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From pub-infra-request Tue Dec 10 13:34:55 1991
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Subject: What is ISDN Good For?
From: mkapor (Mitch Kapor)
Sender: ckd
habs@panix.com (Harry Shapiro) writes:
"What applications that require ISDN can't already run with existing
products like switched 56 kbit, and 14,400 modems?"
Switched 56 kilobit service has the same order of bandwidth as 64 kbit
ISDN, but its availability is strikingly different. Switched 56 is not
intended to be a residential service. Our vision of ISDN is that you
simply order it the way you order an additional voice-grade phone line.
Further, we believe ISDN must be priced like voice telephone service.
Switched 56 is not priced like voice service. It is much more
expensive. ISDN must be ubiquitous and affordable. Switched 56, while
useful for businesses which can afford expensive installation and fees
is not.
The ISDN rate of 64 kb is at the critical threshold which will permit
interactive multimedia using video and audio compression. 14.4 is
simply too slow, even with compression, for videotelephony, much less
other more demanding forms of video. Before it is argued that the
effective rate of a V.32bis modem is not 14.4 kb, but 14.4 kb plus
compression effects, let me point out that the same compression
techniques can and will be applied over 64 kb ISDN lines, boosting its
effective rate by an equivalent factor of two to four.
While it is still considered heretical in some quarters to assert that
VHS-quality video will be possible over a 64 kb line, there is a growing
consensus among researchers at the cutting edge of work in this area
that that is exactly where we are headed. In such a scenario, using
desktop personal computers of the year 1995 as video production studios,
everyone with access to a PC and ISDN potentially becomes a video
producer, with ISDN as the switched distribution network providing video
dial-tone. This will open the floodgates of innovation in video,
acheiving the richness of video (not passive, but interactive) with the
type of diversity heretofore associated only with print.
Beyond ISDN are other protocols which can run over copper-pairs, such as
ADSL, which runs at 300 kb /second. More on that later.
Mitchell Kapor
Electronic Frontier Foundation
From pub-infra-request Tue Dec 10 13:33:37 1991
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Date: Tue, 10 Dec 1991 18:33:37 -0500
Message-Id: <199112102333.AA05559@eff.org>
Subject: ADSL
From: mkapor (Mitch Kapor)
Sender: ckd
habs@panix.com (Harry Shapiro) writes:
If we really want to have competition for the Cable and Telco
companies we need a digital product that can let Telco deliver movies
and entertainment at VCR quality and above... It is within the
technical ability of cable companies to offer phone service, plus
cable and other people offering PCN.
ADSL can be used to offer VCR quality video, using compression
techniques to most homes.
ADSL, is a T1 speed (1.54 mbits) connection into the home
with a 16 kbit up to 144 kbit bi-directional (base rate isdn)
connection.
Uncompressed CD audio, compressed NTSC, computer graphics, etc. All
this can be offered within a T1 rate. (All most anything we (as
consumers) want, t1 could do... Yes some of us want 45 mbits and
some of us what even more....
ADSL (Asymmetrical Digital Subscriber Line) is still in field trials.
It will be in trials in the 92/94 time frame...
The sept. 16, 1991 -page 18- issue of computer world reports,
"ADSL, developed by Bell Communications Research Inc., (Bellcore)
delivers a bitstream of 1.5M bit/sec. to homes with two-way,
Basic-Rate Integrated Services Digital Network (ISDN)"
The August 26 th 1991 issue of FIBER OPTIC NEWS on page 8, reports,
"VCR quality television, voice and data can be sent simultaneously
over a single cooper telephone line... The achievement is possible
because of ... ADSL which uses digital signal processing techniques
and experimental very-large-scale integrated (VLSI) circuitry."
The June 10th issue of Telephony on page 27 reports,
"ADSL... has a design goal of 18,000 feet on just one copper pair....
The Technology
The anticipated range of ADSL equipment using quadrature amplitude
modulation (QAM) is from 0 to 18,000 feet. About 75% of residential
telephone customers are served today on non-loaded facilities less
than 18,000 feet from the CO."
[We agree. ADSL sure sounds like a good thing. We are finding out what
Bellcore and RBOC deployment plans are, if any. As previously noted, we
think video over ISDN is a valid medium. But faster is clearly better,
especially if it still runs over copper. -MK]
My point being lets not spend public money on things like ISDN,
when something better and more useful is coming.
