Re: Caller Id
Sorry for late reply.
Good info ... BUT ... the sticking point is that you and BT know what the problem is, as you have defined in your comment.
Surely it is possible to have a global directory of Presentation numbers & the transit providers they WILL be routed through.
The routing information gives BT someone to 'aim' at if Presentation numbers are being abused.
My understanding of the issue is that calls from Fake/'borrowed' Presentation numbers are allowed to be routed through the telephone network with no means to 100% VERIFY the authenticity of the call. SIP allows this because you can route whatever you can get away with in the software.
WHY NOT BLOCK CALLS THAT HAVE DUBIOUS PRESENTATION NUMBERS THAT ARE ROUTING FROM UNEXPECTED LOCATIONS. [Hence register idea similar to DNS]
It is a little disingenuous to say 'no way to determine' if you allow dubious Presentation numbers to be routed from a transit provider that they SHOULD not be coming from.
You COULD know what is dubious IF you invested some time in making the whole system more secure by NOT allowing random routing of random Presentation numbers.
You mentioned SIP which can be used/abused to make calls that are not from a 'valid' source yet 'present' as something else.
This is what I meant when saying it being a software issue ... just like anything that connects to the internet ... SIP Gateways can be 'hacked' to 'play' with the calls and what they appear as to the receiving systems.
PABX software can be hacked to 'play' with the calls that are sent/received via a SIP gateway/interface or VOIP in general.
IF you search the interWebs you can find mention of very 'naughty' hacked software that runs on these types devices that can do myriad illegal things. [More than likely something else available on the 'Dark Web']
I am aware of this, I have no background in Telecomms yet it has crossed my path, so I am sure the likes of BT/AT&T etc will be aware.
If the methods/protocols are weak or less secure than is needed they can be improved ... BUT the will and the funds to do so needs to be available & requires ALL Telecom providers to work together.
Saying sorry but doing little to stop it is cheaper !!!
Hence we still have 'scam calls' and have to live with the consequences daily !!!
:)