INC NANP EXPANSION WORKSHOP
TITLE: Revisions to D-Digit Report
DATE: January 8, 2001
SOURCE: Penn Pfautz, AT&T
200 S. Laurel Ave
ABSTRACT: This contribution addresses an action item from the INC 53 NANPE workshop to propose revisions to the D-digit Report that, among other things, incorporate the recent contributions. The text also notes open items that need to be resolved.
This contribution has been prepared to assist the INC Workshop. This document is offered as a basis for discussion and is not a binding proposal on AT&T. AT&T reserves the right to add to, amend or withdraw the statements contained herein.
INC Working Document
Draft D Digit Report
REPORT ON NANP
D DIGIT RELEASE
TABLE OF CONTENTS
Appendix A Parking Lot
Appendix B - Contributions
The North American Numbering Plan (NANP)
Expansion Workshop is actively working INC Issue 022, which was accepted
on December 10, 1993. Issue 022 involves the assessment of various
options to expand the NANP from its current ten-digit format of NPA-NXX-XXXX.
An underlying assumption in these options is the release of the D digit.
The D digit is the first digit of a prefix or central office code; it
is the fourth digit in the 10-digit format (NPA-NXX-XXXX). The
present designation of N denotes a number from 2-9. Release of
the D digit would permit any number from 0-9 in that position.
Should the D digit be released it could theoretically increase the quantity
of available NANP numbers by up to 25%. Accordingly, INC issue
159 was opened to investigate the technical impacts of D-digit release
and come up with a recommendation as to whether or not the D-digit should
be released. This report constitutes the resolution to issue 159.
In order to identify the impacts of D-digit release it is necessary to have a clear understanding of the myriad ways in which NANP numbers with o or 1 as the D- digit are used in telecommunication networks. It is useful to distinguish two classes of use, intra- and inter-network. This distinction is important because, if the D-digit is released it will be up to individual carriers to determine how replace D-digit resources in intra- network use but the industry must agree on how to replace D-digit resources in inter-network applications.
Examples of current uses of 0/1XX codes when used as the D digit are as follows:
Editors Note: Its not clear to me whether the two bullets above consistent or redundant. One discusses use of prefixes with 10X codes; the other does not. I believe these codes can be used inter- as well as intranetwork but we should state the case clearly.
Banded WATS Billing Numbers
010-XXXX (WATS Zone 0)
011-XXXX (WATS Zone 1)
012-XXXX (WATS Zone 2)
013-XXXX (WATS Zone 3)
014-XXXX (WATS Zone 4)
015-XXXX (WATS Zone 5)
016-XXXX (WATS Zone 6)
These special billing numbers are recorded
in AMA records and receive special treatment in downstream systems.
In the case of OUTWATS they also control certain aspects of call processing
that determine whether a given call can be placed. These number may
be signaled between switches but are not passed between networks.
Editors Note: Do we have an inconsistency? The first bullet says 01X is used for OUTWATS, the second 1XX. What are the alternatives but assignment of actual billing numbers to these customers?
Pseudo numbers in the format 0XX-XXXX are sometimes assigned to ACD (auto call distribution) groups to conserve "real" numbers. These numbers are always associated with a "real" lead number and are never directly dialed by subscribers.
These numbers are used within a given switch.
Editors Note: What are the alternatives but assignment of actual billing numbers to these customers?
0ZZ codes, used for trunk group selection
in MF signaling, are drawn from spare Toll Center Codes, also GR-690-CORE,
0ZZ and 1NX codes appear in the first stage of MF signaling for FGD inter-exchange calls. Historically, the 0 and 1 were chosen as leading digits to avoid conflict with the 2-9 leading digits of both 7-digit and 10-digit telephone numbers. In areas where D-digit release would be used, a restriction prohibiting the use of 7-digit numbers would be needed for MF FGD signaling. This is likely to be a significant issue only in LATAs that are single-NPA, since trunks would normally be arranged for 10-digit addresses in multi-NPA LATAs.
Editors Note: Should we consider these intra or inter network?
[0/1XX codes are used in the Caribbean for a variety of purposes including, USA direct dialing, international inbound 800, and some OSPS services.] to be clarified
When dialing maintenance numbers to different area codes, the prefixes 012 and 013 can be used .
