U.S. patent application number 09/770652 was filed with the patent office on 2001-08-23 for method of enhancing call processing in a number portability environment.
Invention is credited to Slutsman, Lev, Tewani, Kamlesh T., Wilson, Lance Wayne.
Application Number | 20010016039 09/770652 |
Document ID | / |
Family ID | 23821620 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016039 |
Kind Code |
A1 |
Slutsman, Lev ; et
al. |
August 23, 2001 |
Method of enhancing call processing in a number portability
environment
Abstract
A method is provided which reduces post-dial delay in a number
portability environment. In particular, a switching office which
controls call routing to portable numbers (NPA-NXXs) contains a
cache for which location routing number response information may be
stored. The processing office concurrently checks the cache for LRN
response information corresponding to the dialed number and
launches a query to a number portability database. Thus, if the LRN
response information in the cache is valid then the call will be
routed in the timeliest manner. However, if either the cache does
not have any LRN response information or the LRN response
information in the cache proves not to be valid then, the switching
office will have received the LRN response information from the
database more quickly based on the concurrent launching of a query.
Therefore, a more timely attempt at establishing a proper
connection to the dialed number will occur thereby reducing
post-dial delay.
Inventors: |
Slutsman, Lev; (Wayside,
NJ) ; Tewani, Kamlesh T.; (Freehold, NJ) ;
Wilson, Lance Wayne; (Marlboro, NJ) |
Correspondence
Address: |
KENYON & KENYON
1500 K STREET, N.W., SUITE 700
WASHINGTON
DC
20005
US
|
Family ID: |
23821620 |
Appl. No.: |
09/770652 |
Filed: |
January 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09770652 |
Jan 29, 2001 |
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09458660 |
Dec 1, 1999 |
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6233331 |
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Current U.S.
Class: |
379/221.13 |
Current CPC
Class: |
H04M 2215/46 20130101;
H04M 15/49 20130101; H04M 15/00 20130101; H04M 15/745 20130101;
H04M 2215/0108 20130101 |
Class at
Publication: |
379/221.13 |
International
Class: |
H04M 007/00 |
Claims
What is claimed is:
1. A method for reducing post dial delay in a network that
providing a number portability environment, the method comprising
the steps of: receiving a dialed number; recognizing said dialed
number as a portable number; checking a cache to determine if a
location routing number for said portable number has been cached;
querying a database that correlates portable numbers to respective
location routing numbers to determine a location routing number for
said portable number; if said step of checking determines a
location routing number to be cached for said portable number then
attempting to route the call to said portable number using location
routing number response information from said cache; receiving
location routing number response information corresponding to said
portable number from said database in response to the step of
querying; and if said step of checking determines no valid location
routing number to be cached for said portable number, then
attempting to route the call to said portable number using said
location routing number response information received from said
database.
2. The method of claim 1 further comprising the step of updating
said cache using the location routing number response information
received from said database.
3. The method of claim 1 wherein said step of querying said
database occurs while said step of checking said cache is
performed.
4. The method of claim 1 wherein said step of querying said
database occurs before said step of attempting to route the call to
said portable number using said location routing number.
5. The method of claim 1 comprising the further step of receiving a
notification of failure to complete the call to said portable
number after attempting to route the call using said location
routing number from said cache.
6. The method of claim 5 comprising the further step of attempting
to route the call to said portable number using said location
routing number response information from said database prior to
receiving said notification if the location routing number response
information from said database differs from the location routing
number response information from said cache.
7. The method of claim 6 further comprising the step of updating
said cache using the location routing number response information
received from said database.
8. In a communication system in which a telephone number is
portable between at least two service providers, a method for
reducing post-dial delay for an originating party calling the
portable number, the method comprising the steps of: receiving a
dialed number at a local office associated with the originating
party; checking a cache associated with said local office for a
location routing number associated with said dialed number;
concurrent with said step of checking, launching a query to a
database for obtaining a location routing number for said dialed
number; receiving said location routing number from said database
in response to said query; and if said step of checking determines
a location routing number to be cached for said portable number,
then, prior to receiving a response from said database, attempting
to route the call to said portable number using said location
routing number from said cache.
9. The method of claim 8 comprising the further step of updating
said cache using said location routing number received from said
database.
10. The method of claim 8 wherein a location routing number from
said cache corresponds to a first service provider and a location
routing number from said database corresponds to a second service
provider.
