Network Analysts and Consultants
"We Have the Experience"
ViewsLetter on Provisioning
21 Oct. 2002 #8
PUNCHDOWN TOOL MAY REACH ENDANGERED LIST
AS MATRIX AUTOMATES WIRES AT PHYSICAL LAYER
Used to be that the incidence of T-1 outages dropped sharply during the
lunch hour. It seems that the guy with the screwdriver and punchdown
tool, the craftsman, was using his buttset to find "unused" pairs on the
main distribution frame in the central office (CO). Of course his telephone
didn't notice digital traffic, so he'd cut off a T-1 leased line to provision
Fortunately, times have changed. Most physical (Layer 1) reconfiguration
of data circuits and digital voice channels now happens on the network of
Digital Access and Cross Connect Systems (DACS), controlled from a console
and keyboard. POTS lines are separate.
So how does a local loop of copper wire know which service it carries?
We still need the craftsman with a punchdown tool to set up the initial connection.
But automation is coming to this level, allowing the Operations and Support
System (OSS) to bring physical layer deployment under automated control.
The magic lies in an adaptation of an old protection switch from the days
of IBM's SNA on multidrop analog lines. Those lines were subject to
failure, as were front end processors that handled communications protocols,
and even entire mainframe computers--sites that handled real-time transaction
processing go to great lengths to keep the system running. A popular
technique was to provide duplicate hardware and backup lines. If anything
failed, a large matrix switch set up an alternate connection so business
Matrix switch technology was fundamentally simple: metallic contacts
between metallic wires. They were completely transparent to all signals
(one switch might handle analog modem signals as well as digital data streams).
To help rather than hinder reliability, the matrix switch became extremely
reliable--configuration changes didn't occur often, so they didn't wear out
and the basic relay contact was nearly bullet proof after 100 years of development.
REAL -WORLD JOB
Imagine a POTS subscriber orders Internet access from the Local Exchange
Carrier (LEC) based on Digital Subscriber Line (DSL) technology wihch will
share the local loop with POTS. The LEC has to reroute the wire pair
to a splitter, which separates the voice and data signals based on their
frequencies. From the splitter, two separate cables carry voice to the
old switch port and data to the DSL Access Multiplexer (DSLAM). Ignoring
the issues of IP-level provisioning (setting up account names, passwords,
procedures), there is a fair amount of work need to set up the cabling.
Into this CO scenario, insert that concept of "transparent, metallic-path
switching" that we saw in the data center. The goal is to feed all
the local loops into part of a matrix, the remainder of which connects to
all the input/output ports of the electronic hardware in the CO.
Now the POTS customer's copper line terminates on the matrix switch, not the
voice switch which is on "the other side" of the matrix. Moving a copper
pair to a splitter becomes a matter of modifying the switch's matrix (relay
contacts) to route the metallic path as needed. The port on the voice
switch connects in the same way to the other side of the splitter. You
can also see how the "data" port on the splitter goes to the DSLAM.
Are we there yet? No, but we're on the way.
Turnstone Systems (Santa Clara, CA: www.turnstone.com) has been
working on the problem for a while. Initially they focused their copper
automation solution on those loops that are used now (or are good candidates)
for DSL service. Their CX100 Copper CrossConnect, which provided a
way to remotely test subscriber lines and route users to spare ports on
the DSLAM, used relay technology similar to that deployed in existing matrix
The DSL application was an entry point for Turnstone to penetrate the
provider space with copper automation technology. Recently they've
expanded their product set to focus on other full scale CO applications,
where the number of subscriber lines is in the tens of thousands with a corresponding
number of ports on the hardware, such as splitters, DSLAMS, and voice switches.
In order to address new CO applications, Turnstone increased the size of
its switching capabilities, while extending the scope of its software to address
"one new application at a time," according to Eric Andrews, Turnstone's VP
Expanding beyond DSL, Turnstone's most recent focus has been on automating
the delivery and maintenance of Unbundled Network Elements (UNEs), used to
deliver POTS, DSL, ISDN, and special services. Turnstone's latest solution,
the MX500 (currently in live field trials), addresses the provisioning of
unbundled circuits to alternative carriers on a network-to-network basis.
The market for UNEs appears to be growing very strongly, with approximately
a 23% annual growth rate according to the FCC. In addition, existing
UNEs undergo a certain amount of churn, as the customers who choose CLECs
tend to change their minds, and the CLECs themselves have often disappeared.
Historically, service turn up and churn management has required a lot of
physical wiring changes, which is costly as it consumes a great deal of time
and human resources. The MX500 product is tailored to this problem,
providing remote switching capabilities to up to 2750 lines per rack.
As loop cutovers require switching between well-defined facility locations,
any-to-any switching functionality is not required in the UNE cutover application.
Going beyond UNE management, there are other applications that might require
any-to-any copper switching. Expanding a copper automation solution
to the "ideal" coverage of all loops and all ports within a CO is not an
easy task. As size and complexity grows exponentially when deploying
an any-to-any solution, the economics have historically not been viable for
addressing these types of applications with existing matrix switching technology.
Turnstone isn't ready to announce a new design, but hint there are emerging
ways to provide this functionality with reduced complexity and improved scalability
A copper switch is just a way to put on "wire nuts" by remote control.
So the nature of the control determines how a matrix fits into a carrier's
provision scheme. Turnstone is working with Telcordia (what was Bellcore
and before that a part of Bell Labs) to integrate copper automation into
Telcordia's OSS software. Previously, a NOC technician generated a paper
order for a craftsman to implement a wiring change. By combining Turnstone's
ONYX copper automation software with key Telcordia OSS components, these
processes can be completely automated in a flow through fashion.
Seeing Telcordia involved in physical layer or metallic provisioning automation
is encouraging. Telcordia is one of the leading suppliers of OSS software
to the major phone companies of this country and the world. If an OSS
upgrade (rather than a replacement) makes automation possible, automation
will be much easier.
Recall the "Access" portion of the DACS, mentioned above. In the
CO, this term most often has the special meaning of "connecting via metallic
path" to something with a test set. In the old days, craftspeople took
the test set around, attaching it to whatever point in the copper pair they
could reach. A DACS still needs to do this because some tests are in
the analog realm (impedance, balance, resistance; detecting loading
coils and bridged taps). Turnstone has built test equipment into its
matrix switches, eliminating the need to maintain mobile equipment.
Testing started with the specialized job of qualifying local loops for
DSL service. Later products perform spectrum analyses and other tests.
In all, a good start at a "virtual craftsman."
"Flanagan Consulting" and "ViewsLetter" are
Service Marks of W. A. Flanagan, Inc.
Updated: 11 June 2003