Clarified handling of the Reply-From Option on the client side

Author: marco-tiloca-sics

draft-ietf-core-groupcomm-proxy.md

@@ -394,7 +394,7 @@ The example in this section refers to the following actors.
 
 * Two origin servers S1 and S2, where the server Sx has address Sx_ADDR and port number Sx_PORT.
 
-The origin servers are members of a CoAP group with IP multicast address G_ADDR and port number G_PORT. Also, the origin servers are members of the same application group and share the same resource /r.
+The origin servers are members of a CoAP group with IP multicast address G_ADDR and port number G_PORT. Also, the origin servers are members of the same application group and share the same resource at /r.
 
 The communication between C and P is based on CoAP over UDP, as per {{RFC7252}}. The communication between P and the origin servers is based on CoAP over UDP and IP multicast, as per {{I-D.ietf-core-groupcomm-bis}}.
 
@@ -482,7 +482,7 @@ The proxy processes the CoAP responses forwarded back to the client as defined i
 
   * The CRI that is present as the first element of the CBOR sequence specifies an addressing information TARGET_1, such that a unicast request reaches the proxy if it is sent according to TARGET_1.
 
-  * A CRI reference MUST be present as the second element of the CBOR sequence in case, upon receiving a unicast request that has been sent according to TARGET_1, the proxy forwards the request based on what is specified by the Uri-Host, Uri-Port, and Uri-Path Options included in the request. The CRI reference specifies the same information that the proxy expects to be specified in the Uri-Host, Uri-Port, and Uri-Path Options of such a unicast request.
+  * A CRI reference MUST be present as the second element of the CBOR sequence in case, upon receiving a unicast request that has been sent according to TARGET_1, the proxy forwards the request based on further information than TARGET_1 and relying on what is specified by the Uri-Host, Uri-Port, and Uri-Path Options included in the request. The CRI reference specifies the same information that the proxy expects to be specified in the Uri-Host, Uri-Port, and Uri-Path Options of such a unicast request.
 
     Otherwise, the second element of the CBOR sequence MUST NOT be present, in which case the proxy forwards the unicast request solely based on the addressing information TARGET_1 according to which the request has been sent to.
 
@@ -508,7 +508,11 @@ The client processes the CoAP responses forwarded back by the proxy as defined i
 
    Effectively, the client sends the unicast request either directly to the origin server (in case the proxy stands in only for the whole group of servers, but not for the individual servers in the group), or to the proxy (in case the proxy stands in for both the whole group of servers and the individual servers in the group).
 
-   In case the value of the Reply-From Option specifies also a CRI reference as the second element of the CBOR sequence, then the client includes the Uri-Host, Uri-Port, and Uri-Path Options in the unicast request, according to what is specified by the corresponding elements of the CRI reference. If the client wants to specify additional path segments that identify a specific resource at the origin server, then the corresponding Uri-Path Options are included in the request after the Uri-Path Options corresponding to the path component of the CRI reference.
+   In case the value of the Reply-From Option specifies also a CRI reference as the second element of the CBOR sequence, then the client includes the Uri-Host, Uri-Port, and Uri-Path Options in the unicast request, according to what is specified by the corresponding elements of the CRI reference. In particular:
+
+   * If 'authority' is given in the CRI reference and it does not include 'port', then the client MUST NOT include the Uri-Port Option in the unicast request.
+
+   * If the client wants to specify additional path segments that identify a specific resource at the origin server, then the corresponding Uri-Path Options are included in the request after the Uri-Path Options corresponding to the path component of the CRI reference.
 
 # Caching # {#sec-proxy-caching}
 
@@ -1494,6 +1498,8 @@ C                               P                      S1           S2
 
 * Updated references.
 
+* Clarified handling of the Reply-From Option on the client side.
+
 * Extended security considerations on client authentication.
 
 * Clarifications and editorial improvements.