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TUCoPS :: Phreaking Technical System Info :: 555tech.txt

555 Exchange service expansion





TABLE OF CONTENTS


1.0	INTRODUCTION	2
	1.1	Purpose of This Document	2
	1.2	Background	2

2.0	TECHNICAL SERVICE INTERCONNECTION REQUIREMENTS	2
	2.1	Dialing Arrangements	3
	2.2	Digit Analysis and Translations	3
	2.3	Translations	4
	2.4	Routing	5
	2.5	Signaling Arrangements	5

3.0	TECHNICAL SERVICE INTERCONNECTION ARCHITECTURES	6
	3.1	Translations, Routing and Signaling Examples	6
	3.2	Potential Architectural Arrangements	8
        3.3     Potential 555 Technical Service Interconnection
                Arrangements (TABLE 1)  10

4.0	BLOCKING CONSIDERATIONS	11

5.0	BILLING AND ORDERING CONSIDERATIONS	11
	5.1	Ordering	11
	5.2	Billing	11

6.0	NETWORK CONSIDERATIONS	12
	6.1	Availability of Digit Analysis and Translation	12
	6.2	Signaling Protocol	13
	6.3	Calls Routed to the Designated Carriers' Network	13
	6.4	Calls Routed to the Presubscribed Interexchange Carrier (PIC)	13
	6.5	Additional Considerations	14

7.0	Glossary	14
	7.1	Definitions	14
	7.2	Acronyms	18

APPENDIX A	
	History	19
	555 Network Today	19
	Current Regulatory Considerations	20

APPENDIX B        
	Listing of Grandfathered Numbers	21
	
1.0	INTRODUCTION

1.1	Purpose of This Document

This document identifies potential technical service interconnection
arrangements and dialing plans that could be used by providers of services
using 555 line numbers.  This document complements the existing 555 NXX
Assignment Guidelines, (INC94-0429-002 Rev. 1).  For each potential
technical service interconnection arrangement, the elements required to
provide services using 555 line numbers are described.  The need for
transferring end-user billing and dialing information to the designated
carrier or the service provider is detailed to the extent possible for each
potential technical service interconnection arrangement.  Several basic
national uniform technical service interconnection arrangements will allow
both access providers and information providers to plan more effectively
the ubiquitous deployment of services.  Any such changes, including
modifications or additions to the document, will be made under the
direction of the ICCF (Industry Carriers Compatibility Forum).

The technical service interconnection arrangements described in the
document should be considered the product of industry consensus.  The
decision whether to implement any of these arrangements, and when any such
arrangements may be deployed, is likely to be based on business
opportunities and regulatory factors and may vary accordingly.  Moreover,
nothing in this document precludes the use of alternative arrangements
which may include some or none of the features described.

1.2	Background

Previously, the use of "555" numbers and the network arrangement used to
route and complete "555" calls have been associated primarily with the
support of DA (Directory Assistance) services.  The assignment guidelines
for 555 line numbers (INC 94-0429-002 Rev 1.) allow these numbering
resources to be used not only for DA services, but for a broad range of
other services.  The service arrangements described in this document are
intended to support both DA and other services.

2.0	TECHNICAL SERVICE INTERCONNECTION REQUIREMENTS

Several network technical requirements must be satisfied in order to
complete calls dialed with "555" numbers.  These requirements reflect the
need to:

        a)      accommodate a given dialing arrangement,
	b)	appropriately translate the dialed number,
	c)	route the call to the access customer or service provider,
        d)      provide that customer or provider the necessary
                call-related information to support the desired service,
        e)      record the necessary call detail,
        f)      ultimately bill the call and
	g)	provide blocking if appropriate

2.1	Dialing Arrangements

The "555" numbers may be dialed using either 7 or 10 digits depending on
service arrangements and the local dialing plan.  "555" numbers assigned on
a national basis could be dialed using only 7 digits from any location in
an NPA (Numbering Plan Area) in which appropriate technical service
interconnection arrangements have been ordered and deployed.  Any national
or non-national number could be dialed using 7 digits, if dialed from
within the NPA(s) in which it is activated.  If a national or non-national
555 number is dialed from outside the area code in which it is activated,
it will be necessary to dial 10 digits.  Accordingly, access networks
should be able to accommodate 10 digit dialed 555 as well as 7 digit dialed
555 numbers, if either 7 digit dialing of 555 national numbers or 7 digit
dialing of non-national numbers within the home NPA is permitted.

