[LINK] Ported telephone numbers

[Paul Brooks]

On 10/01/2018 4:12 PM, David wrote:
> On Wednesday, 10 January 2018 2:34:20 PM AEDT Paul Brooks wrote:
>
>> All of these [voice transport protocols] are part of the PSTN, and the traditional telephone number addressing is the Universal Voice Glue that makes it all work together relatively seamlessly, and lets someone on a POTS line call someone on IP line without having to be aware of what technology the receiver is using at that moment. Not quite irrelevant!.
> However IP-based voice connections will be in a huge majority when the NBN finishes its rollout, probably enough to warrant a strategic rethink.  Call routing based on POTS number, as currently done by the carriers, logically duplicates a function which could, in principle, be done by the IP (i.e. NBN) network.  Surely it should be possible to integrate the IP and remaining POTS networks so the whole system is more efficient and way less cumbersome.
I think what you're looking for is RFC 6116 ENUM - a DNS lookup of a telephone number
to a URI such as a SIP address, and RFC 5067, RFC 5526 "Infrastructure ENUM", and RFC
3824 "Using E.164 number with SIP".

Check https://en.wikipedia.org/wiki/Telephone_number_mapping for an overview.

However, having a lot of IP-based access lines is not the same as having a world, or
even a country, where everybody can be interconnected end-to-end with a VoIP call.

Considerations like lawful interception, metadata retention etc require the call to
pass through the RSPs on the way through, it can't just take a shorter routing path
direct IP-to-IP or neighbour-to-neighbour like nirvana of IP telephony might imagine,
as it might occur within a single campus like a corporate office, so there's little
real routing efficiency to be gained.

Sure routing by POTS number duplicates a function that IP networks could do, for calls
to another IP line - but the telephone service transcends IP and exists above IP, in
an application layer, and needs to work across all the other technologies as well - so
it should use an addressing and routing system appropriate to its layer, not be
limited by the shoehorning it into a lower layer. ENUM is the translation method from
one to the other.  The reality is that a large number of calls to and from an
IP-enable voice line won't have another IP-enabled voice line at the other end,
they'll hit a gateway in the middle. Incoming calls from international locations,
corporate offices and call centres (generally on ISDN-PRI-based PABXs ), mobile
networks and conventional POTS lines will all still need to use a E.164 telephone
number to reach the consumer.

>From the consumer making an outbound call, its still actually easier and quicker to
punch in a telephone number than to tap out a long SIP URI, and devices need a much
smaller keypad too, and for those using a directory where they select a name or a face
(like a mobile handset contacts directory) it doesn't really matter if the underlying
entry for the picture is a number or a SIP URI. So from a usability perspective, the
conventional telephone number is still actually easier to use.

(Also, re the NBN - The NBN is an Ethernet Layer 2 network, not an IP network, and
consists of 121 disconnected islands rather than a national network, so national VoIP
interconnection can't and shouldn't be done within the NBN anyway!)

cheers,
    Paul.


 




>
>
>>> I see, I'd assumed the mandatory requirement to publish a PLNR ("Ported Local Number Register") file was intended to allow all carriers to route calls directly to the carrier currently holding a ported number without going through the donor carrier.  But the whole idea might be suffering scability problems now.
>> That is the idea - but also, even interconnect arrangements are bilateral as well.  'Your' carrier may not even have a bilateral network interconnect directly with the final destination network hosting the number, and may have to route the call through a third network who will provide the transit connectivity (who might or might not be the original donor carrier) - who will do a second lookup of the PLNR in the process to work out which direction to forward the call to.
> Out of interest I downloaded the full "EnhancedFullDownload.csv" file (81.4 Mbytes!) from
> https://www.thenumberingsystem.com.au/#/number-register/search  This shows the allocated and current holders of the entire POTS numbering range, but at a quick look I couldn't see any individual numbers, just ranges.
>
> It's all something of a mystery, I suppose there's probably a degree of ad-hocery going on...
>
> David L.
>