[We're not advocating spending large amounts of additional public money on
ISDN. Telco plant modernization for digital switches etc. is going to
happen whether or not consumers get ubiquitous, affordable ISDN. We're
paying for it anyway. -MK]
From pub-infra-request Tue Dec 10 13:35:47 1991
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Date: Tue, 10 Dec 1991 18:35:47 -0500
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Subject: Initial Positive Response to the Open Platform Proposal
From: mkapor (Mitch Kapor)
Sender: ckd
The initial response to the Open Platform concept has been extremely
positive in many quarters.
1. Congress
In a letter to Mitchell Kapor from the Chairman of the Subcommittee with
primarily jurisdiction over telecommunications policy dated November 5,
1991, Representative Edward J. Markey complemented Mitchell Kapor on his
"insights on the development of a national public information
infrastructure" which "were appreciated greatly by myself and the Members
of the Subcommittee."
Chairman Markey, writing to Mitch Kapor as a representative of the computer
industry, called for other leaders in the industry to participate more
actively in the policy process. The letter states:
"In crafting the right policies [for the telephone network], the assistance
of you and your colleagues in the computer industry is critical if we are
to bring the benefits of advanced information technology to the American
public. As I said at the hearing, we need to pursue policies that
encourage the Bell companies to work with other sectors of the
communications industry to create a consumer-oriented, public information
network. Please let me or my staff know what policies you and others in the
computer industry believe would best serve the public interest in creating
a reasonably priced, widely available network in which competition is open
and innovation rewarded. I also want to learn what lessons from the
computer industry over the past ten to fifteen years should apply to the
current debate on structuring the information and communications networks
of the future....I ask your help in gaining input from the computer
industry so that the Subcommittee can shape policies that will bring this
spirit of innovation and entrepreneurship to the information services
industry.
Key members on the Senate Commerce Committee have also expressed serious
interest in the proposal and for it to be further developed in cooperation
with others in the computer industry. We have agreed to reach out to
leaders in the computer industry such as yourself to obtain your input and
seek your participation in this policy process.
2. Communications Industry
Since unveiling the proposal, Mitchell Kapor and Jerry Berman, EFF's
Washington Office Director, have met with top officials of many of the
communications and electronic publishing firms involved in the current
debate, including the American Newspaper Publishers Association, the
National Cable Television Association, Dun and Bradstreet, AT&T, and the
Electronic Publishers Association. All have expressed enthusiasm about the
Open Platform concept and have urged that we develop the proposal in more
detail. They want to know if it is both economically and technically
feasible to deploy a feature rich ISDN or whether innovation must await the
full and costly deployment of residential fiber optics.
3. Consumer Groups
On November 25, 1991 the Communications Policy Forum, a consumer forum
cosponsored by the Consumer Federation of American, the Electronic Frontier
Foundation, and the American Civil Liberties Union, met to discuss the
future of telecommunications policy in the wake of the court's decision to
permit the RBOCS to engage in information services. At this meeting, EFF
presented the Open Platform Proposal as a necessary part of any legislation
that seeks both to establish fair competition as well as innovative health,
education, and other information services. Consumer groups expressed
great interest in the idea and called on EFF to develop its concept further
and to use the Communications Policy Forum as a mechanism for developing a
more detailed open platform design for further consumer review in early
1992.
From mkapor Tue Dec 10 14:43:29 1991
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From: mkapor (Mitch Kapor)
Subject: Tutorial on Telephone network architecture
[Tim Gorman <71336.1270@compuserve.com> provides the following useful
tutorial on ISDN in the telephone network. -MK]
Probably the first comment that needs to be made about ISDN availability is
the capability of the network to provide the service. There are several
pieces of the network involved in providing the service and all must be
available or none of the rest are useful. Basically these consist of:
1. local subscriber outside plant facilities
a. copper pairs
b. Subscriber carrier (either copper or fiber based)
2. Central Office line card modules (and corresponding line cards)
3. Central office line concentrating modules (primarily software)
4. Central office interoffice trunk modules
5. Central office switch generics
Central office
---------------
First, some generic background on central office switch architecture is
needed. For the most part, the following descriptions apply to all
digital central offices regardless of vendor.
