[regext] RDAP versioning - on client-server interactions and 2-RTT flow

[Pawel Kowalik <[e-mail]>]

Hi,

Thinking of interactions between the client and server that versioning 
draft assumes I think we are heading towards 2-RTT model for every request.

Step 1: The client makes an HTTP GET request to the /help endpoint of 
the RDAP server.
Step 2: The response is processed to extract rdapConformance and versioning.
Step 3: Compare the server's supported extensions and versions with 
those supported by the client.
Step 4: If compatible configurations are found, the client makes target 
request to a resource endpoint (e.g., domain/foo.com) using headers or 
query parameters to specify the desired configuration.

So we have 2 full RTTs. Of course a client can cache it for some time 
but not forever, as the server may change at any time its configuration. 
In a cold state or a client without capability to cache this will be 
always 2-RTT if the client would like to be aware of the versions.

I don't think this is in line with rfc7480, which assumes "a client 
implementation should be possible using common operating system 
scripting tools (e.g., bash and wget)". Also not with the usage pattern 
defined in Section 1. None of it is normative, however I would not just 
ignore it without discussing consequences of going this way.

I would like to see more that versioning draft would assume 1-RTT model 
as a primary use-case, so that the client would put a range of versions 
it supports into a request and the server would put best efforts to 
fulfil it. This would be also more "redirect friendly", so that a 
redirected request to another server (no matter if with query parameters 
or headers) would have the same information about client capabilities 
and able to serve the response as opposed to getting a request for 
configuration crafted for the origin server of a redirect.

Kind Regards,

Pawel