Local Number Portability (LNP) allows a customer the ability to transfer either an existing fixed line or mobile telephone number assigned by a local carrier and reassign it to another carrier. The IMG now supports taking the LNP data in the R-URI on the SIP leg and interworking it into the R-URI and ISUP MIME on the SIP-I leg. The IMG also supports taking the R-URI message from the SIP-I leg and interworking it into the R-URI message on the SIP leg. Feature F-5282 is by default always enabled and does not need any special configuration for it to function.  

The LNP data in the IAM message is encapsulated in the GAP and FCI parameters. The GAP digits field carries the ported number (equivalent to RN tag). The FCI M-bit carries the ported number indication (equivalent to NPDI tags). For SIP-I, the LNP data in the R-URI and in the IAM are redundant. The IMG will retrieve the LNP data from the R-URI and the IAM message will not be parsed.

SIP-I to SIP scenario:

SIP-I leg- The R-URI will be parsed to retrieve the LNP data (RN and NPDI tags).

SIP-I leg- The IAM in the ISUP MIME will not be parsed.

SIP leg- The LNP data will be relayed in the R-URI as RN and NPDI tags.

SIP to SIP-I scenario:

SIP leg - The R-URI will be parsed to retrieve the LNP data (RN and NPDI tags).

SIP-I leg - The LNP data will be relayed in the outgoing SIP R-URI as RN and NPDI tags in the user-info part.

SIP-I leg - The LNP data will also be relayed in the outgoing IAM (ISUP MIME) as GAP and FCI parameters.

The LNP data is relayed between SIP and SIP-I and no processing of the data will take place.

Call Flow Diagram:

The Call Flow below represents the interworking of LNP from both SIP to SIP-I and SIP-I to SIP. The call flow details a Video to  Call is received from MSC A in SIP-I format. The IMG will receive the call and will add the LRN and NPDI parameters into the INVITE message sent out on the SIP leg to the Video Gateway. The Call Flow below references the Call Trace that is linked in the 'Call Trace Example' in next section.

Open

Call Trace Example:

 Call Trace - LNP (SIP-SIPI)

Configuration:

There is no configuration required for Feature F-5282 LNP Handling for SIP-I. The feature by default is always enabled.

Additional Information:

• In the R-URI, the RN and the NPDI tags can be located in the “userinfo” part or in the “uri-parameters” part.

• The IMG will decode the tags at the two locations.

• The IMG will encode the tags only at the “userinfo” location.

  • When viewing a Call Trace and the Routing Number (rn) and Number Portability DIP indicator (npdi) are included in the INVITE messaging, the format can change dependent on the interworking scenario. Below is a table displaying the format for each scenario