| | | | | | | |
|dist. |_____|line |_____|concentrating|_____|switch |__________
|frame | |cards| |module | |fabric | |
| | | | | | |interface| |
|______| |_____| |_____________| |_________| |
| |
| |
| | | |
Subscriber |trunk | |
Outside interoffice ________|interface |_________|
Plant facilities |module |
|__________|
| | (controls the interoperation of
|Central | the modules and some of the
|Processing| complex internal operations)
|Unit (CPU)|
|__________|
The line card module, concentrating module, and switch fabric module are
all
smart, highly sophisticated pieces of equipment. Although some call them
"multiplexing" equipment, in essence they are all dedicated purpose
computers. As such, they all have software (or firmware or whatever is
appropriate to the vendors architecture and jargon) which dictate their
operation. In many cases, this software is arranged as various packages or
"features" that are licensed (via a right-to-use fee) from the vendor.
These
software features include software for the various module operations as
well
as for the CPU "generic" software. ISDN functionality is usually included
as
one or more of these features (e.g. basic ISDN, D-channel packet, D-channel
backup could all be different feature packages).
There may be multiple physical variants of each module for use in providing
different serving arrangements in different switches. These may also many
times be distinguished by different pricing levels. At least one vendor has
available a standard, analog line card/line drawer/line frame module and a
different ISDN, 2B1Q compatible line card/line drawer/line frame module.
The
2B1Q ISDN line frame module is to be upgraded in 1992 to be physically and
software compatible with all standard analog line cards as well as the ISDN
2B1Q line cards.
Network
-----------
Making ISDN a viable service will require providing the right physical
equipment and software in the network. Individual physical pieces that
will need to be considered are:
a. line terminating equipment
b. interoffice trunking equipment (for 64kb clear channel signaling)
c. interoffice facilities (for 64kb clear channel signaling)
d. subscriber loop carrier equipment
It is probable that most existing line terminating equipment is not ISDN
capable. The primary reason in most cases will probably have to do with the
need for splitting off the D-channel signaling and routing it through the
switch to the necessary processing modules. Most existing line module
equipment just doesn't provide for this. This does, of course, depend on
the switch vendors equipment design.
Most trunk interface module equipment now in use is not 64kb clear channel
signaling capable. For at least two major switch vendors, making the
equipment capable will not require provisioning new equipment modules but
will require adding "common equipment" to the existing modules. The common
equipment consists of additional plug-in boards providing the necessary
functionality. The major problem with this upgrade is the complexity of
adding these plug-ins. If you have a trunk interface module that handles
twenty DS-1 lines and they are all in service only two approaches are
available. You can obtain "turn-down releases" on all of the circuits,
busy them out, perform appropriate maintenance activity on the interface
module, add the new circuit packs, download any needed software to the
trunk interface peripheral, and then reverse the previous steps to put the
circuits back in service. The alternative is to provide a "conversion"
trunk interface module (properly equipped of course), transition all DS-1
lines from the next module to be converted to the conversion module,
convert
the just vacated one, and then continue the process with the next module in
line and the one that was just converted. Both methods are VERY manpower
intensive and therefore expensive to perform. It is also not a quick
process
in terms of overall interval. Manpower must be allocated to this task when
other, higher priority service-impacting activities are not pending.
Providing full ISDN capability in the interoffice facility network is much
like providing it in the central office trunk interface modules.
Multiplexing
equipment, fiber terminating bays, line repeaters, etc. must be changed out
or upgraded. The major complicating factor here is the number of circuits
that can be involved and the resulting service impacts.
Subscriber Loop Carrier
--------------------------
Subscriber Loop Carrier (SLC) was developed to take advantage of DS1
signaling to save outside plant investment. By using two pairs to provide
a DS1 span with a capability of 24 circuits, a savings of 22 pairs could be
realized. Most Subscriber Loop Carrier (SLC) equipment being provided today
operates much in the same fashion as standard T-1 equipment. This means
each
individual module provides some kind of grouping of 24 56kb lines.
Different
vendors provide different line capacities such as AT&T's SLC-96 (tm?)
equipment. In order to provide full ISDN capability the equipment must
first
be upgraded to provide 64kb channel service instead of 56kb. Then the
appropiate plug-in cards must be installed to interface with the actual
pair
going toward the subscribers location. The major concern in this serving
arrangement will be the impact on equipment quantities. To serve 2B+D at a
160kb rate will probably require three channels (64kb * 3 = 192kb) on the
SLC module. A large penetration of ISDN could result in having to increase
equipment investment to a level of about three times what it is now. Some
investigation also is needed to determine if ISDN and standard analog lines
can co-exist on the same SLC module. If not, even a small penetration of
ISDN could result in a large requirement for additional equipment.