Editors Note: Can we elaborate on the purpose of these numbers and how they differ from test codes?
(per GR - 145 - CORE, Issue 2 May 1998)
Can we elaborate?
These uses apply across networks.
Today, operators can route to other operators
for operator-to-operator contact for such things as inward BLV (Busy
Line Verification), hard to reach, etc., by dialing NPA-TTC-OSDC,
where NPA is the area code (Number Plan Area), TTC is the Terminating
Toll Center, and OSDC is the Operator Special Dialed Code. OSDCs are
3- to 5-digits in XXX - XXXXX format. The inward calls are routed on
an NPA-TTC basis, if the NPA of the target operator system is different
from the originating system. As with phone numbers, an operator would
not have to dial the NPA if the operator were going inward to an operator
system within their NPA.
Toll Center Codes have the format 0/1XX,
are preceded by the NPA, and are listed in Section 8 of the LERG.
(GR-1144-CORE, OSSGR: Section 6: Signaling, (Issue 1, March, 1997),
Section 9.1 briefly describes the function of these codes, and Tables
13-3 and 13-6 in that document make it clear that routing to an OSS
using Toll Center Codes populates the SS7 Called Party Number parameter
and thus must not conflict with end-user assignable NANP numbers.)
A quick review of the Local Exchange Routing Guide (LERG, table 6ATC)
shows that there are 415 active NPA-ATC combinations in service.
Of those codes, there are 93 different 0XX and 1XX values in use, ranging
from 000 to 131. 22 of those 0/1XX values are used in only one NPA,
while 32 of those values are used in 5 or more different NPAs. LERG
Table 9ATC shows a total of 4278 defined routing patterns that are used
for routing to those 415 ATCs.
Operator services rely on the existing
D digit restriction of a 0 or 1 to identify that the call is from another
operator service. With this restriction lifted allowing NPA-0/1XX-XXXX
calls to be routed from anywhere, there would be no simple method to
determine that the call was from another operator. The switching systems
use the D digit restriction to know that only another operator could
route with a 0/1 in the D digit position. This restriction aids in preventing
toll fraud since the receiving operator position does not bill the call.
A prior condition for D-digit release
would be re-arrangement of the ATC codes to occupy a smaller portion
of the 0XX/1XX spectrum. Since ATC codes are used nationally, not just
regionally, the requirement for an easily recognized and well-segregated
portion of the number spectrum could be met only by re-arranging all
ATCs, not just the ATCs in affected states or areas. Additionally, some
NPAs currently have up to 7 defined ATCs, it would be prudent to allow
a spectrum of more than 10 values, perhaps the range from 000 to 019.
Equipment vendors a variety of
alternatives to accommodate the TTC operator services in an environment
when the D-digit had been released and only certain values were used
for operator calls:
Editors note: Its not clear how
this access control would eliminate the basic conflict: since operators
might have to dial customer numbers with 0/1 D-digits, how would the
OSS distinguish these calls versus inward access?
2.2.2 Special Billing Numbers
Operator Service Systems query the LIDB (Line Information Data Base) to determine whether certain call types may be billed to given numbers. One type of LIDB record is named a Special Billing Number (SBN). SBNs have the format NXX 0/1XX XXXX. SBNs may be used for Calling Cards not associated with line numbers by LECs and non-LECs. When offered by a LEC, the card may be known as an RAO card and with the first three digits identifying the RAO performing the billing. When offered by a non-LEC, e.g., an Interexchange Carrier, the card may be known as a Call Issuer ID (CIID) card, with the first six digits of the card being called the CIID (said sid). SBNs are referenced in several generic requirements documents, including: GR-1158-CORE, OSSGR Section 22.3: Line Information Database, Issue 3, March, 1997 (GR-1149-CORE, OSSGR Section 10: System Interfaces, Issue 2, March, 1997 and GR-1177-CORE, OSSGR: Special Billing Features, Issue 1, June 1997.)
Editors Note: What are the alternatives
to provide equivalent services to customers?
188.8.131.52 Call Issuer I.D. (CIID)
Editors Note: What are the alternatives to provide equivalent services to customers?
