The major difference between all previous releases and 6.0 is that VxWorks is no longer the base language for the software. At 6.0 Nortel has migrated to the LinUx (Redhat) baseware. The LinUx basware enables running the CallServer as an application on the LinUx baseware. Plus it is SIP enabled, to provide multimedia desktop integration. The elimination of the ISP1100 Sig Server (Replaced by COTS server or CPPM in the cabinet. The other major difference is the migration to a "Security Domain" to provide single sign-on authentication using UCM (Unified Communication Manager - replaces TM). UCM installs as an application on the Security domain server as part of the LinUx base installation.
The other significant change, since you are now in a new platform and OS, is the tangible migration away from CLI. In UCM you can even build phones using point and click, similar to TM/OTM. Zone based dialing has been added to the mix, as an option for large enterprise customers. CLI is still available via the EM interface as a "Virtual Terminal" for die-hard techs, but you have to login using UCM credentials after installing the system and initializing, then you have to type cslogin, followed by the local credentials for that system. i.e. admin1.
Any questions?
EOM