Generic SLC architecture looks as follows:
24
24
subscribers
| | Lines | | |SLC | DS1 | | __
|Line | |Dist | |Central | |SLC | o/ \o
|Interface|_______|Frame|_______|Office |_____//_______|Remote |____/\
|Module | | | |Terminal| // |Terminal| / \
|_________| |_____| |________| |________| ----
2 lines
(1-transmit)
(1-receive )
The arrangement shown here is what is generically termed "dedicated" mode.
Each subscriber has a channel to the switch available at all times. Most
vendors offer enough intelligence in their terminals (usually via
additional
plug-ins) to also provide concentration ratio's ranging from 48 subscribers
vying for 24 channels (2:1) to as high as 5:1. This would mean that of the
120 customers connected to the remote terminal, only 24 could have calls in
progress at once.
One primary reason for for SLC equipment not being exactly like standard T1
systems is the need to provide for additional signaling modes required in
the
loop plant. Interoffice trunk signaling generally uses what is termed
2-State
signaling. The far end can signal you as either off-hook or on-hook
(busy/idle, seizure/idle, etc.) Similarly, you can signal the far end an
off-hook or on-hook. Physically, this signaling can take many forms: loop
closed/loop open, battery reversal/normal battery, E lead ground/E lead
open,
etc. Basic station service typically uses 3-State signaling from the
Central
Office (CO) toward the station and 2-State from the station to the CO. The
CO
needs to signal battery applied to the line, battery not applied to the
line,
and alerting (usually ringing voltage). Special stations such as ground
start
lines or coin lines can use 3-State signaling or even higher (the CO needs
to signal a coin station for coin collect, coin return, dialing pad enable,
dialing pad disable, and ringing among others). This requires the SLC
equipment to encode the signaling information in the PCM bitstream
differently than standard T1.
As an enhancement to this service, some switch vendors make what is termed
"integrated" SLC modules for their switches. All this really does is take
the
central office terminal and integrate it directly into the switch
architecture. The DS1 lines from the remote terminal can then be terminated
directly on the central office switch. This architecture has never "caught
on" in this area because of the difficulty in maintaining load balance
objectives (i.e. you can't move a high usage line to a low usage line
interface module to keep switch usage in balance without moving at least
23 other customers).
Interoffice Facilities
----------------------
In general, interoffice facilities are arranged as follows:
| |________| | | |
|CO | DS1 |DS1 | |Light Fiber |
|Trunk |________|to | |Terminating Bay |
|Interface|________|DSx |________| or |______\ WORLD
|Module |________|Multiplexer| |Digital Radio Bay| /
|_________| |___________| |_________________|
LFTB - Light Fiber Terminating Bay
DRB - Digital Radio Bay
MUX - DS1-to-DSx Multiplex/Demultiplex Bay
DSX - Digital Signal X-conn (cross-connect) Bay
COTIM - Central Office Trunk Interface Module
DCS - Digital Crossconnect System
A more detailed breakdown of a CO would look as follows:
(fiber)
| |_____| | | |
| /| | | _| |________|LFTB|____\ WORLD
| |____|/ |_____|DACS| _| | _| | |____| /
|COTIM| | /| |____| _| | _|DS3|
| | | \|________________|MUX|____|DSX|________| |
| |____|DSX|________________| | _| | |LFTB|_____\ WORLD
|_____| |___| |___| _|___| |____| /
Instead of the fiber shown in this drawing, digital radio or cable based
T1,
T1C, and T2 may be used in the interoffice plant.
Each piece of equipment in this arrangement must be capable of 64kb clear
channel signaling or it cannot be made available on an end-to-end basis.
For
service protection, the trunk paths between two end points are usually
spread over as wide a range of equipment as possible. Thus, providing 64kb
clear
channel capability for certain interoffice connections may involve updating
a significant amount of equipment in the central office.
