Intelligent SS7 or Stupid Networks
Why We Care
By Gary Kim
Going to the dentist for a root canal
might be preferable to sitting through a discussion of Signaling
System 7 (SS7). Nevertheless, we care about SS7 because it
enables many types of services related to call completion and
billing; little things like call forwarding, the ability to
change your local telephone carrier without changing your phone
number (local number portability), 800 service and debit and
credit card billing.
Still, network visionaries say the decade-long effort to
stimulate adoption of SS7-based "intelligent network"
and "advanced intelligent network" capabilities is
threatened by newer technologies based on Internet protocol (IP),
In the meantime, though, SS7 enables basic calling services
associated with the Integrated Services Digital Network (ISDN),
including Customer Local Access Signaling Services (CLASS). CLASS
includes services such as caller identification, calling name ID,
selective or priority ringing, call forwarding, call blocking,
call screening, repeat dialing, call trace and automatic
Carriers, resellers and agents who want their customers to use
any of today’s digital signal processor (DSP) technology for
voice prompts, for example, generally will rely on SS7 services.
Automated attendant functions are but one example. When a caller
gets a voice prompt suggesting he "push one for travel
within North America, push two for international travel, push
three to review your account, push four to hear the list of
options again," that’s an example of SS7-enabled
When a long distance carrier provides a voice prompt allowing
use of a prepaid calling card, credit card or
reversed/third-party billing option, that’s a use of the SS7
network. When a carrier wants to validate a calling number in
real time, that’s also a use of SS7.
When retailers or financial institutions want to verify or
activate a consumer credit card over the phone by using a call
center that can do a database lookup based on the home telephone
number, that’s SS7 in action.
So, we care about SS7 because it enables a major long distance
minute of use (MOU) distribution channel, namely credit and debit
cards. We also care about SS7 because without it, there will be
no effective competition in the burgeoning local calling markets,
Efficiency–not wasting valuable network transmission
resources–is the idea behind SS7. The concept is pretty simple:
Check a calling path before an actual voice circuit is created,
so the network isn’t tied up unnecessarily. In the perhaps dense
lexicon of SS7, databases (service control points, or SCPs) are
able to communicate with digital switches, polling them before
creating calling circuits. SS7 is, as its name implies, a
signaling system, a standard way of allowing all the network
databases and switches to exchange data. Multivendor equipment
interoperability, and the subsequent ability to lower equipment
and software costs, were other motivating forces.
Local number portability (LNP) is the reason. Recall that
telephone numbers are associated with particular switches and
physical locations. But as customers begin to move around,
associating a number with a place is an assumption that goes
away. Fundamentally, it is the same issue as 500, 800, 888 or 900
telephone numbers. The dialed number is not necessarily the
location a call is to be delivered.
As local carrier competition and the requirement for local
number portability become bigger factors, the signaling system
might have to start doing database lookups before completing
every call, since the network will not know in advance whether a
dialed number is to the place where a call is physically
delivered or only a call-forwarding number.
And that’s just for local portability within the same city or
rate center. What happens when a customer wants to port the
number on a regional, national or "galactic" basis,
muses David Nicol, vice president, product management, Olympia,
Wash.-based Illuminet. Wireless carriers have even more incentive
to use SS7-based networks, since their customers, by definition,
are mobile, and the telephone number is not associated with a
But advanced services, not just number portability, are part
of the attraction of SS7-enabled networks. SS7 plays a role in
over-the-air activation, which helps wireless carriers reduce
administrative cost. SS7 also helps with customer authentication,
which cuts fraud losses. Revenue upside also is an attraction.
Consider voice-activated dialing, for example, says Faye
Vorick, Motorola Cellular Infrastructure Group manager. Say a
wireless carrier serves 100,000 customers. Then assume 5,000
users, or 5 percent of the base, can be induced to spend $3.50 a
month for this feature. That boosts monthly revenue $17,500 a
month, says Vorick.
An even bigger boost comes when customers get free voice mail,
because customers tend to use more airtime when checking
messages, and probably will boost calling time by returning some
of the messages using the wireless phone, Vorick suggests. Assume
10 percent of these 100,000 wireless carrier’s customers sign up
for free voice mail service, and assume they use an average
additional 40 minutes of airtime each month at 28 cents a minute.