11. The method of claim 10 wherein the first and second service
providers correspond to first and second local switching offices
respectively.
12. The method of claim 10 wherein the first and second service
providers correspond to first and second carriers respectively.
13. In a communication system in which a telephone number is
portable between at least two service providers, a method for
reducing post-dial delay for an originating party calling the
portable number, the method comprising the steps of: receiving a
dialed number; checking a cache for a location routing number
associated with said dialed number; concurrent with said step of
checking, launching a query to a database for obtaining a location
routing number for said dialed number; receiving said location
routing number from said database in response to said query; and if
said step of checking determines a location routing number to be
cached for said portable number, then, prior to receiving a
response from said database, attempting to route the call to said
portable number using said location routing number from said cache.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for improving call
processing in a number portability environment. Specifically, the
present invention relates to a method for reducing post-dial delay
while routing calls in a number portability context.
[0002] The U.S. telecommunications network is in a state of
transition. In the not too distant future it is expected that the
monopoly held by local exchange carriers will be substantially
altered and that Competitive Access Providers (CAPs) will begin to
provide competitive provide local exchange service. To accomplish
this without creating an excessive burden on customers who wish to
receive service from a CAP, the customers will be able to change to
a CAP without requiring the change of a telephone number. This type
of flexibility is referred to as service provider number
portability. It enables the subscriber to change his or her service
provider while maintaining the same directory number. The public
policy goal is to ensure that there is no performance degradation
between carriers.
[0003] It is also expected that subscribers will be able to move
between geographic locations within some reasonably defined region,
for example, within the same LATA, while retaining the same
telephone number. This is referred to as geographic portability. In
this case the subscriber may or may not change service
providers.
[0004] An additional type of portability relates to a customer's
desire to change the type of service in use. For instance, a
customer may change from Plain Old Telephone Service (POTS) to IDSN
service and wish to maintain the same directory number. This is
referred to as service portability.
[0005] AT&T has already proposed a system for providing both
service provider and geographic number portability. This system
uses a mechanism referred to as the Location Routing Number (LRN)
mechanism. In the Location Routing Number mechanism during call
processing a local switch analyzes the dialed number to determine
both whether that number is from a portable NPA-NXX, that is,
whether at least one NPA-NXX-XXXX has ported to another local
switch, and whether the call is interswitch, that is whether or not
a different local switch serves the destination number. If the
number's NPA-NXX is determined to be portable and if the call is
interswitch then the network switch launches a query to a number
portability (NP) database. If the number has been ported the
database then returns a location routing number (LRN) of the
recipient switch to which the dialed number has been ported. The
querying switch receives the LRN and uses it to route the call to
its correct destination.
[0006] If the number has not been ported then the NP database
returns the dialed number (DN) and the switch appropriately routes
the call.
[0007] Examples of the call flow in the LRN mechanism are
illustrated in prior art FIGS. 1 and 2.
[0008] FIG. 1 illustrates call processing in an LRN mechanism when
a call from a calling party A to a called party B is a local
interswitch call. In the example, in step 1 party A (having number
212-949-3001) dials 212-984-3001, the number assigned to party B.
The end office (EO) 10 of local service provider (LSP) 1 receives
the dialed number and determines that the number's NPA-NXX is
portable. EO 10 then launches a query via Signaling Transfer Point
(STP) 20 to a number portability (NP) database 30. The query
includes the dialed number received by EO 10. The NP database 30
then returns the location routing number to the EO 10. The first
six digits of the LRN are indicative of a particular LSP EO. The
LRN is populated in the Called Party Number ISUP (ISDN user port)
parameter of the Initial Address Message (IAM) of the Signaling
System 7 (SS7) protocol. The dialed number is placed in the generic
address parameter (GAP). Furthermore, an indicator is set to
represent the fact that the routing information is based on a query
to the database. When the EO 10 receives this information it then
routes the call to the tandem switch 40 based on the first six
digits of the LRN. The tandem switch then routes the call to the
end office of the LSP3, 50, to which called party B is presently
ported rather than the end office of LSP 2, 60, to which the called
party B was previously ported. Finally, in a fifth step the EO 50
presently serving the ported subscriber recognizes its own LRN and
obtains the dialed number from the generic address parameter and
uses that information to complete the call to station B. In
summary, for interswitch calls to portable NPA-NXXs the end office
switch 10 launches a query to a database to obtain routing
information for the end office which is servicing the ported
customer.