It is not necessary to implement D-digit release nationwide and therefore, it could be accommodated on an as needed basis. However, all calling users throughout the NANP would need to have the ability to accommodate the dialing of a 0/1 in the 4th position in order to originate a call to an area that opened up the D-digit. In most cases, if a foreign NPA were dialed, the originating switch would perform a 3-digit analysis on the NPA and route the call to the Inter-exchange network for further routing.In this instance the originating network would only need to translate the first three digits of the foreign NPA and route the call. (The only exception to this is if a foreign NPA is near or adjacent to the dialed NPA then the local switch may perform a 6-digit analysis). With the implementation of number portability, the Inter-exchange carrier would therefore, need to perform some type of analysis in order to properly route the call near the terminating network.The Inter-exchange carrier would therefore need to open up the 0/1XX CO codes in their database as assigned codes.
D-digit release, in certain states or
areas, would mean that subscribers in those states/areas would have
to dial a full national number to complete any call. This dialing might
be in form 1+ 10-Digits or 10-Digits with no prefix. Local 7-digit
dialing could be maintained in states/areas that did not open up the
D-Digit within their own NPA(s).
When, in the future, the NANP is expanded (for example, by expansion to 4-digit NPAs), the consideration above would not be in any way reduced. The use of 0 or 1 as the first digit of the central office code would continue to be subject to same problems and costs described in the previous paragraphs. Therefore, economic studies of cost-versus-benefit for D-digit release should not be limited to the current 10-digit NANP, but should also be applied to future plans.
Editors Note: Do we want to go here?
Given that weve narrowed our NANPE choices down to one
that releases the D-digit, does this make sense? Instead, consider the
The INC NANP Expansion workshop has tentatively concluded that the most viable option for expansion requires that the D-digit not be released until after expansion since D-digit values of 0/1 will be used during permissive dialing to allow expanded format numbers to be distinguished from old format numbers. If the D-digit is released prior to expansion, a different expansion option, which the INC believes will be more disruptive of customer dialing habits and harder for customers to adjust to, would have to be chosen instead. Currently, approximately 10% of NANP resources are set aside for the possibility of that this other, less desirable option must be employed.
Consultations need to occur with the Regulatory Agencies of all nations within the NANP to determine if there is a particular use of the 0/1XX CO codes used in their countries. Preliminary investigation in the Local Exchange Routing Guide (LERG) only revealed codes that have been posted. However, it is assumed that other networks utilize these codes for internal network routing and potentially other purposes.
There may be an issue with certain types
of CPE. This equipment may have been set up with some logic that would
identify the call as invalid if the D-digit is dialed with either a
0 or a 1. The magnitude of this issue can not be determined but with
the other significant numbering changes, e.g., INPA, a percentage of
the CPE equipment could not accommodate the opening up of the B-digit.
Therefore, it could be assumed that a certain percentage of the CPE
equipment may not be able to accommodate the opening up of the D-digit.
There are no known international concerns
with respect to the D digit release since foreign carriers do not typically
analyze calls down to the central office code level. There are
also no restrictions on the values of the digits within the 15-digit
Local switch NPA+0/1 dialing restriction
Many requirement documents include a
reference to the format of 10-digit NANP numbers that are assignable
to end users as NPA NXX-XXXX (with the NPA also having an NXX format).
Particular examples are:
In assessing whether the D-digit should be released, it is necessary to consider
Appendix A Parking Lot
Appendix B Contributions
This contribution, provided by Nortel
Networks, lists existing published uses of a 0 of 1 as the first
NANP NETWORK (AT&T / BOC-LEC / Stentor-Canada / C&W-Caribbean / etc.)
ROUTING CODES 0XX / 1XX / special NXX
Includes historical use of some codes as well as many current generic uses
000 - Rate Quote System
001 -> 005 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
006 - Intl. ATME (TAS-2 Domain ONLY) 006 ->
008 - InWATS OSO routings (from multiple states/NPA's) (1960's/70's)
009 - Rate Quote System
010 - (RESERVED)
011 - IDDD Access / IOTC: International Originating Toll Center
012 - Alt.Route via Principal Tandem (i.e., due to Sector Tandem failure)
013 - (TWX function - but what?)