2.2	Digit Analysis and Translation

The term digit analysis and the term translation are frequently used in
this document.  Although these terms are common within the
telecommunications industry, they are often subject to somewhat differing
interpretation and meaning.  Within the description of 555 technical
interconnection arrangements, digit analysis is intended to imply the
examination of part of the digit string (typically 3 or 6 digits) in order
to identify the type of call and any subsequent activity which must be
performed.  Translation is considered to be that action necessary to route
the call, and could include the literal translation of a dialed number to a
different (routable) number, or simply the selection of a route based on
the dialed number.

For example, in 800 access, an end office performs a 3 digit analysis to
identify the call as 800, and then typically launches a query to an
external database where a 10 digit translation of the dialed 800 number
provides a 10 digit routable number or a CIC (Carrier Identification Code)
(or both), which is used to route the call.  If the dialed 800 number is
forwarded to the 800 service provider, an additional translation in that
provider's network is necessary for call completion.

The analogy to the 555 environment is clear.  A 3 or 6 digit analysis of
the dialed number is necessary to recognize the "555" call.  Subsequent
call processing will likely include a 7 or 10 digit translation for proper
call routing.

2.3	Translations

A 7 or 10 digit analysis of the dialed number is performed in order to
determine the carrier or 555 assignee to which the call should be routed.
After this analysis is performed, the dialed number is translated to a
routable number or to a carrier identification code designated for a
particular 555 number via a CIC.  The network in which this translation is
performed affects the technical service connection arrangement.  There are
three categories of networks where translations could be performed:
originating, terminating and intermediate.  Originating network
translation(s) are those that occur in the network from which the call
originates.  Terminating network translation(s) are those that occur in the
network in which the call is completed to the location designated by the
555 number assignee.  Intermediate network translation(s) are those that
occur in a network in the call path that is neither the originating nor
terminating network.

2.3.1	Originating Network Translation

If the translation is to be performed in the originating service provider's
network, the capability to perform this function could be resident in each
end office, or it could be provided at a point of concentration, either an
access tandem or operator tandem switch.  In addition, the translation
could be realized through data stored in an external database and obtained
via a database query from appropriately equipped (SSP [Service Switching
Point]) switches.

2.3.2	Terminating Network Translation

If the translation is to be performed in the terminating network, the
translation would most likely be provided at one point of concentration as
described in the LERG (Local Exchange Routing Guide), either an access
tandem or operator tandem switch.  This capability would find application
when a "555" call is routed by the originating service provider to the PIC
(Presubscribed Interexchange Carrier).  If the point of concentration
processes terminating traffic to multiple NPA's, it would require that the
full ten digit 555 number be forwarded to the terminating network by any
intermediate transport provider.  The terminating network would then
provide the necessary translation and complete the call to the location
designated by the 555 number assignee.


2.3.3	Intermediate Network Translations

The translation could also be performed in an intermediate network when the
originating network routes the call to the intermediate network based upon
the PIC of the calling line.  This arrangement would require that the full
ten digit 555 number be dialed and that the full 10 digit number be
delivered to the intermediate network.

In another case, where an activated seven digit number is dialed, a routing
analysis and translation would be required in the originating network to
determine and route the call to the carrier designated for a particular 555
number.  In this case, another analysis and translation would be required
in the intermediate network to determine the routable number.

2.4	Routing

In the access network, a 555 call is routed to a location designated by the 555 number assignee such as:
the point of presence (POP) of a specific interexchange carrier;
the POP of the carrier presubscribed to the calling line (the "PIC")
a termination within the local network.

When multiple exchange providers exist in local calling areas, the call
could be routed to an interconnection point of another local service
provider by mutual agreement of the affected parties.

The network capability described above can support the routing of calls
dialed with "555" numbers as both an exchange access service as well as a
local exchange service.

