Redirecting SIP calls from another SIP server to Teams user

[Pradeep_Patil]

I am trying to understand if SIP calls can be transferred/redirected from a another/thirdparty SIP server to a Microsoft Teams user.

I was reading below links:

https://docs.microsoft.com/en-us/microsoftteams/direct-routing-protocols-sip

https://docs.microsoft.com/en-us/microsoftteams/sip-gateway-plan

https://docs.microsoft.com/en-us/microsoftteams/direct-routing-plan

As per my understanding we need to use Direct routing, and for direct routing Microsoft certified SBC need to be configured along with the SIP proxy.

But if we have the URL for the Microsoft Teams SIP Endpoint and the credentials to access it, can we transfer calls from another SIP server by configuring the URL and credentials? Will it work or is this supported?

I have below questions:

1. Can we transfer the SIP calls from another SIP server to Microsoft Teams user?

2. If it is possible what are the available ways of achieving this?

3. Do we need to have SBC configured for having this functionality, is it must?

4. Is there a document which explains this process step by step?

[#2]

@Pradeep_Patil - Are you developing any Teams application?
If yes, could you please elaborate more on it.

[#3]

I have the same question. I need to interconnect a 3rd party cloud PBX to Teams. Does Teams support incoming SIP calls from external SIP servers?

[#4]

@StevieG1966 

looking at this article, Microsoft Teams call flows - Microsoft Teams | Microsoft Learn 

I see this, which makes me think that direct SIP calls into Teams are not supported.  I am I reading this correctly?

Interoperability restrictions

Third-party media relays. A Teams media flow (that is, where one of the media endpoints is Teams) may traverse only Teams or Skype for Business native media relays. Interoperability with a third-party media relay is not supported. (Note that a third-party SBC on the boundary with PSTN must terminate RTP/RTCP stream, secured using SRTP, and not relay it to the next hop.)

Third-party SIP proxy servers. A Teams signaling SIP dialog with a third-party SBC and/or gateway may traverse Teams or Skype for Business native SIP proxies. Interoperability with a third-party SIP proxy is not supported.

Third-party B2BUA (or SBC). A Teams media flow to and from the PSTN is terminated by a third-party SBC. However, interoperability with a third-party SBC within the Teams network (where a third-party SBC mediates two Teams or Skype for Business endpoints) is not supported.