014 - 4-Row TWX Assistance Opr (954-1212 converts to 014-1212): from 510 TWX (1960's/70's), and Canadian TWX Operator from certain provinces (1960's/70's/80's) sometimes from 710/810/910 TWX (1960's/70's),
015 -> 019 - TWX: NPA/510/610 to N10 routings, N10 to 510/610 routings (note that the N10 SAC is converted to 01N)(1960's/70's and Canada 1980's)
020 -> 021 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
022 -> 029 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
030 -> 031 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
032 -> 039 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
040 -> 041 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
042 -> 049 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
050 -> 051 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
052 -> 059 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
060 -> 061 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
062 -> 069 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
070 -> 071 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
072 -> 079 - (RESERVED- for Autovon?)
080 -> 081 - TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
082->087,9 - InWATS Tndm routings (third-digit Band; 089 Bnd-1)(1960's/70's)
088 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
090 -> 091 -TWX: N10 (4-R) to NPA (3-R) routings (note 0+NPA) (1960's/70's)
092 -> 099 - (spare- available for: TTC's, pseudo c.o. codes, etc.)
100 - Plant Test: Test Board
101 - Plant Test: Test Board
102 - Plant Test: Milliwatt Tone (~1004 Hz)
103 - Plant Test: Signaling Test Termination
104 - Plant Test: 2-Way Transmission and Noise Test
105 - Plant Test:Auto.Transm.Measurement System/Remote Offc.Test Line
106 - Plant Test: CCSA Loop Transmission Test
107 - Plant Test: Par-Meter Generator
108 - Plant Test: CCSA Loop Echo Support Maintenance
109 - Plant Test: Echo Canceler Test Line
110 -> 119 - Operator Codes
11362 - Air-to-Ground / Maritime-Marine / High-Seas / Trains
115X(1) - Leave Word
116X(1) - Calling-Card Validation System
120 - Network Emergency Center
121 - Inward Operator
122->127,9 - InWATS TSO routings (third-digit Band; 129 Band-1)(1960's/70's)
122 - AT&T Ready-Line 800 (1980's)
128 - (RESERVED)
130 - TWX Assistance Operator (3-Row) (1960's/70's)
131 - Directory Operator
132->137,9 - InWATS TSO routings (third-digit Band; 139 Band-1)(1960's/70's)
138 - Mexico: Hermosillo SON- Numbers routings (pre-1977); IDDD Equal Access routings- 011+ (mid-1980's on)
140 - TWX Assistance Operator (4-Row) (1960's/70's and Canada 1980's)
114 - Rate & Route Operator
142->147,9 - InWATS TSO routings (third-digit Band; 149 Band-1)(1960's/70's)
148 - Mexico: Hermosillo SON- Operators (1970's, 1980's)
150 - Cable Control: Hawaii (WAS 157 until 1977, when PR got 800-468)
151 - International Assistance Operator
152->157,9 - InWATS TSO routings (third-digit Band; 159 Band-1)(1960's/70's)
158 - Mexico: Chihuahua CHI- Numbers routings (pre-1977); IDDD Equal Access routings- 01+ (mid-1980's on)
160 - International Operator Center (IOC)
161 - Trunk Trouble Reporting
162->167,9 - InWATS TSO routings (third-digit Band; 169 Band-1)(1960's/70's)
168 - Mexico: Chihuahua CHI- Operators (1970's, 1980's)
170 - Mexico: Monterrey NL- Numbers routings (pre-1977)
171 - Mexico: Monterrey NL- Operators (1970's, 1980's)
172 - Caribbean: Dom.Rep., Puerto Rico, US Virgin Islands (1970's)
173 - Caribbean: Bahamas (1970's)
174 - Cable Control: Puerto Rico, US Virgin Islands (1970's)
175 - Caribbean: Jamaica (Cayman Islands) (1970's)
