Hi David, this is the OPS-DIR review. I tried to stay in my lane.

I found this paragraph confusing (which doesn't mean it is incorrect, just that someone with limited background read the section 2 requirements list, all MUSTs, and then the paragraph below, which seems to have a conflicting MUST with the SHOULD and MAY that follows). Help readers like me understand the options you are allowing here:

   If the client detects that any of the requirements above are not met
   by a URI Template, the client MUST reject its configuration and fail
   the request without sending it to the UDP proxy.  While clients
   SHOULD validate the requirements above, some clients MAY use a
   general-purpose URI Template implementation that lacks this specific
   validation.

I see that Christer's GEN_ART review picked-up on this too (I looked after I was done...).

In Section 5, there seems to be a possible operations issue for proxy operators:

   Clients MAY optimistically start sending UDP packets in HTTP
   Datagrams before receiving the response to its UDP proxying request.
   However, implementors should note that such proxied packets may not
   be processed by the UDP proxy if it responds to the request with a
   failure, or if the proxied packets are received by the UDP proxy
   before the request.
This seems like a good place to limit the amount of optimistic traffic, given that the request is not yet accepted. (also, would the optimistic traffic use Context ID zero?)

In
6.  Performance Considerations
   UDP proxies SHOULD strive to avoid increasing burstiness of UDP
   traffic: they SHOULD NOT queue packets in order to increase batching.  

This requirement is written qualitatively, so users might "know a violation if they see it", but not hold the proxy system/operator to any specific performance without providing more details here. Inter-packet delay variation measurements on proxy ingress and egress would characterize increased burstiness well.  Another solution is s/SHOULD/should/ (I doubt some increased burstiness will be avoidable, or enforceable.)

Thanks in advance for considering these comments,
Al