[0009] FIG. 2 illustrates a similar situation in the context of an
interLATA call where the call must be serviced by an Inter-Exchange
Carrier (IXC). Like elements in FIGS. 1 and 2 bear identical
reference numerals. In this instance the EO 10 determines that the
call is an interLATA call and therefore sends the dialed number
information to the IXC originating switch 15. The IXC recognizes
the dialed number as pertaining to a portable NPA-NXX and generates
a query using the dialed number (212-984-3001 in the illustrated
example). The query goes to the Signaling Transfer Point (STP) 25
and is forwarded to a number portability (NP) database 35. The NP
database 35 could be a national universal database. The
distinctions between the database 35 of FIG. 2 and the database 30
of FIG. 1 could correspond to the differences between the national
and local databases described in co-pending application Ser. No.
______, the entire disclosure of which is incorporated by reference
hereto. As in the case of the query response in FIG. 1, if the
number has been ported, the NP database 35 provides the LRN
information associated with the dialed number. The originating IXC
switch formats an ISUP IAM and places the LRN information (here
212-484-9999) in the called party number parameter. The dialed
number is stored in the generic address parameter and the M-bit of
the Forward Call indicator (FCI) is set to indicate that the NP
database 35 was queried. The originating IXC 15 then routes the
call to terminating IXC switch 45 based on the first six digits of
the LRN. The terminating IXC switch determines a routing path to
the EO 55 of LSP 3, 50, based on the first six digits of the LRN.
The end office 55 recognizes its own LRN and then obtains the
dialed number from the GAP and completes the call to station B.
[0010] In the two examples described, a query is launched to the
database, either local database 30 or national database 35 each
time an interswitch call to a portable NPA-NXX is detected. As a
result, the system generates a large number of queries. In fact,
for a frequently dialed number a query related to that dialed
number may have been processed only a few minutes or even perhaps
just a few seconds, earlier. These queries come at a cost. First,
there is the load on the system in query traffic. Then there is the
processing to be done at the NP database to respond to all queries.
Finally, there is a built-in delay for processing all interswitch
calls to portable NPA-NXXs since a query must be launched and
processed before the call is routed. In a co-pending application by
the same inventors filed on the same date as the present
application it is proposed to employ a cache at the switching
office that launches the database query. The cache is checked
before a query is launched so that if LRN response information is
in the cache there is no query unless upon attempting a connection
using the LRN response information in the cache the attempt fails
because the cached information is incorrect. That deployment of a
cache reduces queries. However, the inventors have also noted that
post-dial delay, a phenomenon of concern to service providers, can
be exacerbated by delaying the launch of database queries until an
attempt to connect using cached LRN response information fails. The
communication industry has recognized that the delay experienced by
a calling party after completing the dialing of a number can have a
significant impact on the perception of the service provided. Too
long a delay may present a very clear indication that the called
party is now ported to a different service provider and may suggest
that there is a degradation of service as a result of the porting.
There is no agreement within the industry regarding acceptable
values for post-dial delay. It would therefore be beneficial to
reduce post-dial delay wherever possible to avoid the appearance of
service degradation to the calling party.
SUMMARY OF THE INVENTION
[0011] The present invention is directed to a method for enhancing
call processing in a number portability environment. In particular,
the invention reduces post-dial delay enabling faster attempts at
routing calls to portable numbers.
[0012] In accordance with the present invention a cache memory is
associated with the local exchange or inter-exchange carrier switch
responsible for processing the call to the portable NPA-NXX. The
cache memory stores, for a limited period of time, LRN response
information received from the number portability database in
response to queries launched regarding dialed numbers associated
with portable NPA-NXXs. At the same time the switch checks the
cache upon receipt of a dialed number associated with a portable
NPA-NXX to determine if the cache contains LRN response information
for that number, it launches a query to a number portability
database. If the cache contains such response information, then the
local exchange or IXC attempts to route the call based on the
cached LRN response information. If the cache does not contain
information relating to the dialed number, or if the attempt to
route the call based on LRN response information in the cache is
unsuccessful, then LRN response information received from the
earlier query is used for routing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1 and 2 illustrate call flows for known number
portability systems.
[0014] FIGS. 3 to 5 illustrate call flows in accordance with an
embodiment of the present invention.