2.5 	Signaling Arrangements

Signaling could be provided in the form of Multi-Frequency (MF) and/or
Signaling System 7 (SS7).  These Signaling types can be utilized for the
following applications; exchange service, operator services, access
services, etc.  (See Section 3 and Figure 3-1).  Potential features and
interface options for the signaling interfaces are summarized in Section
3.3, Table 1.  Calls routed to either an interexchange carrier or to a
carrier designated by the 555 number assignee may require that the
originating network provide information needed for billing and routing to
the intermediate carrier who will then provide the same information to the
terminating network.

3.0	TECHNICAL SERVICE INTERCONNECTION ARCHITECTURES

This section describes access and exchange service architectures that could
be used for 555 services.  The service arrangements are categorized based
upon the following network functions:

1.translations of the dialed number
2.the routing of the call
3.the type of signaling

These functions and their relationships are illustrated in Figure 3-1.  The
translation, routing, billing, blocking, and signaling characteristics are
summarized in Section 3.3, Table 1.

3.1	Translations, Routing and Signaling Examples

Using Figure 3-1 as a reference, consider a local service example in which
a customer dials a seven digit 555 number.  The originating network could
perform a seven digit analysis and translation of the 555 number and
determines that the call should be completed within the same originating
network.  (See S1, S2 or S3 in Figure 3-1)  The call would be delivered to
the location of the 555 number holder on an intraLATA basis to a line side
termination.  (See S2 in Figure 3-1)

In the intermediate example, two potential situations could exist.  In the
first case, a caller dials a 10 digit 555 number with an NPA in a foreign
LATA (Local Access Transport Area).  The originating switch could route the
call to the interexchange carrier identified by the PIC of the originating
subscriber's line using a FG D (Feature Group D) interface (S-1).  The
PIC'd interexchange carrier could then analyze and translate the 555 number
and route the call appropriately.

In the second case, a caller could dial either a 7 or 10 digit 555 number.
The originating switch could perform digit analysis and translations of the
555 line number to determine the designated carrier (S1 in Figure 3-1)
selected by the 555 assignee and route the call to that designated carrier.
The designated carrier could then perform digit analysis and translate the
555 number and route the call appropriately.

In a terminating example, a caller dials a 10 digit 555 number that is
intended for a foreign NPA.  The originating switch could route the call to
the interexchange carrier identified by the PIC of the subscriber's line
(S1 in Figure 3-1) using FG D interface.  Thus far, this example is
originating translation.  Based upon the 10 digit dialed number, the
interexchange carrier could terminate the call to the LEC (Local Exchange
Carrier) tandem specified in the LERG.  (This is the terminating network in
Figure 3-1).  The terminating LEC tandem could translate the seven digit
555 line number to a number in the terminating LATA to an exchange trunk
interface (S2).  Thus, translations would have been performed in the
terminating LATA.

 3.2	Potential Architectural Arrangements

The translations, routing and signaling variations from Figure 3-1 are
further illustrated in Figure 3-2.  The left side of Figure 3-2 illustrates
calls originated and terminated in the same LATA.  The right side
illustrates terminating calls from an interexchange carrier that were
originated in another LATA.

Reference is made to a database in Figure 3-2 to perform the necessary
screening and translations on the 555 line number to determine the proper
carrier or 555 assignee interface.  The use of a database and its location
is the decision of the individual network provider(s).

References are also made to 555 calls from wireless stations via a MTSO
(Mobile Telephone Switching Office).  However, such 555 technical
interconnection arrangements are not detailed in this document.

The signaling interfaces between switching entities in Figure 3-2 indicate
options that are labeled as follows:

	Originating	Terminating
From	To	Signaling	From	To	Signaling
MTSO* 	EO	Type 1 or 2B	IC	AT/OS	D (Terminating)
MTSO*	LT/AT/OS	Type2A/Type2D	AT/OS	SP	ET
MTSO	IC	D, O, DC (Subject	EO	SP	EL
		(to negotiation)
AT/OS	IC or SP	D, O	EO	SP	ET
EO	IC or SP	D, O	IC	SP	DC (subject to 
					negotiation)
EO	SP	EL
EO	SP	ET

Options
Dialing:  7 or 10 digit
Translations:  originating or terminating
Routing:  PIC, designated carrier or service provider
Signaling Interface:  FG D, OSS, Type1,2A,2B, 2D or Exchange

