LNP / Porting FAQ

This is a follow up to my other post on LNP (Anatomy of Local Number Porting in Australia) with some of the frequently asked questions.

For more info on the routing I’ve also written about Call Routing in LNP.

I’ve cited the relevant section of the code below and you can find the code itself here – Communications Alliance – Local Number Portability.

Why am I still billed after a number is ported out?

The Losing CSP does not need to take any action to disconnect Customer’s Telephone Number(s).


This means just porting out a number from a CSP doesn’t mean billing from the Loosing CSP will stop.

Continuing contractual agreements between the customer and Loosing CSP may still be in place and the customer is responsible for requesting the services be cancelled with the Loosing CSP.

Some CSPs work out that if you’re porting out a number you don’t want their services anymore, but they’re not obliged to and most will do what they can get away with.

What is a Bilateral Peering Agreement?

While a customer is legally entitled to move a number they have full control over (As outlined in Telecommunications Numbering Plan 2015), in practice phone numbers can only be moved from one carrier to another if both CSPs have a Bilateral Peering Agreement with each other.

These agreements primarily sort out the commercials of how much they’ll pay each other per port in / out.

It’s worth also noting that the Code only defines the minimum standard and process, two CSPs that have a bilateral peering agreement in place are able to process ports faster and more efficiently than the minimum standard outlined in the code.

Carriage Service Provider vs Carrier?

I’ve been sing the term Carriage Service Provider and Carrier interchangeably.

The difference as far as the code is concerned is one is who a customer pays for the service, while the other is the provider of the service. Generally it’s safe to assume that the CSP is also the Carrier and not a re-seller.

Donor Carriers

Under the Numbering Plan managed by ACMA numbers are allocated to certain CSPs.

These numbers can be ported to other CSPs (this is after all what LNP is all about) but after the number is routed to a different carrier the Donor Carrier remains the carrier listed in the Numbering Plan.

The Donor Carrier is responsible for Donor Transit Routing (A temporary redirect to numbers that have been ported away recently) for any numbers that have recently been ported out, and publishing the number and new carrier details for each number ported out in their PLNR file.

Donor Transit Routing

Under the Numbering Plan managed by ACMA numbers are allocated to certain CSPs.

These numbers can be ported to other CSPs (this is after all what LNP is all about) but after the number is routed to a different carrier the Donor Carrier remains the carrier listed in the Numbering Plan.

In a scenario where a call needs to route to a destination where the current carrier for that destination is unknown, the call is routed to the Donor Carrier, as that’s who the number is originally allocated to by ACMA.

Upon reciept of a call by the donor carrier to a number that has been ported out, the donor’s switch finds the correct Access Service Deliver (ASD) and redirects the call to them.

This is a temporary service – CSPs are only obliged to do this for 5 days, after which it’s assumed the PLNR file of the donor will have been read by all the other CSPs and they’ll be routing the traffic to the correct CSP and not the Donor CSP.

Third Party Ports

Third Party Porting is where the Donor Carrier is neither the Losing Carrier or the Gaining Carrier. Third Party Porting requires bilateral agreements to be in place between each of the parties involved.

As we just covered ACMA allocates numbers to CSPs, when a number is ported to a different CSP the number is still allocated to the original CSP as far as ACMA and The Numbering System are concerned.

The CSP the number was originally allocated to is the Donor CSP – forever.

Let’s look at a two party port first:

  • A number is allocated by ACMA to CSP 1
  • The customer using that number decides to port the to CSP 2 using the standard LNP process
  • CSP 1 performs Donor Transit Routing for the required 5 days and updates it’s PLNR file to denote that the number has been ported to CSP 2

Now let’s consider a three party port, carrying on from the steps above.

  • The Customer decides they want to move from CSP 2 to another CSP – CSP 3
  • At the time of the port the donor CSP (CSP 1) must:
  • CSP 1 must update it’s PLNR records for this number to denote it’s no longer with CSP 2 but is now with CSP 3
  • CSP 1 must provide Donor Transit Routing for the required 5 business days – redirecting calls to CSP 3

So even though the number is moving from CSP 2 to CSP 3 as the number was originally allocated to CSP 1, it is, and will always be the Donor Carrier and as such has to provide Donor Transit Routing and update it’s PLNR each time the number is ported.

