Voice Transport is basically just 'nailed-up' voice (with a limited ability to switch). Voice networking is more flexible, using ingress call routing based on dialled numbers to automatically select the optimal path. Both require PORS (Path Oriented Routing System) an NetSynch - the two Nortel proprietary systems used to create fixed-path, jitter-controlled and packet-ordered paths, and ene-to-end synchronisation, respectively. If an intermediate passport in a network has these two things but no "voice" configured (Vroute/SVS, VS, VNCS etc), then it is still capable of "voice transport" - a term that Nortel uses confusingly to apply to the nailed up 'VS' type of voice configuration, rather than the 'Vroute SVS' type which is generally called Voice Networking.
As to your "Network Ring Again" problem, it's probably a signalling channel problem - what sort of signalling are you seeing from your carrier? Voice transport is probably using something like a Common Channel Signalling (CCS) connection which is just being shipped uninterpreted by a Bit Transparent Data Service (BTDS) to the next PABX/PBX. Using Voice Networking, however, you may be trying to decode a proprietary (or at least unsupported by Nortel) feature/signalling. Can you look at debug output from your signalling channel (don't forget to enable debug datastreams to your telnet etc session as well)?
Oh and as a matter of course, ask your local Nortel folks about relevant patches anyway! Good luck...