Abbreviations
D = Feature Group D		DC = Direct Connection	
O = Operator Services Signaling	MTSO = Mobile Telephone Switching Office
EL = Exchange Line Side		AT = Access Tandem
ET = Exchange Trunk Side		EO = End Office
LT = Local Tandem		IC = Interexchange Carrier

 3.3 	Potential 555 Technical Service Arrangements (Table 1)

Table 1 summarizes potential technical service interconnection arrangements
that could be considered for the implementation of services using the 555
number resource.  Although the Table lists several arrangements, it may not
be inclusive of all possible applications; it is included to provide the
reader with examples of potential service arrangements.

The service types identified in Column I. indicate whether the application
is for a DA-like service or information service. Column II. shows the
party(ies) who may be billed for each of the service applications.  The
potential need for end user blocking is shown in column III.  Columns IV.
and V indicate what both the dialing plan and the routing translations
could be on either a 7 or 10 digit basis.  Column VI. describes the call
routing which might be to a local termination (e.g., intraLATA service) or
to an interexchange carrier which could be either the PIC of the
originating caller or the carrier designated by the 555 assignee.  Possible
signaling/protocol arrangements that might be available for each
application are depicted in Column VII.


TABLE 1 - Potential Technical Service Interconnection Arrangements

       I.

 Service	      II.

Billed to	      III.

Blocking	    IV.
Dialing Plan	          V.   Translations Note 2	       VI.

Routing	        VII.
Signaling/
Protocol	
DA-like	Calling Party

555 Assignee	May be required.

Note 1	7/10D	7/10D	Local Term

PIC

Designated Carrier	MF, SS7/

FG D
OS
Type 1
Type 2	
800-like	555 Assignee	No	7/10D	7/10D	Local Term

PIC

Designated Carrier	MF, SS7/

Exchange
FG D
Type 1
Type 2	
900/976-like	Calling Party

555 Assignee	May be required.

Note 1	7/10D	7/10D	Local Term

PIC

Designated Carrier	MF, SS7/

Exchange
FG D
Type 1
Type 2	

Note 1  Blocking may be required to meet regulatory requirements, depending
        on the type of service.

Note 2  The translation of the dialed number to a different (routable)
        number could be performed in the originating, intermediate or
        terminating network.

4.0	BLOCKING CONSIDERATIONS

Blocking will be implemented according to jurisdictional
rules/requirements.  Additional blocking requirements by an end user, 555
assignee, or network provider may be provided on an individual case basis.

5.0	BILLING AND ORDERING CONSIDERATIONS

Although billing and ordering arrangements are outside the scope of this
document, some high level ordering and billing considerations are included
in this section.

5.1	Ordering

Ordering technical service interconnection arrangements is expected to be a
process that will involve local service providers, long distance providers
and 555 assignees.  It is expected that a 555 assignee who wishes to order
service will do so from an exchange/access provider.  This may be line or
trunk side depending on the signaling capabilities needed and volume of
calls.  Because of the variety of potential technical service
interconnection arrangements, it is expected that local exchange providers
will develop appropriate ordering arrangements.  Additionally, if the 555
assignee intends to provide the 555 service across jurisdictional
boundaries, some arrangement may need to be made with an interexchange
carrier.  For these reasons, it is expected that the 555 assignee will
coordinate efforts to order these services.

The assignment of a 555 number does not initiate the implementation of any
technical service interconnection arrangement that may be necessary to
complete 555 calls.  Rather, it is expected that access service requests
(ASRs) or an exchange service order, if the service is a local application,
will be initiated by the 555 assignee, or their agents, in all locations in
which the 555 assignee wishes to receive calls dialed with its assigned
number.

5.2	Billing

It is expected that technical service interconnection arrangements will
have the functionality needed to perform appropriate AMA recording to
support billing.  Charging scenarios may include calling party pays, called
party pays or a combination thereof and appropriate access/exchange
transport charges.



