Re: Analogue to Digital Voice issues

From	David Woolley <david@ex.djwhome.demon.invalid>
Newsgroups	uk.telecom
Subject	Re: Analogue to Digital Voice issues
Date	2026-05-22 11:46 +0100
Organization	No affiliation
Message-ID	<10upc61$1dh4e$1@dont-email.me> (permalink)
References	<10ul8vf$38ia$1@dont-email.me> <n77nneFlpidU1@mid.individual.net> <10umb58$i3t0$1@dont-email.me> <n77s9cFmevqU1@mid.individual.net> <4Qv*VD7GA@news.chiark.greenend.org.uk>

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On 21/05/2026 11:26, Theo wrote:
> Your router keeps registered with your ISP's SIP server.  I'm not sure
> there's VLANs involved, at least for some ISPs you can connect over the
> internet if you can find out the login details (which they try to hide from
> you).  

This only applies to ISPs like BT retail, who provide a combined 
service.  Some ISPs don't provide telephony and some sell their ITSP and 
ISP services as different, and separable, products, so you can use the 
telephony over any other ISP, who doesn't block the ports used.  The 
sort of provider that sells independent products doesn't lock down the 
login credentials.

BT use a VLAN to carry the PPP over Ethernet for their combined voice 
service, and distinguish it from the PPP over Ethernet for the internet 
service.  I think it would be theoretically possible to use their voice 
service with a different head end internet service provider.

With providers that provide ITSP services separately, the SIP user agent 
need not be part of the router, or you could have one in the router, and 
also direct IP connections to other ones.  They would use the same PPP 
over Ethernet connection for both internet and telephone.

> 
> The ISP server looks up the number in the database, finds which client it
> needs to talk to.  It sends a message to the SIP client in your router

Pet peeve.  It sends it to the SIP server in the router.  It might be 
technically valid to say a VoIP client, but SIP is a symmetric protocol, 
unlike analogue telephony, and the side initiating the call is the SIP 
Client User Agent (UAC), and the side receiving it is the SIP Server 
User Agent (UAS), so once one introduces SIP, one should align with the 
SIP usage of client and server. (Actually, it is possible for UAS and 
UAC client roles to switch during a call.)

Thread

Analogue to Digital Voice issues Jeff Layman <Jeff@invalid.invalid> - 2026-05-20 22:27 +0100
  Re: Analogue to Digital Voice issues Andy Burns <usenet@andyburns.uk> - 2026-05-21 07:40 +0100
    Re: Analogue to Digital Voice issues Jeff Layman <Jeff@invalid.invalid> - 2026-05-21 08:10 +0100
      Re: Analogue to Digital Voice issues Andy Burns <usenet@andyburns.uk> - 2026-05-21 08:58 +0100
        Re: Analogue to Digital Voice issues Theo <theom+news@chiark.greenend.org.uk> - 2026-05-21 11:26 +0100
          Re: Analogue to Digital Voice issues David Woolley <david@ex.djwhome.demon.invalid> - 2026-05-22 11:46 +0100
  Re: Analogue to Digital Voice issues Richmond <dnomhcir@gmx.com> - 2026-05-21 09:11 +0100
  Re: Analogue to Digital Voice issues Nick Finnigan <nix@genie.co.uk> - 2026-05-21 10:27 +0100
    Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-21 10:37 +0100
      Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-23 12:13 +0100
        Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-23 12:44 +0100
          Re: Analogue to Digital Voice issues "J. P. Gilliver" <G6JPG@255soft.uk> - 2026-05-23 20:29 +0100
          Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-24 10:42 +0100
            Re: Analogue to Digital Voice issues Jeff Layman <Jeff@invalid.invalid> - 2026-05-24 11:30 +0100
              Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-24 13:36 +0100
                Re: Analogue to Digital Voice issues Jeff Layman <Jeff@invalid.invalid> - 2026-05-24 15:24 +0100
                Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-24 16:41 +0100
                Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-25 10:26 +0100
                Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-25 11:29 +0100
                Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-26 09:13 +0100
              Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-25 10:28 +0100
                Re: Analogue to Digital Voice issues Jeff Layman <Jeff@invalid.invalid> - 2026-05-25 12:35 +0100
                Re: Analogue to Digital Voice issues David Wade <g4ugm@dave.invalid> - 2026-05-25 17:45 +0100
                Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-26 09:16 +0100
                Re: Analogue to Digital Voice issues Trolleybus <ken@birchanger.com> - 2026-05-26 09:15 +0100
  Re: Analogue to Digital Voice issues David Wade <g4ugm@dave.invalid> - 2026-05-21 19:08 +0100
    Re: Analogue to Digital Voice issues Davey <davey@example.invalid> - 2026-05-21 20:04 +0100
      Re: Analogue to Digital Voice issues grinch <grinch@somewhere.net> - 2026-05-22 10:26 +0100

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