This is a question I get asked again and again
There three federation levels are:
- Direct Federation the access edge FQDN is manually entered with the sip domain on the federation allowed domain list rather than using SRV records thus bypassing the requirement for the server FQDN to match the sip domain FQDN and minimising on certificate requirements. (Think of this as ‘Allow Partner Server’)
- Open Federation is limited to use 1000 SIP URI’s and 20 messages per second, typically in anything other than a small environment enhanced federation has to be used by adding the sip domain to list of allowed domains to bypassing these limits. (Think of this as ‘Discovered Partners’)
- Enhanced Federation as above enhanced domains in the watch list then these are added to the allow list in the Lync Control Panel (Think of this as ‘Allow Partner Domain’)