6.0	NETWORK CONSIDERATIONS

Network service capabilities required to route 555 calls  presently exist
for some, but not all of the technical service interconnection arrangements
described in Section 3.  Basic to the provision of these arrangements is
the use of 7 or 10 digit analysis of the dialed 555 number and associated
translation to route the call to the designated carrier or the location
designated by the 555 assignee.  Depending upon the specific technical
service interconnection arrangement desired, this translation capability
could be provided in either the originating, intermediate or terminating
network(s).

6.1	Availability of Digit Analysis and Translation

Both, an exchange service arrangement used to complete 555 calls on a local
basis, and an exchange access arrangement used to route a 555 call to an
interexchange carrier other than the PIC, would require 7 or 10 digit
translation provided either internal to a switch or via an external data
base.  The capability for the necessary 7 or 10 digit translation could be
available in each end office or the call could be routed to a point of
concentration, e.g.,  a tandem switch  where the translation could be
performed.

Although switch based 7 or 10 digit translation is possible, this
methodology requires additional switch memory and may be difficult to
implement in some networks.  Alternatively, the necessary translation could
be performed using IN or AIN features, together with an external database.
Specific 3 digit ("555") or 6 digit "NPA-555") triggers would initiate
queries to a database where routing information associated with specific
dialed (7 or 10 digit) 555 numbers would be retrieved and provided to the
network switch.  Although IN and AIN capabilities are increasingly
available in some local exchange and interexchange carrier networks, they
are not yet ubiquitous.

As explained in Section 2.1, digit analysis is required to identify the 555
call so that the necessary call processing can be provided.  Specifically,
3 digit analysis (555) is necessary if the "555" call is dialed with 7
digits and 6 digit analysis (NPA-555) may be required if the call is dialed
as a 10 digit call.  This 3 or 6 digit analysis is required in each and
every end office, regardless of whether translation is initiated in the end
office, or performed in a tandem switch.

Although six digit analysis is available in most end offices, it is
typically used only for Home NPA (HNPA) calls, or, at most, for calls
dialed with the HNPA and the few NPAs adjacent to the HNPA.  Calls dialed
with a foreign NPA (FNPA, [e.g., 1+ NPA 555-XXXX]) are subject to three
digit analysis which is only sufficient to identify the call as interLATA
and route the call to the PIC.  Accordingly, in order to route calls dialed
with an FNPA [e.g., (FNPA) 555-XXXX] to a carrier other than the PIC, six
digit anlaysis for calls dialed with any NPA (i.e., both HNPA and FNPA
alike) would be required.3 

If calls are dialed using seven digits (555-XXXX), the three digit analysis
currently performed in end offices would be sufficient to recognize the 555
call and initiate the necessary call processing or route the call to a
tandem switch

6.2	Signaling Protocol

It appears that access customers and transport providers may find it
desirable to receive the dialed number and ANI in the signaling information
existing in FG D signaling protocol.  Today, FG D signaling protocol is
provided in access connections when calls are routed to the PIC of the
calling line or the carrier identified by Carrier Access Code
(10XXX/101XXXX) dialing.  In addition, FG D signaling protocol is provided
on SAC dialed calls (e.g., 500, 800, 900) where the identity of the access
customer is derived from the dialed number.  The use of FG D protocol for
555 calls would allow routing based upon information derived from the
dialed digits.  Where both the dialed number and ANI are not desired or
available, other types of signaling protocol could be utilized for routing
and billing.

FG D  signaling is typically not available with (non-access) exchange
signaling.  Exchange signaling may be either MF or SS7 signaling and may
not include ANI.

6.3	Calls Routed to the Designated Carrier's Network

It is assumed that calls forwarded to a designated carrier could include,
the dialed 555 number.  Accordingly, the designated carrier could be
required to perform an additional 7 or 10 digit analysis and translation to
determine the destination of the call; that is, the location designated by
the 555 assignee.  In some cases the location of the 555 assignee will be
directly connected to the designated carrier's network.  Alternatively, if
there were no direct connection, the designated carrier could translate the
dialed 555 number to a routable number and complete the call via a
terminating network using terminating switched access.

