VW-TP (Transport Protocol) is the correct term. CAN-Bus, like Ethernet or RS232, is only responsible for the hardware-based transmission. The Golf IV has TP1.6, while the Golf V/Touran has TP2.0. The Passat 3B/BG has TP1.6, and from the Passat 3C onwards, it uses TP2.0. It's roughly possible to determine the timeframe during which the change occurred, although exceptions tend to confirm the rule.
Information is not freely available. Everything is "non-disclosure." Those interested in this topic simply monitor the traffic and try to decipher it themselves. One resource, besides Google, would be
CanHack Forum. You can also check out
OSEK/VDX, specifically the specifications for NM and COM. This is very similar to the VW-TP and gives you an idea of what to expect. Another source of information is Bosch's MC-Net, which is very similar to VW-TP1.6. About two years ago, it could still be ordered for free from Vector Informatik. I believe that the link I'm referring to has been removed from your website.
It's also important to note that transport protocols will likely be of limited use to you, as they primarily deal with the transfer of data volumes. Essentially, it involves breaking down data into 7-byte blocks, reassembling them later, performing error checking, and retrying if necessary.
What's interesting are the usage data, which are not part of the TP specifications, but which can vary from model to model – although they are generally quite similar. Here, the only thing that helps is - snorting
Regards,
Axel.