[0015] FIG. 6 illustrates the format of parameter information
useable in connection with an embodiment of parameter information
useable in connection with an embodiment of the present
invention.
[0016] FIG. 7 illustrates call flow in a modification of an
embodiment of the present invention.
DETAILED DESCRIPTION
Overview
[0017] In accordance with an embodiment of the present invention, a
cache is associated with the switching office which is responsible
for launching queries to a number portability database. Every time
the switching office receives a portable number it launches a query
to the number portability database and checks the cache to
determine whether location routing number response information for
a received dialed number is available in the cache. This checking
operation is performed concurrently with the launching of a query
to the number portability database. If LRN response information is
found in the cache, the switch will attempt to complete the call.
This will increase the speed with which calls are processed since
it is quicker to access LRN response information from a cache
associated with the switch than it is to wait to receive data back
from the number portability database after launching a query. If,
however, the attempt to connect the call fails, the switch should
have already received or is about to receive the LRN response
information from the NP database. Thus, another attempt to connect
the call will be made with a substantially shorter delay than if
the switch waited until notice of failure to connect before
launching the query. The result is a reduction of post dial delay.
This reduction enhances the calling party's perception of the call
processing operation. Before describing the call flows for
implementation of the present invention it is helpful to understand
the terminology typically used in the field of number portability.
The following glossary is useful in that regard.
[0018] Local Service Provider (LSP): A local service provider
refers to the provider of local access functionality to an end
customer. LSPs are synonymous with local exchange carriers (LECs),
alternate local exchange carriers, competitive access providers,
and other terms that may be used to refer to providers of local
access.
[0019] Numbering Plan Area (NPA): The initial group of three digits
of a North American numbering plan (NANP) number. The format of NPA
is NXX where N is any digit from 2 to 9 and X is any digit from 0
to 9.
[0020] Number Portability: Gives the subscriber the ability to move
from one end office (i.e., switch) to another and keep its original
directory number (DN). There are three types of number portability
as described in the background section of the application. FCC and
state regulatory activities primarily deal with the implementation
of service provider number portability.
[0021] Default LSP: In today's environment, the local exchange
routing guide (LERG) identifies which NPA-NXXs are assigned to
which LSP end offices. The LSP appearing in the LERG is the default
LSP for an NPA-NXX and the default LSP for the line numbers is that
NPA-NXX.
[0022] Default Routing: Refers to routing a call to the default LSP
based on the first 6 digits (NPA-NXX) of a NANP number.
[0023] Ported Number: A ported number is an end customer's number
which is no longer served by the default local service provider as
defined in the local exchange routing guide.
[0024] Location Routing Number: A location routing number is an
identifier of an LSP end office. The LRN of an LSP end office is
defined as a 10 digit number of the format NPA-NXX-XXXX such that
the first 6 digits is an NPA-NXX assigned (in the local exchange
routing guide) to the LSP end office. Also, a 6 digit translation
on the NPA-NXX of the LRN will result in routing calls to the LSP
end office.
[0025] Number Portability (NP) Database: An NP database is a
database which stores number portability data, such as the LRNs for
ported numbers. Switches will query a number portability database
with a dialed number to obtain number portability information for
the dialed number.
[0026] Destination Number: For routing a call the number used to
query the number portability database will be referred to as the
destination number. The destination number can be the number
received from the incoming called party number (CdPN) parameter
(e.g., dialed number) or the number derived after service
processing (e.g., the translated number after 800 service
processing has been applied).
[0027] Calling Party Number (CPN) Parameter: An existing SS7 ISUP
(ISDN user part) initial address message (IAM) parameter which
currently carries the calling party number.
[0028] Called Party Number (CdPN) Parameter: An existing SS7 ISUP
initial address message parameter which currently carries the
destination number. Switches use the number populated in this
parameter to determine how to route the call.
[0029] Generic Address Parameter (GAP): The GAP is an existing
optional SS7 ISUP initial address message parameter. Multiple GAPs
can be defined for a call. Within the LRN approach, the dialed
number is populated in the GAP when the LRN is populated in the
Called Party Number parameter instead of the called party
number.
[0030] Bits M and N of a forward call indicator: Bits M and N have
been defined as associated with number portability in the current
invention.
[0031] Portable NPA-NXX: An NPA-NXX is defined as portable if it
has one or more ported numbers. That is, destination numbers with a
portable NPA-NXX are no longer associated with a unique LSP.