176 - Caribbean: Bermuda (1970's); Mexico: Mexicali BCN- Operators (1980's)
177 - Cable Control: Dominican Republic (1970's)
178 - Caribbean: Barbados (Dominica, St.Lucia, St.Vincent) (1970's)
179 - Caribbean: Trinidad/Tobago (Grenada thru 1986) (1970's)
180 - Mexico: Mexico City DF- Numbers routings (pre-1977); Numbers routings for _ALL_ of +52 Mexico (1977-on)
181 - Toll Station Operator (for Ring-Downs)
182 -> 188 - ISCs- International Switching Centers (Gateways):
182 - WHPLNY: 02 0201T 4A (70s); 104T 05 0504T 4E (80s); 103T 03 0203T (90s)
183 - NYCMNY: 04 AA02T 4M (70s); 063T 24 BW24T 4E (80s); 111T 55 BW55T (90s)
184 - PITBPA: 02 DG42T 4A (70s); 076T 03 DG43T 4E (80s); 115T 09 DG09T (90s)
185 - JCVLFL: 02 CL01T 4A (70s); 041T 03 CL03T 4E (80s); ATLNGA: 007T 04 TL01T (90s); VANCBC: 02 0104T 4A (70s)- CANADA
186 - OKLDCA: 03 0341T 4M (70s); 070T 06 0344T 4E (80s); SCRMCA: 083T 04 0404T (90s)
187 - DNVRCA: 03 MA03T 4A (70s); 027T 05 ZJ05T 4E (80s); SHOKCA: 084T 05 0296T (90s)
188 - NYCMNY: 10 BW01T 4A (70s); 062T 50 5450T 4E (80s);?013T -- 5410T (90s)? MTRLPQ: 01 0201T 4A (70s)- CANADA
189 - Mexico: Mexico City DF- Operators (1970's, 1980's)
190 - Mexico: Operator routings for _ALL_ of +52 Mexico (1980's)
191 - Conference Operator Loop-Around (1970's); AT&T Advanced 800 Intercept Recording Frames (1980's)
192 - Cable Control: Jamaica (Cayman Islands) (1970's)
193 - Cable Control: Trinidad/Tobago (Grenada/Carriacou) (1970's)
194 - Cable Control: ?? Bahamas ?? (1970's); Mexico: Tijuana BCN- Operators (1980's)
195 - Cable Control: Antigua/Barbuda (Anguilla, Br. Virgin Islands, Montserrat, St.Kitts/Nevis) (1970's); AT&T Advanced 800 (1980's)
196 - TTC for Oprs/Tst at Wayne PA RC (1960's) as: 196+1X1/11XX/10X [Wayne was not Principal City for NPA 215 (Philadelphia-2 was), but circa 1972 Wayne got its own 215+0XX+ Oprs/Tst TTC Code]; Cable Control: Barbados (Dominica, St.Lucia, St.Vincent) (1970's); AT&T International 800 (1980's)
197 - Caribbean: Antigua/Barbuda (Anguilla, Br. Virgin Islands, Montserrat, St.Kitts/Nevis) (1970's); AT&T Direct-Services Dialing Concept (1980's)
198 - TTC for Oprs/Tst for Rockdale GA RC (1960's): 198+1X1/11XX/10X [Rockdale was not Principal City for NPA 404 (Atlanta was), but circa 1972 Rockdale got its own 404+0XX+ Oprs/Tst TTC Code]; Cable Control: ?? Bermuda ?? (1970's); AT&T International City Service Center (ICSC) (1980's)
199 -Mexico: Monterrey NL (Oprs? Numbers?) (1960's); Cable Control: Alaska (1970's); AT&T USA Direct (1980's)
11XX(X) - Operator Codes (Leave Word, BLV/Interrupt, Card Validation):
11362 - Mobile / Marine-Maritime / High-Seas / Air-Ground / Trains
1150(1) - Universal or Coin Callback Operator
1151(1) - Conference Operator
1152(1), 1182(1) - Mobile Service / Air-Ground Operator
1153(1), 1183(1) - Marine Service Operator
1154(1), 1188(1) - Toll Terminal Operator
1155(1) - Time and Charges Callback Operator
1156(1) - Hotel / Motel Callback Operator
1157(1) - IOTC Access Trunk
1158(1) - BOC/LEC Inward Completion Assistance
1159(1) - BOC/LEC Inward Busy-Line Verification
1160(1) - Calling Card Validation (Dial-Pulse)
1161(1) - Calling Card Validation (DTMF)
1162(1) - Calling Card Validation (MF)
OLD 3-digit "Step" Service
Codes (generic uses; both customer and operator)
112 DDD Toll/Tandem/CAMA Switch Access
113 Directory Assistance (Information)
114 Repair Service
115 Mobile/Marine/Air-Ground/Conference Operator
116 Local Area Toll Station Operator
117 Test Board
118-N-1 Ringback (Multi 4/8/10/Rural Party Lines)
119-1 Ringback (Two-Party Lines)
Outward Toll Cordboard Operator