title: Why does http.sys (before IIS) return badrequest when requests have certain acceptable accept-encoding header values?
body: <p>Given a web app (netcoreapp3.0 hosted in IIS) -- any requests with certain values for Accept-Encoding header never gets to the application.  http.sys parses and spits out a 400 - BadRequest.</p>
  
  <p>i.e., Accept-Encoding: application/gzip,gzip</p>
  
  <p>The issue seems to be the '/' character.</p>
  
  <p>We are not in control of the client(s) and would like to not ask to have them conform/change their client's requests.  Their requests work with other (non IIS) servers.</p>
  
  <p>Unless I'm reading the <a href="https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3" rel="nofollow noreferrer">spec</a> incorrectly -- I believe the above value is valid for the header.
  Thought about asking or reporting a bug in github - dotnet/aspnetcore - but not sure if it's a bug.</p>
  
  <p>Thanks for any advice.</p>
  
  <p>Would like to avoid a Kestrel w/ apache | nginx reverse proxy.</p>