[0032] Number Portability (NP) Capable/Non NP Capable Switch: An NP
capable switch is a switch which has the capability to support the
LRN solution for number portability. A non-NP capable switch is a
switch which does not have the capability to support the LRN
solution for number portability. A non-NP capable switch can have
numbers ported to and from it and have an LRN assigned to it.
However, it does not have the capability to query a number
portability database nor to recognize its own LRN and retrieve a
ported destination number from the generic address parameter.
Description of the Proposed Call Flows
[0033] For purposes of the following discussion the assumption will
be that at some time prior to the call being processed a called
party B was served by end office 160 of local service provider 2
and has been ported by the end office 150 of local service provider
3. The shift between service providers could constitute either
geographic restricted portability of the calling party B, or
service provider portability, that is a change to a different local
service provider, or both. In either portability circumstance the
ported party B is served by a different end office and hence a
different "service provider".
[0034] FIG. 3 illustrates the circumstance where the calling party
A, being serviced by its local service provider can call the
(ported) called party B with LRN response information being
available to the end office of the LSP 1. More specifically,
calling party A dials the ported number, here 212-984-3001. The end
office 110 receives the number and detects that 212-984 is a
portable NPA-NXX and that the call is interswitch, i.e., end office
110 does not "serve" called party B. The end office then does two
things. It launches a query to number portability database 140 via
Signaling Transfer Point (STP) 130. The end office also checks
cache 100 to determine whether it contains location routing number
response information corresponding to the dialed number. In this
call processing sequence, the cache does include the LRN response
information including the LRN of 212-484-9999. Thus, the end office
110 places the LRN in the called party IAM parameter and places the
dialed number in the generic address parameter. A query bit
indicator, bit N of the FCI is also set in the IAM message to
indicate that the LRN response information has not come from the
number portability database. The end office then routes the call
via tandem switch 120 to the end office 150 of LSP 3 identified by
the LRN from the cache. The LSP 3 end office then recognizes its
own LRN in the CdPN parameter, obtains the dialed number from the
generic address parameter, and completes the call to station B. In
this configuration then, in comparison to the known LRN mechanism
described above, a cache memory is provided in association with the
end office 100 and is checked to determine if call routing can be
done before receiving the LRN response information from the NP
database.
[0035] The call flow illustrated in FIG. 4 relates to that
circumstance where the cache memory does not contain LRN response
information for the dialed number. Here again the calling party
dials 212-984-3001. End office 110 detects that the NPA-NXX is
portable, launches a query to NP database 140, and checks cache 100
to determine if the cache contains any LRN response information
relating to the dialed number. In this instance the end office does
not detect any valid information in the cache relating to the
dialed number. The term "valid information" is used to indicate
that information within the cache may be deemed to be unreliable
after some specified period of time. Therefore, even if response
information exists in the cache for a particular called number,
those entries may have been in the cache for such a period of time
that statistically they are no longer reliable and are therefore
treated as invalid pieces of information. More information
regarding the consideration given to LRN information within the
cache will be provided below. Continuing with the call flow of FIG.
4, since the cache does not contain any information regarding the
dialed number, end office 110 awaits a response to the launched
query. The NP database returns LRN response information
212-484-9999. As with the call flow of FIG. 3, the called party
number parameter is populated with the LRN while the generic
address parameter is populated with the dialed number. In this
instance however, the query indicator is adjusted to reflect the
fact that the LRN response information comes from the number
portability database. The LRN response information is then used by
end office 110 to route the call to the end office to which station
B is ported as indicated by the LRN, that is LSP 3 end office 150.
That LSP then recognizes its own LRN and obtains the dialed number
information from the generic address parameter and completes the
call to station B.
[0036] In addition to routing the call using the LRN information
from the database, the LRN response information is also provided to
the cache 100 in association with the dialed number. The cache
entry is designated as a valid entry and is considered as such for
some set period of time. For instance, when the results of a query
to the number portability database are stored in the local cache, a
timer could be set that defines the maximum time interval for which
that cached information may be considered as current or valid. At
the expiration of this timer the entry from the local cache should
be flushed. In the event that the cache is full at the time LRN
response information is provided for a query and a new entry needs
to be stored, the oldest cache entry (that is, the entry whose
local cache timer is closest to expiration) must be flushed. It
would be beneficial if the timer is refreshed/reset to the maximum
timer value every time there is a successful hit in the local cache
for this dialed number. This will tend to ensure that the
information for the numbers that are dialed frequently will be
readily available in the local cache thereby reducing post dial
delay for calls to such numbers.