From mkapor Wed Dec 11 12:17:32 1991
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Date: Wed, 11 Dec 1991 17:17:32 -0500
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From: Russ Nelson <nelson@cheetah.ece.clarkson.edu> (by way of mkapor@eff.org
(Mitch Kapor))
Subject: Tutorial on Telephone network architecture
> [Tim Gorman <71336.1270@compuserve.com> provides the following useful
> tutorial on ISDN in the telephone network. -MK]
Tim left off the subscriber end, perhaps because this is more common
knowledge. But I'll fill it in anyway...
Everyone knows that ISDN carries synchronous 2B+D, and that each B is
64Kbps packet or circuit switched, and the D is 16Kbps packet
switched. Synchronous means that the data is constantly flowing at
the specified rate. Most modems in use today use asynchronous
transmission, which means that each chunk of information has a
starting indication and an ending indication.
Packet switched means that the stream of bits is formatted
into packets, and each packet is transported as a unit. Circuit
switched means that the stream of bits goes from one end to another
without being interpreted by the switching equipment.
There are two different flavors of 2B+D: U and T. ANSI has defined
two different interfaces in the customer's premises, T (or S/T) and U.
The U interface connects directly to the switch over a 0 to 18,000 foot
loop, and uses one pair. The T interface connects to the U interface
through a signal converter called an NT1. It uses two pair (transmit and
receive) and runs at most 1,000 feet.
The U interface is electrically more sophisticated. The transmission
rate is 80Kbaud and each pair of bits is encoded into four different
voltage levels. This makes the data rate 160Kbps, plus it transmits
and receives in both directions at the same time. It does this by
knowing what it's sending, and subtracting that from what it's
receiving. Then it digitally filters the result. This is necessary
because the local loop to your premises may contain multiple changes
in impedance. That happens when your wire gauge changes, or you have
a tee connection. These impedance changes muddy the digital signal.
There can be only one device on the U interface, most probably an NT1.
The T interface, on the other hand, can be shared between multiple
devices. This is done because you can hang a telephone, a modem, and
a FAX machine off the same phone line. When a FAX machine calls you,
your FAX machine answers. When a modem calls you, your modem answers,
etc.
There are three concerns with ISDN:
o Powering
o Wiring
o Extensions
Powering
The current telephone network (POTS -- Plain Old Telephone Service
[seriously]) is powered by the central office. Ever notice that your
phone has a "REN"? That stands for Ringer Equivalence Number. It's
given in units of the standard telephone bell. Your central office
can ring about five of these bells. If the total of all your RENs is
over five, then your phone may not ring.
ISDN, on the other hand, uses no power from the central office. That seems
like an advantage, but what happens when you lose local power. The central
office still runs because it has its own batteries. But you can't make
calls unless you have your ISDN sets on a UPS.
Wiring
POTS phones can and have been wired willy-nilly, in a star configuration,
or bus. Because only two wires are necessary, sometimes only two wires
work.
ISDN, on the other hand, requires a single stretch of wire with terminators
on both ends, and it requires four wires.
Extensions
POTS sets can join into an existing phone call simply by going off hook.
Only one ISDN set can communicate on a B channel at a time. That means
that only the originating or receiving set can communicate. All the
other sets cannot transmit or receive.
--russ <nelson@clutx.clarkson.edu> I'm proud to be a humble Quaker.
Peace is not the absence of war. Peace is the presence of a system for
resolving conflicts before war becomes necessary. War never creates peace.
From mkapor Thu Dec 12 14:46:57 1991
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From: peterm@halcyon.com (Peter Marshall) (by way of mkapor@eff.org (Mitch Kapor))
Subject: Article on "The Argument Against ISDN"
...Let's set the mirrors aside and see what we really have with ISDN:
ISDN provides 64 kilobit digital, full-duplex data. It does so to any
other ISDN line when using a carrier that is fully digital, compatible
and offers the service.
ISDN provides point-to-point connections, similar to a telephone.
Connections can be established in a few seconds.
ISDN provides several enhanced features, such as calling line
identification and data privacy....
Telephone companies invariably fear new technology.... New technology
upsets rate structures. And new technology upsets *the natural order of
things.*
ISDN is a new technology.... ISDN represents competition to local
dialtone loops.... There are many questions. The traditional telco
response is simple: Charge a high enough price that these concerns
simply go away because of the profits generated....
implementation of ISDN has involved changing out central office lines.
Designing $1000 boxes for the customer end. It has meant converting the