point-to-point in that it could be
> > delievered by a CLEC renting 1 single loop from the ILEC)
> >
> > I know that T1's are ferquently MUXED onto ATM and then transparently
> > delievered as to the CPE gear on either end as serail T1, but if it's
> > going
> > to a last mile of something other than a T1 (ESF with all the signalling
> > bits and CRC and all the stuff backward compatible to 1962) why not just
> > sell and deliever the new and improved DSL (whatever
> > flavor) right into the CPE device (router in my case).
> >
> > Is it just the idea of a T1= good and DSL=bad for marketing purposes? Or
> > is
> > it just to be able to hand the customer what they want (T1) and then
> > finding
> > the best technical approach (separate form the terminology being used to
> > sell it)
> >
> > does that question make sense? probobly not.
> >
> > Anthony Pace
> >
> >
> >
> >
> > On Thu, 12 May 2005 15:25:54 -0400, "Scott Morris" <swm@emanon.com>
> > said:
> > > Hehehe... Telco Voodoo Magic. :)
> > >
> > > It's just a way to transport bits. The design concepts behind ADSL
> > > (shared medium with varying xfer rates) are significantly different at
> > > the telco-side of things than designing for HDSL or VDSL. So the
> > > assumptions people have about DSL in general don't always apply.
> > >
> > > For the telcos, it's all about conserving wire pairs. Physical
> > > infrastructure is a pain in the butt to fix, upgrade and change out.
> > > So any reuse is great!
> > >
> > > Where can you learn more about it? Hmmmmm... Good question.
> > > www.protocols.com <http://www.protocols.com> perhaps, or Newton's
> Telecom Dictionary. It's just
> > > part of my vast collection of useless knowledge from working in the
> > > field so long!
> > >
> > > HTH,
> > >
> > > Scott
> > >
> > > -----Original Message-----
> > > From: Anthony Pace [mailto:anthonypace@fastmail.fm]
> > > Sent: Thursday, May 12, 2005 3:11 PM
> > > To: swm@emanon.com; 'Hogo, Trust'; 'Group Study'
> > > Subject: RE: T1 delievered on 2 wires or 4???
> > >
> > > Scott,
> > >
> > > This is very good information. Where can I learn more about it?
> > >
> > > ok. So people have come to believe T1=good DSL=flakey and opted for
> > > the old tried and true 4 wires delieverd by the ILEC, with many
> > > repeaters along the path; rather than gamble on DLS delievered by the
> > > CLECS. BUT now the smartjack accepts the 4 wires comming from my
> > > router interface and converts it to DSL so that it can be transmitted
> > > on 2 wires - and then does the same conversion at the other end of the
> > > circuit (keeping the entire process transparent to me)
> > >
> > > Anthony Pace
> > >
> > >
> > >
> > >
> > > On Wed, 11 May 2005 18:30:40 -0400, "Scott Morris" <swm@emanon.com>
> > > said:
> > > > A T-1 is 2-pair or 4 wires.
> > > >
> > > > However, many of the smartjacks are now HDSL capable (or VDSL
> > > > depending on proximity to CO) and that is delivered over a single
> > > > pair or two wires.
> > > >
> > > > The smartjack is doing magical conversion between the two. ;)
> > > >
> > > > HTH,
> > > >
> > > > Scott
> > > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > > > Of Hogo, Trust
> > > > Sent: Wednesday, May 11, 2005 6:05 PM
> > > > To: Anthony Pace; Group Study
> > > > Subject: RE: T1 delievered on 2 wires or 4???
> > > >
> > > > Hope this might help.
> > > >
> > > > http://www.cisco.com/warp/public/788/products/vwicmf_t1.html
> > > > http://www.cisco.com/warp/public/63/wic-1dsu-t1.html
> > > >
> > > > ------
> > > > HQ
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > > > Of Anthony Pace
> > > > Sent: Wednesday, May 11, 2005 4:50 PM
> > > > To: Group Study
> > > > Subject: T1 delievered on 2 wires or 4???
> > > >
> > > > I recently terminated a T1 and ISDN PRI in a remote location and was
> > > > able to see that the TELCO had terminated the T1 using a single pair
> > > > and the PRI using a single pair from the 25 pair bundle coming into
> > > > the Data Center's smart jacks.
> > > >
> > > > I was always under the impression that from the CSU/DSU (in my case
> > > > it was built into the router) to the smartjack and subsequently the
> > > > NI card in the MPO was 4 wires. 1 pair TX and 1 pair RX.
> > > >
> > > > Maybe between the CSU/DSU and the NI card it's 2 wires and then 4
> > > > for the distance to the CO? ??? I am confused because I always
> > > > believed that DSL was born out of the efforts of finding a single
> > > > pair alternative to
> > > > T1 technology.
> > > >
> > > > Should PRI and DS1 be 1 pair or 2?
> > > >
> > > > Anthony Pace CCIE 10349
> > > >
> > > > --
> > > > Anthony Pace
> > > > anthonypace@fastmail.fm
> > > >
> > > > ____________________________________________________________________
> > > > __ _ Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > > ____________________________________________________________________
> > > > __ _ Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > > >
> > > --
> > > Anthony Pace
> > > anthonypace@fastmail.fm
> > >
> > --
> > Anthony Pace
> > anthonypace@fastmail.fm
> >
> --
> Anthony Pace
> anthonypace@fastmail.fm
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Fri Jun 03 2005 - 10:11:57 GMT-3