So what does local number portability
mean, and how does a local end office
in the U.S.A. handle it?
I don’t like Rogers Telephone and want
to move my service to Meta-Telecom.
• Local Number Portability (LPN) allows the
subscriber to retain their local phone number
even if they switch to another phone service
provider.
• Allowing them to do this without impairment of
quality and / or service.
• The Telecommunications Act of 1996 requires
local exchange carriers (LEC) to provide this type
of capability. The purpose for this is to remove
the inconvenience of getting a new number every
time the subscriber decides to change their local
phone provider.
What happens once I decide to port
my number to Meta-Telecom?
• Meta-Telecom will generate and send to the
losing LEC an LSR, a End User Form and a Number
Portability Form.
• The Losing LEC will respond with a Firm Order
Commitment.
• Both LECS will execute the service order.
• Meta-Telecom will execute a Service Order
Activation with NPAC. “Neustar”
• Both LECS will update 911 centers.
• Port should be completed.
Who owns the Ported Number
• Number blocks are assigned to OCNs.
• When a subscriber ports their phone number
to a new service provider, the number is still
assigned to the original OCN
• No limit on how many times a subscriber can
port their telephone number.
• If a subscriber terminates their service, the
number ‘snaps’ back to the original OCN.
Basic view of sub dialing ported
number
Lets go thru the steps that occur to hopefully make this call complete
In our call flow we have a customer “sub B” who has ported
their number from LEC-A to LEC-B. And now “sub-A” on LEC-A
is trying to call “sub-B”.
LEC A subscriber
Calls 7087222, a dn that
Ported out of LEC A
When the call is placed. LEC-A will have in its dialing plan a
trigger to launch a TCAP query to the SCP when 7087222 is
dialed.
LEC-A sends a TCAP
Query to the SCP
What is TCAP
• Transaction Capabilities Applications Part
• TCAP messages are designed for accessing
databases or other switches to retrieve
information or invoke features.
• TCAP is used to provide information to SSPs.
This information is often used to enable
successful call completion, but TCAP is not
involved in the actual call-setup procedures.
The SCP receives the TCAP from LEC-A with a transaction Id and component
portion. These tell the SCP who launched the query and for what reason.
The SCP sees
the Subsystem
specified and
does a lookup
The SCP will locate this dn in its database and
return to LEC-A the LRN of the recipient
switch LEC-B
TCAP
response to
LEC-A
What is an LRN
• An LRN is an NPA-NXX
• Operating Companies (OCNs) are assigned
number blocks (NPA-NXX) in the LERG
• Each switch (CLLI code) is assigned one or
more NPA-NXXs
• The OCN assigns one NPA-NXX to be the LRN
for each switch
LEC-A receives the response and will look in a LRN routing table
to determine which outgoing trunk group to send the call.
Check routing tables to
determine outgoing tgrp
LEC-A will send an IAM to LEC-B via the STP. This IAM will contain the LRN and
the GAP.
What is a GAP?
• GAP is by definition; Generic Address Parameter.
• When a originating switch launches a TCAP and receives a
response it will modify the IAM message sent out.
• The original called number becomes the GAP parameter in
the IAM.
• The LRN becomes the called number
LEC-B sees the GAP in the IAM and determines that number now terminates
on their switch and the call is routed to subscriber-b
Let’s dissect a portion of a TCAP message
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MTP SND >> LNK : 0 LST : 0 DPC (NCM): 1-139-255 OPC (NCM): 1-139-40 SLS: 3 SIO S
I : 3 H1H0:9=MSG TYPE
MSG :80 03 0b 10 08 89 00 0b 14 29 68 02 11 05 c3 f8 28 8b 01 2f e2 2d c7 04 5c
46 50 3e e8 25 e9 23 cf 01 01 d1 02 64 03 30 1a bf 35 07 81 05 14 29 68 99 99 8
d 01 01 8f 07 03 10 14 29 68 02 11 9f 34 01 25
CALLED PARTY=4192862011
CALLING PARTY =4192869999
TRANSLATION TYPE=11
SUBSYSTEM NUMBER=248=LNP
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MTP RCV << LNK : 0 LST : 0 DPC (NCM): 1-139-40 OPC (NCM): 239-2-0 SLS: 6c SIO SI
: 3 H1H0:9 MSG :00 03 05 07 02 c1 f8 02 c1 f8 1f e4 1d c7 04 5c 46 50 3e e8 15 e9 13 cf 02
68 01 d1 02 65 01 30 09 8f 07 03 10 14 29 30 00 00
LOCATION ROUTING NUMBER=4192030000
c1=11000001
1 =Subsystem indicator
0 =Point Code indicator
0000 =Global Title indicator
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1=Routing indicator (1= route by DPC & Subsystem)
Now we can look at the IAM being
sent out by the originating SSP.
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ISUP SND >> LNK : 0 LST : 0 DPC (NCM): 1-139-30 OPC (NCM): 1-139-40 SLS: 3 SIO SI : 5 ISUP MSG
TYPE:1 CIC:6 MSG : 00 20 11 0a 03 06 0d 03 90 90 a2 07 03 10 14 29 30 00 00 0a 07 03 10 14 29 68
99 99 ea 01 00 c4 03 14 29 68 c0 08 c0 03 10 14 29 68 02 11 00
MSG TYPE:1 =Initial Address Message
Generic Address Parameter=4192862011
Calling party Number=4192869999
Called Party Number=4192030000, this is the LRN
Originating line info=No special treatment
Jurisdictional Information Parameter=419286
Forward Call Indicator Bit M:Transalated Number Indicator=1
The receiving end will see the GAP field populated in the incoming IAM determine it can route the
call and send back an ACM
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ISUP RCV << LNK : 1 LST : 1 DPC (NCM): 1-139-40 OPC (NCM): 1-139-30 SLS: df SIO
SI : 5 ISUP MSG TYPE:6 CIC:6
MSG : 00 24 00
Message Type:6= Address Complete Message
This gives us a basic idea of how an
LNP call is treated
A little bit more than just a connection from
phone A to phone B.