Number Portability Impacts on
IP & Telecoms Interworking
James Yu
NeuStar, Inc.
Number Portability

Number portability (NP) allows the telephone
subscribers to keep their phone numbers when they
change the
–
–
–
Service provider [Service Provider Portability]
Location [Location Portability]
Subscribed services [Service Portability]
Service Provider Portability

Supported in many countries

Adopted schemes vary
–
–
–
–
All Call Query
Query on Release
Dropback
Onward Routing
Some involve centralized databases, others do not.
Service Provider Portability Schemes
DB
Centralized
New
SP
1
Number
Porting
Old
SP
Orig.
All Call Query
Old
SP
2 release w/o #
Donor
1
SP
Orig.
Number
Porting
4
1
2
DB
External or
integrated
Old
SP
3
Orig.
Donor
SP
Number
Porting
New
SP
Old
SP
3 release w/t #
Dropback
Number
Porting
Query on Release
New
SP
1
New
SP
3
4
2
Orig.
Centralized
DB
Donor
SP
2
Onward Routing
DB
External or
integrated
Network Routing

North America
–
–
–
–
–
–
Location Routing Number (LRN) in the ISUP Called Party Number
(CdPN) Parameter for routing
Called directory number (DN) carried in Generic Address
Parameter
Translated Called Number Indicator (TCNI) in the ISUP Forward
Call Indicator (FCI) Parameter set to indicate that database dip has
been performed
Europe
Routing prefix added to the called DN in the ISUP CdPN
Parameter
Proposed ISUP enhancements for NP (Q.769.1)


Adding routing prefix to the Called DN and use Nature of Address (NOA) field to
indicate that or two separate parameters (one is new): one carries the routing number and
the other carries the called DN. NOA used if the routing number is carried in the ISUP
CdPN parameter
Number Portability Forward Information (network option) to indicate whether NP query
is done or not and whether the DN is ported nor not
Database Query

North America
–
AIN (ANSI SS7 MTP/SCCP/TACP)
IN (ANSI SS7 MTP/SCCP/TACP)
ANSI IS-41 (ANSI SS7 MTP/SCCP/TACP)
–
GSM (PCS 1900) MAP (ANSI SS7 MTP/SCCP, ITU-TS TCAP)
–
–

Europe
–
INAP CS1 (ITU-TS SS7 MTP/SCCP/TACP)
–
INAP CS2 (ITU-TS SS7 MTP/SCCP/TACP)
IP & Telecoms Interworking
NP Info.
Call orig.
from SCN
New
SW
GWd1
GWo
GWd2
SIPo
/GKo
PictureTel
Internet
SIPd2
/GKd2
SIPd1
/GKd1
Re-Association
GK - Gatekeeper
GW - Gateway
NP - Number Portability
SCN - Switched Circuit Network
SIP - Session Initiation Protocol
SW - Switch
o - Origination
d - Destination
PictureTel
Old
SW
Number
Porting
Issues

Where to query for NP information
At Originating GW/SIP Server/GK
–
Too many national variations to deal with -> need a common approach
At Destination GW/SIP Server/GK
–
Too late, may be the wrong GW/SIP server/GK; not all the GWs/SIP servers/GKs
can reach all the destination E.164 numbers
Another entity within Internet
–
Additional delay
–
Inefficiency if it also handles user data (e.g., voice/data packets)
The entity that retrieves the NP information may need to
wait and collect all the address information before retrieving
the NP information if overlap signaling is encountered.
Issues (Continued)

How to query for NP information
–
–


SS7/TCAP over IP (many national variations)
A new and common scheme

Need to standardize the scheme

Need to retrieve the routing information (e.g., LRN or routing prefix) if an
existing scheme (e.g., DNS) is enhanced
NP information, if retrieved, needs to be carried over
internet in a common format that can be converted to
national ISUP at the destination GW
ISUP/SS7 over IP (e.g., between two GWs)
–
–
–
Encapsulated ISUP in SIP
SIP protocol
H.225.0
Conclusions


Number portability can occur in the SCNs and within
Internet
Many issues are related to number portability and need to
be addressed altogether
–
–
–
Develop efficient schemes
Use standardize ITU-TS and IETF protocols
Address all aspects of number portability (e.g., not just service
provider portability)