6.4	Calls Routed to the Presubscribed Interexchange Carrier (PIC)

Existing capabilities within the originating network would allow interLATA
555 calls to continue to be forwarded to the PIC of the calling line or the
carrier designated by Carrier Access Code (10XXX/101XXXX) dialing, using FG
D signaling protocol.  With this arrangement, the PIC may have the
information necessary to route the call to the location designated by the
555 assignee, or the PIC could route the call to a designated switch in the
terminating network.  That switch may have the information necessary to
route the call to a location designated by the 555 assignee.

6.5	Additional Considerations

In areas where 555 service is offered, any arrangements currently employed
by carriers which only allows calls to (NPA) 555-1212 and blocks all other
(NPA) 555-XXXX calls to Directory Assistance, or routes all NPA 555-XXXX
calls to DA, regardless of the "555" line number dialed, will need to be
removed if completion of calls to other 555 numbers is desired.  Finally it
should be recognized that any implementation of routing for 555 calls must
retain the current disposition of calls dialed (1) + (NPA) 555-1212.  These
calls will continue to be routed to the originating service provider, PIC
of the calling line or the (10XXX/101XXXX) designated carrier.

It should be further recognized that support of multiple technical service
interconnection arrangements for 555 could have extensive technical network
impacts and may not be practical or feasible for all network providers.

7.0	GLOSSARY

This section includes a glossary of terms and acronyms used in this
document.

7.1	Definitions

555 Assignee -  the entity to whom a 555 number has been assigned.

Access Provider - Any Local Exchange Carrier who provides network
interconnection arrangements to permit Access Customers to originate and/or
terminate telecommunications in the areas in which the Local Exchange
Carrier offers telecommunications services.

Advanced Intelligent Network (AIN) - A service-independent architecture
which allow its service provider to create/or modify telecommunications
services.

Automatic Number Identification (ANI) - The automatic identification of the
calling station.  The ANI normally consists of the calling party's billing
number.

Carrier Identification Code (CIC) - a numeric code which is currently used
to identify an customer who purchased Feature Group B and/or Feature Group
D access services.

Called Party Pays - A service for which the end user receives and pays for
call.

Calling Party Pays - A service for which the end user originates and pays
for a call.

Designated Carrier - The carrier selected by the 555 assignee.  The
Designated Carrier is determined via 7 or 10 digit translation of the
dialed number.

Directory Assistance (DA) - A service providing the listed telephone number
for a given name and address.

Directory Assistance Call Completion (DACC) - After the listed telephone
number has been obtained, DACC is a service that permits a call to be
completed to the requested number, typically at the calling party's option
for an additional charge.

Exchange Access Services - Exchange access is a service provided by LECs to
interconnecting entities (such as interexchange carriers) in the areas in
which  the LECs offer telecommunication services.

Foreign NPA (FNPA) - Any other NPA outside the geographic NPA from which a
call originates.

Home NPA  (HNPA) - The geographic NPA from which a call originates.

Interexchange Carrier (IC) - A common carrier that provides services to the
public between local exchanges on an intraLATA basis in compliance with
local or Federal regulatory requirements and that is not an end user of the
services provided.

Industry Carriers Compatibility Forum (ICCF) - An open forum under the
auspices of the Carrier Liaison Committee to encourage telecommunication
entities to discuss and resolve, on a voluntary basis, national technical
issues associated with telecommunications network interconnection, and the
issues associated with the assignment and use of NANP/World Zone 1
numbering resources.

Industry Numbering Committee (INC) - A standing committee of the Industry
Carriers Compatibility Forum (ICCF) that provides an open forum to address
and resolve industry-wide issues associated with the planning,
administration, allocation, assignment and use of numbering resources and
related dialing considerations for public telecommunications within the
North American Numbering Plan (NANP) area.

Intermediate Network - Any interconnecting network (s) between the
originating network and terminating network.

Local Access and Transport Area (LATA) - A geographic area within which the
RBOCs and GTE may offer services.

Local Exchange Routing Guide(LERG) -A document that contains local routing
data reflecting the current network configuration and scheduled network
changes for all entities originating or terminating PSTN calls with the
NANP excluding Canada.

National 555 Number - A national number is a unique line number in the 555
NXX assigned to an entity for use in all or most of the geographic NPAs in
World Zone 1.  A number will be designated as a national number if it is to
be used in at least 30% of all NPAs or states or provinces in World Zone 1.
National numbers cannot be assigned by the Administrator to any other
entity.