Port Reversal / Emergency Return

Ports have an emergency return window inside which the port can be reverted. For Cat C ports this invovles the project manager of one CSP contacting the project manager for the other CSP and requesting the return.

In the event the end customer has requested the Port Reversal / Emergency return they’re typically liable for a very hefty fee to do so.

Give Back & Quarantine of Numbers

After a number is no longer required, it’s given back to the donor carrier who places it in quarantine and typically does not reallocate the number for 6 months.

In some cases such as a wronly cancelled number the customer may be able to get a number that’s been cancelled back while it’s in it’s quarantine state, however this is not required and up to the donor carrier.

Including Customer Account Numbers when Porting

Prior to 2016, a customer moving from one CSP to another CSP were required to include their account number (“Service Account Number”) they had with the Loosing CSP to the Gaining CSP when submitting the Port which was verified against the Loosing Carrier’s records to ensure the correct Customer / Service combo.

This led to a lot of ports being rejected unnecessarily due to mismatched account numbers, as such the the requirement to include a valid matching account number with the loosing CSP has been removed.

Service Account is to remain as a mandatory field, and a standard validation but any mismatches are not to be rejected.

Where’s Cat B & Cat D?

Cat B Dropped in 2013 revision due to lack of use.

Cat D is almost the same as a Cat A port but allows services with an active ULL diversion to be ported. These are quite rare and a very specific use case.

Why is my Cat C Port taking so long?

You may find after submitting a port the date you’ve got back for porting is months away. The Loosing Carrier sets the porting date, and as they’re loosing the customer, they’re often not so keen to action the port quickly when they’re loosing the customer after all.

Lead Times are determined by the Losing Carrier. These may vary by product including variations due to the size of the product or the number of sites to which a particular service is offered.


Tidbit: One of Australia’s largest carriers has a 20,000 number per day limit on porting, meaning they’re only able to process up to 20,000 ports per day in or out. Once that limit is reached no more ports can be accepted for that day, so the ports are delayed until the next day, etc, etc, leading to considerable lead times.

The code requires CSPs to keep Service Metrics on porting time-frames, but there’s no penalty for being slow. (Section 3.6)

Third Party ports also take a lot longer due to the requirement to find a time window that suits all 3 carriers.

Can I arrange my numbers to be Ported after-hours?

CSPs are not required to port numbers outside of the “Standard Hours” defined in the code. (Section 3.8.1 )

However, most CSPs have included support for this inside their bilateral agreements with other carriers. This typically costs more for the customer, but also comes with the added risk of if the port fails there are fewer technical / engineering resources available at the Loosing and Gaining Carrier’s respective ends to sort it out if something goes wrong.

What’s a PNO?

Porting Notification Order – A message containing either a Simple Notification Advise (SNO) for Simple (Cat A) ports, or a Complex Notification Advise (CNA) for Complex (Cat C) ports.

Each PNO contains a unique sequential reference number to differentiate / associate the PNO with a particular porting request.

PLNR – Ported Local Number Registry

PLNR is nothing more than a giant text file, containing a list of numbers originally allocated to that CSP but that have been ported to another CSP, and with each number that’s been ported out the carrier code of the CSP it’s now with.

Information to facilitate Call Routing is provided by the Donor Carrier who is required to notify Carriers, via a Ported Local Number Register, that a Port is pending, completed or did not proceed. This relates to all Ports, including Third Party Ports. All participants must use the Ported Local Number Registers to determine the correct Call Routing.

Typically transferred via Web interface:

… a web site that contains a file with a list of Telephone Numbers that have been Ported away from the Donor, or have just returned.

PLNR data is encoded as a fixed-format text file.

What is Re-targeting?

Re-Targeting is a fancy term of changing the date & time.

It’s typically more efficient to re-target a port than withdraw it and resubmit it.

For only two re-targets are allowed for each unique SNA. (Section 4.2.9)

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