05 PSTN connectivity

• One user places a call with one connectivity option. The tenant may mix Calling Plan, Operator Connect, Teams Phone Mobile, and Direct Routing.

• Direct Routing signaling uses TLS to the Teams SIP proxies on TCP 5061. The SBC FQDN must be in the certificate SAN.

• Media bypass can send RTP between the client and the SBC. Signaling stays with Teams.

Facts in the long lessons were checked 14 October 2026. This sheet is a memory aid.

Sources and go deeper

PSTN connectivity options — Microsoft Learn — last checked 2026-10.
Plan Direct Routing — Microsoft Learn — last checked 2026-10.
RFC 3261 — RFC — last checked 2026-10.
Public switched telephone network — Wikipedia — last checked 2026-10. Wikipedia fallback for background. Confirm the vendor page before you change a tenant
Session Initiation Protocol — Wikipedia — last checked 2026-10. Wikipedia fallback for background. Confirm the vendor page before you change a tenant
Microsoft Teams blog index — Community — last checked 2026-10. Community index for the Microsoft Teams blog. This is the index, not a claim that a post discusses this room
Calling Plans — Microsoft Learn — last checked 2026-10.
Emergency locations, addresses, and routing — Microsoft Learn — last checked 2026-10.
Plan Operator Connect — Microsoft Learn — last checked 2026-10.
Plan Teams Phone Mobile — confirm — last checked 2026-10. Did not open when checked. HTTP 404.
Plan for Teams Phone Mobile - Microsoft Teams | Microsoft Learn — Microsoft Learn — last checked 2026-10. Opened in place of a page that did not open when checked. This is the page that opened, not proof it equals the old slug
Certified SBCs for Direct Routing — Microsoft Learn — last checked 2026-10.