NANP (North American Numbering Plan) - A numbering architecture in which
stations in the NANP area are identified by a unique ten-digit address
consisting of a three-digit NPA code, a three-digit central office code of
the form NNX/NXX, and a four-digit line number of the form XXXX where N
represents the digits 2-9 and X represents any digit 0-9.

NANP area (formerly known as World Zone 1) - Currently consists of United
States, Bermuda, Canada and some Caribbean administrations.

Non-national 555 Number - A non-national number is a line number in the 555
NXX assigned to an entity for use in a specific geographic area or areas
(NPAs, states, or provinces).  A number will be designated non-national if
it is to be used in fewer than 30% of NPAs or states or provinces.
Non-national numbers are available for assignment to multiple entities,
assuming those entities wish to use the non-national number in different
geographic NPAs.

Numbering Plan Area (NPA) - A 3-digit code, also called area code,  that
occupies the A, B, and C positions in the 10-digit NANP format .  NPAs are
of the form NXX, where N represent the digit 2-9 and X represents any digit
0-9.   In the NANP, NPAs are classified as either geographic or
non-geographic.

Originating Network - the network from which the end user obtains access to
the Public Switched Telecommunication Network (PSTN).

Pay-Per-Call Service - (The definition of pay-per-call service is extracted
from the TDDRA of 1992 Public Law 192-556, 47USC 228.)

(1) The term 'pay-per-call services' means any service --
A)in which any person provides or supports to provide--
II.Audio information or audio entertainment produced or packaged by such person;
III.access to simultaneous voice conversation service; or
IV.any service, including the provision of a product, the charges for which
   are assessed on the basis of the completion of the call;

                B)      For which the caller pays a per-call or
                        per-time-interval charge that is greater than, or
                        in addition to, the charge for transmission of the
                        call; and
                C)      which is accessed through use of 900 telephone
                        number or other prefix or area code designated by
                        the Commission....

(2) Such term does not include directory services provided by a common
carrier or its affiliate or by a local exchange carrier or its affiliate or
any service the charge for which is tariffed, or any service for which
users are assessed charges only after entering into a presubscription or
comparable arrangement with the provider of this service.

Presubscribed Inter LATA Carrier (PIC) - the carrier selected by the
customer if they wish to be presubscribed to an IC rather than selecting
the IC on every interLATA call.  The PIC is also frequently referred to as
the presubscribed IC.  In the context of this document PIC is also used as
the Presubscribed IntraLATA Carrier.

Plain Old Telephone Service (POTS) - POTS Plain Old (POTS) is a term used
to refer to lines connected to a local switching system that have basic
service capability.  Such lines are not identified within a closed user
group such as centrex or connected to Customer Premises Equipment, i.e.,
PBX.

Service Switching Points (SSP) - A network element that initiates a
dialogue with a database(s) in which the logic for the requested service
resides.

Service Provider (SP) - Any entity that is authorized, as appropriate, by
local government, state, federal, or other governmental authorities within
the NANP area to provide telecommunications service to the public.

Signaling System 7 (SS7) -  An international standard, general purpose CCS
(Common Channel Signaling) protocol.

Terminating Network - The network that delivers the call directly to the
service provider.

Trigger - An intelligent network switch functionality that allows
suspension of call processing in order to query an external database to
obtain additional information, e.g., routing or billing information.  An
example of one type trigger is analysis of the dialed digits, i.e., either
3 digits, 6 digits or 10 digits.

7.2	Acronyms

AIN (Advanced Intelligent Network)
ANI (Automatic Number Identification)
ANI II (Automatic Number Identification Information Integers)
ASR (Access Service Request)
AT (Access Tandem)
CIC (Carrier Identification Code)
DA (Directory Assistance)
DACC (Directory Assistance with Call Completion)
EL (Exchange Service Line Side)
ET (Exchange Service Trunk Side)
EC (Exchange Carrier)
EO (End Office)
FNPA (Foreign NPA)
HNPA (Home NPA)
IC (Interexchange Carrier)
ICCF (Industry Carriers Compatibility Forum)
IN (Intelligent Network)
INC (Industry Numbering Committee)
ITC (Independent Telephone Company)
LATA (Local Access and Transport Area)
LEC (Local Exchange Carrier)
LERG (Local Exchange Routing Guide)
MF (Multi Frequency)
MSC (Mobile Switching Center)
MTSO (Mobile Telephone Switching Office)
NANP (North American Numbering Plan)
NPA (Numbering Plan Area)
OS (Operator Switch)
PIC (Presubscribed Interexchange Carrier)
POP (Point Of Presence)
SAC (Service Access Code)
SP (Service Provider)
SSP (Service Switching Points)
SS7 (Signaling System 7)
APPENDIX A

