I am planning a Teams direct routing solution for a client who's tenant is located in Europe. This will be the first site for PSTN services via direct route which will be supporting 100 or so staff in Australia. My understanding direct routing is that the SBC will establish a trunk by resolving to sip.pstnhub.microsoft.com, sip2.pstnhub.microsoft.com and sip3.pstnhub.microsoft.com which should return an IP of the closest edge to the location of the SBC.
Are there any other considerations required when providing PSTN to sites that are in a different global region to the primary tenant?
sip.pstnhub.microsoft.com is a Global FQDN will make sure that your SBC is always connecting to the closest datacenter. So for a SBC in Europe connecting to sip.pstnhub.microsoft.com will be connected to Microsoft datacenter in Europe and sip2.pstnhub.microsoft.com will connecting to a datacenter in USA.
If possible you should place a SBC in Australia, then you will be able to use Media bypass (when released) so that media traffic goes from a user to SBC and directly to your SIP trunk. You can also use Calling Plans in Australia if you don't want to place a SBC there.
For other locations you should check if there is any local regulations, like local breakout for emergency numers (112, 911, 000). Some countries have regulations so you are not allowed to send out PSTN calls on IP connections.
Best Response confirmed by
Jason Childs (Occasional Contributor)