2024-08-15

Cool feature on VoLTE

Our SIP2SIM SIMs run through ONSIM/Tango, and uses VoLTE normally. OK a lot of acronyms, I know.

The key point is we feed the call to the mobile network using SIP.

SIP allows the calling number to be set with a number (well, technically anything in the local part of the sip address) and a name.

Eg. I could have From: "Adrian" <sip:401@whatever>

On my SIP phone on my desk it shows both Adrian and 401, which is great. It has options to show one or the other or both.

I use this feature in our call routing, so, for example, if someone calls my 02000 number, I prefix the name part with a 2, and then the calling number. Similarly if someone calls my 0800 number I prefix it with 080. That way, even if all I can see is the name part, I get to see the calling number and a prefix indicating which of my numbers was originally called. In hindsight I may make the 0800 just have 8 as 080 then 0 looks even more confusing at first.

For example, this call:

As you see, the name part is 0800759...

What I have noticed is that the name part gets all the way to my mobile (iPhone).

I know this because of the missed call list.

Sadly when the call comes in, the main phone screen only shows the CLI, not the name part, which is a shame. Though on my Mac (which also shows the incoming call) it shows both.

It would be nice to have an option to show name, or both.

P.S. I cannot tinker with the actual CLI due to OFCOM rules - it has to be a plausible number. The fact the name gets through gives some hope of handling better local / internal CLI using Name field.

7 comments:

  1. Having the name come through is really nice. All we need now is for the world to move on from G.711 and start using wideband codecs.

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  2. Nice feature.

    Trying to replicate this myself using the Tag: field in clueless works for me to prefix the name shown on iPhone - however actual CLI (over ONSIM - desk phone is correct) is mangled and shows as +1 (1) (473)... for what should be +44 7473...

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  3. Your short CLI would not get through, which is why it is mangled. I believe we document it. Ofcom rules stopped us sending meaningful CLIs for internal calls, sadly.

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    Replies
    1. My 'short' CLI is only shortened for redacting it here. A bit clearer: CLI shows as +1 (1) (473)xxxxxx for what should be +44 7473xxxxxx. I was surprised that this wasn't passed through.

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    2. OK I am puzzled, we will normally only do the +1(1) thing for something that looks like an invalid CLI, can you email support with details of the call time and number so we can check the logic.

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    3. On further investigation I think this explains what's happening as I am calling myself to test this out:
      "Unfortunately it also seems that a CLI that matches the number we have assigned to the SIM always reports as Busy even when the handset is not busy, so this two [too?] gets replaced in the same way." https://www.aa.net.uk/voice-and-mobile/sip2sim/technical/

      Delete
    4. Typo fixed, I suspect that may be the case. Stupid, I know, and nothing we can do sadly.

      Delete

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