[0037] The situation may arise where the LRN response information
in the cache may be still considered timely within the criteria
described above but in fact, inaccurately reflects the end office
which serves the called party B. FIG. 5 of the present application
provides a call flow diagram for number portability processing in
that instance. In this instance it will be assumed that the cache
100 stores LRN response information indicating that a called party
B is ported to LSP 2 of end office 170 and that LRN response
information is still considered timely in the cache. Nonetheless,
calling party B has been ported to end office 150 for LSP 3. In
this circumstance then the end office 110, upon detecting the
NPA-NXX to be portable and the call to be interswitch, examines the
cache and determines that LRN response information is present in
the cache. In this instance the LRN response information is the LRN
for end office 170, 212-984-9999. This information is placed in the
called party number field and the dialed number is placed in the
generic address number parameter field. The end office 110 then
attempts to route the call to the end office corresponding to or
identified by the called party number, in this instance end office
170 corresponding to LSP 2. The called party B is no longer served
by end office 170. The call to that end office is cleared and a
code is sent back to indicate that the end office 170 is not ported
to the dialed number. Since the end office 110 launched a query to
the number portability database at the same time it checked the
cache, it will have either received or is about to receive the LRN
response information from the NP database at the time the code is
received. The more authoritative LRN response information from the
NP database, in this example 212-490-9999, is then populated in the
called party number parameter and the generic address parameter
continues to reflect the dialed number, 212-984-3001. In this
instance the number portability query indicator is changed to
reflect that the number portability database has been queried and
that the LRN response information comes from a more authoritative
source than the local cache.
[0038] FIG. 6 illustrates the format of the FCI parameter of the
IAM. Of particular significance in this format are bits M and N.
Bit M is used by the conventional LRN approach to indicate whether
an NP database query has been performed. Of more significance to
the current invention is the status of bit N which indicates the
relative authority to be ascribed to the CdPN namely that the
information in the IAM has been obtained from the local cache
rather than from the number portability database.
[0039] The call flows described in connection with FIGS. 3 to 5 all
relate to providing a cache in the end office of the local service
provider 1 associated with the calling party A and launching a
query to the database concurrently with checking the cache. Thus,
there are improvements over the system illustrated in FIG. 1. It is
also presumed that one of ordinary skill in the art would be able
to recognize employing the cache memory at the switching office of
the inter-exchange carrier which is determined to be responsible
for call processing as in the example of FIG. 2. Here the cache
would then be associated with the IXC originating switch, for
example, 15 in FIG. 2. The decision making tree however, would be
very similar to the present invention and would provide that for
every interswitch call to a portable NPA-NXX, a query is launched
to a NP database while the switch checks a local cache for any
location routing number response information. Then if either the
cache does not contain LRN response information or, in a worst case
scenario, if an IAM clearing message indicates that the LRN
response information retrieved from the cache is incorrect the
number portability database response information is available from
the parallel.
[0040] One skilled in the art would recognize that the present
invention would still be effective even if the switch did not
launch a query for each and every portable NPA-NXX. It is possible
that a class of portable NPA-NXXs may not experience unacceptable
post dial delay even if a query is only launched after checking the
cache or receiving a notice of failure to connect. In that instance
the switch might concurrently check the cache and launch queries
only for those portable numbers not in that class.
[0041] FIG. 7 illustrates a modification of the present invention
illustrated in FIGS. 3 to 5 wherein the calling party is associated
with a local service provider 1 which hands off the call to a
homogeneous sub-network of LRN capable switches via MF signaling.
In that instance, it is the LSP2 end office which would contain the
cache. Then that end office would launch a query to the number
portability database and would check that cache for LRN response
information. Subsequent call processing would be the same as
described above.
[0042] The present invention can be implemented on a switch such as
a 4ESS or 5ESS from Lucent Technologies with modifications to call
processing software that reflect the call flows described
herein.
[0043] The present invention provides a unique call processing
scheme which reduces the post dial delay that might otherwise arise
in processing calls to portable numbers. Thus calls to portable
numbers, regardless of whether the change in service provider
relates to limited geographic portability or simply selecting a
different access provider, can be processed more quickly.
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