3 ms·

This is a bit off-topic but I'm wondering if I'm going to have to hack baresip to implement it: Is there such thing as a SIP to mobile phone bridge, so that yo

This is a bit off-topic but I'm wondering if I'm going to have to hack baresip to implement it: Is there such thing as a SIP to mobile phone bridge, so that you can make phone calls over the net via a mobile phone that is in some remote location? The application in my case is making local calls in a country that is expensive to call into. If it exists its the kind of thing that is resistant to search, unless it's called something I'm not aware of. Edit: I think I might be looking for a SIP GSM Gateway running on an Android phone To clarify I'm looking for: initiate voip handset call => internet => call is initiated from remote mobile phone remote mobile phone receives call => internet => voip handset rings Or put another way something that exposes the Android phone as a trunk line.

jshreder 3y ago
You can try a software PBX solution -- I've spun up quite a few 3CX deployments using Twilio as the SIP provider. Then you can call in a number of ways (super configurable routing inbound and outbound). There's a "softphone" mobile app for internet -> sip calling on smart phones. 3CX has pretty reasonable licensing (I think there may still be a free tier) and Twilio is super cheap.
somat 3y ago
I am using baresip on my phone(from fdroid). I don't have my whole stack plumbed yet so I can't say how well it works. but it connects to my asterisk server via wifi well enough. I was expecting sip to be built into android but apparently it was removed in 10 or 11. but found the baresip package. I like baresip well enough for desktop use so I decided to try it on the phone. It is one of those slow burn projects I work on every couple of months. mainly because I hate doing anything on the phone. but the idea is I have an asterisk server at the office that ties into the dialed phone world via sip trunk. I should be able to put a sip client on the phone, tunnel a secure connection to the office then the cell phone is just another office phone... anywhere in the world. Only piece left is the tunnel, I have my heart set on ipsec. is this folly? should I be looking into other tunnel tech?
- mgsouth 3y ago
  ipsec for the control plane (SIP) might be OK, but you'll probably run into jitter and latency issues with the media (RTP/RTCP). Also RTP has provisions for packet loss, but end-to-end encryption won't like that. SIP already has an encrypted mode [1], but I don't know how well it's currently supported in the wild. The purpose-built secure media protocols are Secure RTP/Secure RTCP [2]. Getting just plain SIP and RTP through consumer, enterprise, and cell carrier nets can be troublesome. For example, SIP especially is NAT-antagonistic, and edge routers can try to be "helpful" and do half-baked proxying or deep packet mangling that just messes up your smarter VoIP server. Consumer ISPs have a tendency to block SIP altogether. Throwing in encryption complications may give you another layer of hard-to-diagnose headaches. (Of course, if you can get the secure layer through the net it might force intermediaries to keep their fingers out. Other tricks like using non-standard ports can help with that, too.) Source: used to run the signalling/media dev team for a VoIP provder many moons ago, but we didn't bother with the secure modes/protocols. [1] https://en.wikipedia.org/wiki/Session_Initiation_Protocol#Encryption https://en.wikipedia.org/wiki/Session_Initiation_Protocol#En... [2] https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Protocol https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Pro...
- flas9sd 3y ago
  VoWifi is using an ipsec tunnel for both SIP/RTP to the providers IMS stack. With its popularity I think it's likely network admins increasingly allow for it in networks you do not control.
jjrh 3y ago
There are sip gsm gateways. Some that can take 16+ sims. Take a look on AliExpress.

jshreder 3y ago

You can try a software PBX solution -- I've spun up quite a few 3CX deployments using Twilio as the SIP provider. Then you can call in a number of ways (super configurable routing inbound and outbound). There's a "softphone" mobile app for internet -> sip calling on smart phones. 3CX has pretty reasonable licensing (I think there may still be a free tier) and Twilio is super cheap.

somat 3y ago

I am using baresip on my phone(from fdroid). I don't have my whole stack plumbed yet so I can't say how well it works. but it connects to my asterisk server via wifi well enough. I was expecting sip to be built into android but apparently it was removed in 10 or 11. but found the baresip package. I like baresip well enough for desktop use so I decided to try it on the phone. It is one of those slow burn projects I work on every couple of months. mainly because I hate doing anything on the phone. but the idea is I have an asterisk server at the office that ties into the dialed phone world via sip trunk. I should be able to put a sip client on the phone, tunnel a secure connection to the office then the cell phone is just another office phone... anywhere in the world. Only piece left is the tunnel, I have my heart set on ipsec. is this folly? should I be looking into other tunnel tech?

mgsouth 3y ago
ipsec for the control plane (SIP) might be OK, but you'll probably run into jitter and latency issues with the media (RTP/RTCP). Also RTP has provisions for packet loss, but end-to-end encryption won't like that. SIP already has an encrypted mode [1], but I don't know how well it's currently supported in the wild. The purpose-built secure media protocols are Secure RTP/Secure RTCP [2]. Getting just plain SIP and RTP through consumer, enterprise, and cell carrier nets can be troublesome. For example, SIP especially is NAT-antagonistic, and edge routers can try to be "helpful" and do half-baked proxying or deep packet mangling that just messes up your smarter VoIP server. Consumer ISPs have a tendency to block SIP altogether. Throwing in encryption complications may give you another layer of hard-to-diagnose headaches. (Of course, if you can get the secure layer through the net it might force intermediaries to keep their fingers out. Other tricks like using non-standard ports can help with that, too.) Source: used to run the signalling/media dev team for a VoIP provder many moons ago, but we didn't bother with the secure modes/protocols. [1] https://en.wikipedia.org/wiki/Session_Initiation_Protocol#Encryption https://en.wikipedia.org/wiki/Session_Initiation_Protocol#En... [2] https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Protocol https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Pro...
flas9sd 3y ago
VoWifi is using an ipsec tunnel for both SIP/RTP to the providers IMS stack. With its popularity I think it's likely network admins increasingly allow for it in networks you do not control.

jjrh 3y ago

There are sip gsm gateways. Some that can take 16+ sims. Take a look on AliExpress.