Title: Delta xDS protocol question re: requests in flight

Description:

After a read of the xDS protocol docs, I have a couple of questions centering around the implementation of delta xDS:

• According to this doc, it seems like the delta protocol (at least as of v1.14.1) is only implemented for CDS, is this in fact the case? If not, what resource types are supported as of v1.14.1?

• Are there any guarantees about the number of requests in flight from the client? i.e., can I assume that a client won't make two successive requests on the same stream for the same resource type without acking previous requests first? The reason I ask is if this is indeed the case, it will make the logic for streaming much easier.

Thanks a bunch!