History

Historically, the 555 line number range has been associated primarily with
Directory Assistance (DA) and the use of fictitious numbers by the
advertising and entertainment industries.  The Industry examined the
feasibility of a broader use of this resource.  In December 1992, industry
consensus was reached that the use of 555 numbers could meet an industry
need for providing different types of public information services.

In April of 1994, the Industry approved the 555 NXX Assignment Guidelines
(INC 94-0429-002).  The 555 NXX Assignment Guidelines apply to the use of
555 numbers for the provisioning of information services but may include a
broad range of existing and future services as well.  The North American
Numbering Plan Administration (NANPA) began accepting applications for 555
line numbers on June 17, 1994.  Those numbers became available for
assignment beginning July 8, 1994.  However, a set of numbers was
grandfathered for existing applications (See Appendix B).

555 Network Today

Today, the 555 NXX is used almost exclusively for the provision of Local
Exchange Carrier (LEC) Listing Retrieval Services, e.g. Directory
Assistance (DA).  Depending upon local dialing patterns, some originating
callers dial (1) + (HNPA) + 555-1212, and others dial 555-1212.  In most
cases, the end office performs digit translation only to the NXX level and
routes the call to the Operator Switch/Access Tandem (OS/AT).  Billing
recording is done at the end office and Operator Services Signaling (OSS)
is not required.  Calls from some Independent Telephone Company (ITC)
customers are routed to an OS/AT of another LEC for the provision of basic
DA.

From equal access end offices, if a customer dials an interLATA (1) + NPA +
555-1212, the end office performs three or six digit translation and the
call is routed to the customer's Presubscribed Interexchange Carrier (PIC)
like any other InterLATA call using FG D signaling.  The Interexchange
Carrier (IC) will route the call using the NPA-NXX and deliver the call to
the appropriate terminating Access Tandem (AT) or OS as specified in the
LERG.  The IC performs the recording by using the Automatic Number
Identification (ANI) information provided via the FG D signaling.

After an operator has retrieved listing information, Directory Assistance
with Call Completion (DACC), where it is available, permits a call to be
completed to the requested number typically at the customer's option for an
additional charge.  In order for the OS to perform the appropriate rating
and billing for the second leg of the call, OSS is required between the
originating end office and the OS.  OSS permits forwarding the ANI of the
calling party to the OS for billing recording purposes.  The DA traffic
from the end office to the OS could be routed on a separate trunk group or
could be combined with other operator traffic, e.g. 0-, 0+.

Some LECs have the ability to provide DACC on DA calls originating from
cellular carriers.  A dedicated trunk group using FG D signaling between
the Mobile Switching Center (MSC) and the OS is required.  DACC is not
currently provided on DA calls terminating from an IC.

Current Regulatory Considerations

There are regulatory activities at the Federal and potentially at the state
level which may impact the delivery of 555 calls.  555 assignees should be
aware of these regulations as they impact the service offering 555
assignees may wish to provide.


APPENDIX B

Listing of Grandfathered Numbers

555 Line Number	NPA(s) in Which Line Number is Grandfathered

	1000	207, 401, 413, 508, 603, 617, 802

	1212	All

	1234	505, 602

	1313	506

	1515	201, 207, 401, 413, 508, 603, 609, 617, 802, 908

	1611	207, 401, 413, 508, 603, 617, 802

	1717	207, 401, 413, 508, 603, 617, 802

	1811	207, 401, 413, 508, 603, 617, 802

	4433	808

	4652	203, 212, 315, 516, 518, 607, 716, 718, 914, 917


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