Using a filetransfer on version 21.0 with the agents being on 21.0 and 12.x throws an error:
Release : 12.3
The TLS Gateway agent is required for filetransfers between TLS enabled agents (most 21.0 agents) and non-TLS enabled agents (12.x agents and a handful of 21.0 agents listed here). This is to ensure security with filetransfers between GSS (non-TLS enabled) and TLS-enabled agents. There's a good video on this here: https://www.youtube.com/watch?v=j4w_snNyRu8
Version 12.x agents in a filetransfer with 21.x agents must use the TLS Gateway to allow for transferring.
Version 12.x agents transferring with 12.x agents can connect to the system via a CP and not the TLS Gateway. The CP referred to here is the standard CP or ucsrvcp process that was in 12.x as well.
Is there another way to enable file transfers without using the TLS Gateway?
The following are the only available ways to run filetransfers when the AE is on 21.0:
TLS-enabled agent <-> TLS-enabled agent
TLS-enabled Agent <-> TLS Gateway <-> Non-TLS-enabled agent
Non-TLS-enabled Agent <-> Non-TLS-enabled agent
There is no way around this in version 21.0; the current 21.0 Non-TLS-enabled agents are planned to be moved to being TLS in future released, but we don't currently have timeline for this.