That boosts revenue $11.20 per account or $112,000 a month.
SS7 also plays a key role in wireless network fraud control
operations, says Robert Fike, Irvine, Calif.-based Subscriber
Computing Inc. executive. The U.S. wireless industry suffered an
estimated $950 million fraud loss in 1996, for example, Fike
says. SS7 helps because it enables real-time call control based
on an individual’s typical calling pattern, as well as a
validation at the time of call origination or termination. Such
validation procedures can be triggered by initiation of an
international call, a call from a known "fraud hot"
location, or when the calling pattern is judged to be abnormal.
All said, has SS7 actually led to an explosion of carrier
Not really, most observers say. Says Micaela Giuhat, senior
product marketing manager, IEX Corp., Dallas, who recently came
back to SS7 work after a five-year absence, "the same issues
still are being discussed."
Indeed, there are disquieting signs that technology may be
poised to race past the advanced intelligent network. Kevin
Keough, marketing chief, I-NET, Bethesda, Md., says the movement
of device intelligence towards the periphery suggests a different
model. "SS7 functionality should be embedded in people’s PCs
(personal computers), just like Microsoft’s Excel
spreadsheet," Keough suggests.
Giuhat agrees. "Technology evolution has spread network
intelligence from the network core to the edges," she says.
In that case, the "network becomes a ‘pipe’ retaining only
the basic routing function." In the future, she suggests, IP
networks will have the rich functionality once envisioned for the
advanced intelligent network, while the public wide area network
remains the carrier of last resort. In essence, the public
telephone network becomes the "poor man’s network."
This is a somewhat startling prediction, though hardly an
unusual sentiment. In effect, executives are starting to suggest
that the vaunted intelligent network will be superseded by an
essentially dumber network in which services, applications,
functionality and control are directed from the edge, not the
core of the network.
Fred Signeur, president, SoneTech, Bedford, N.H., says the SS7
function can be provided over the same IP platform Giuhat and
others say is becoming the high-functionality network. Robert
Wienski, Illuminet director of intelligent network services,
thinks that is possible.
This is no idle technological speculation. If SS7 functions
can be provided over IP networks, then IP networks can provide
all of the expected calling features once believed to be the
province of the advanced intelligent telephone network.
The Stupid Network
Such heretical thoughts seem to be spreading. In a surprising
June 1997 post to the World Wide Web, AT&T Laboratories
researcher David Isenberg, who had cleared his post with AT&T
before letting it fly, talked about the "Rise of the Stupid
Network" (e-mail him at email@example.com to
get a copy). In a nutshell, Isenberg says a new–and
different–public network is emerging, one unconstrained by
bandwidth scarcity or expensive computing resources.
What SS7 Enables
Blasting "obsolete assumptions," Isenberg says the
intelligent network, designed to automate operations and ensure
equipment interoperability, faces a new challenge from the stupid
Indeed, he says the intelligent network is being superseded by
a stupid network, with nothing but dumb transport in the middle,
and intelligent user-controlled endpoints. The model is the
In business jargon, eliminating the middleman is known as
"disintermediation." In essence, the Internet
disintermediates local and long distance companies by passing
call completion tasks to end-user devices and IP addresses
assigned to those devices.
Indeed, in the next generation of IP (IPv6), real-time,
two-way voice conversations will be feasible.
In the future,
The change is quite significant. Where SS7 explicitly assumes
that circuits are expensive resources, IP networks essentially
assume there are no bandwidth or transmission limitations, at
least for narrowband traffic. Wherein the SS7 model the network
tells the data where to go, IP networks essentially use a
nondirective approach in which the data itself carries the
information required to get it to its destination. That’s one
reason why major equipment suppliers now are so bullish about
voice over IP technology for facsimile and voice services,
especially for international and intrabusiness applications.
For now, everybody in the telecom business cares about SS7
because everybody relies on the call processing functions it
provides. Longer term, many competitors may care less about SS7,
if only because other alternatives may emerge.