warn against mixing with other multiplexers (Closes #2)

draft-dkg-dprive-demux-dns-http.md

@@ -33,6 +33,14 @@ informative:
  RFC7830:
  RFC7858:
  I-D.ietf-dnsop-dns-wireformat-http:
+ HAPROXY:
+    target: https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt
+    title: The Proxy protocol
+    author:
+      name: Willy Tarreau
+      ins: W. Tarreau
+      org: HAProxy Technologies
+    date: 2017-03-10
 normative:
  RFC1035:
  RFC1945:
@@ -144,6 +152,19 @@ fail or trigger other "interesting" behaviors.  This approach should
 be done only in channels sufficiently obscured that a transparent
 proxy would not try to interpret the resultant stream.
 
+Avoid mixing with other demultiplexing
+--------------------------------------
+
+Some other (non-IETF) systems (e.g. {{HAPROXY}}) take a similar
+approach with multiplexing data on top of HTTP by taking advantage of
+bitpatterns that are presumed to not be present in normal HTTP
+requests.
+
+Use of the approach described in this draft in conjunction with these
+other approaches is not advisable.  Doing so safely would require
+explicit and detailed review of all three (or more) protocols
+involved.
+
 Why not ALPN?
 -------------