You need a public certificate for your SBCs to communicate with Microsoft Teams. This is because encrypting signalling and media traffic over the internet is important to prevent eves dropping / wire tapping.
You can obtain certificates from any of the common signing authorities e.g. GoDaddy, GlobalSign etc. But the SBC must have both the public and private key of the certificate installed.
You can have one of three certificate types
- Single Domain SSL – this must be the public FQDN of the SBC the certificate will be installed on
- SAN Certificate – useful for multiple SBC deployments – each SBC FQDN must be a SAN on the certificate
- Wildcard Certificate – useful for cost savings in multiple SBC deployments
The maximum supported key length is currently 2048 bits.