Re: [core] RFC 7252 - Forward Proxies

[Klaus Hartke <[e-mail]>]

Achim Kraus wrote:
> In my understanding the, CoAP URI-Host option will be "example.com" and
> not "198.51.100.1", otherwise hosts with multiple virtual server will
> not be able to differentiate the logical request destination.

Oh, sorry. I changed the example at some point from "example.com" to
"198.51.100.1" and apparently didn't change all instances. Here's the
corrected example:

   If a client wants to GET a representation of
   <coap://198.51.100.1:12345/.well-known/core>,
   then the CoAP options always encode
   <coap://198.51.100.1:12345/.well-known/core>,
   regardless of the destination of the UDP datagram.

Of course, the same is true for "example.com":

   If a client wants to GET a representation of
   <coap://example.com:12345/.well-known/core>,
   then the CoAP options always encode
   <coap://example:12345/.well-known/core>,
   regardless of the destination of the UDP datagram.

> Also in my understanding, the port, IP-literal and IPv4address (the none
> regname variants), are only included, if they differ from the
> destination (which will be the porxy's address in case of a proxy).

Yes, exactly. In pseudo-code:

  |url| = the request URI
  |scheme| = the <scheme> component of |url|
  |host| = the <host> component of |url|
  if the <port> component of |url| is present then
    |port| = the <port> component of |url|
  else
    |port| = the default port number for |scheme|
  endif

  if a forward-proxy is configured then
    include a Proxy-Scheme option with value |scheme|
    |transfer-protocol| = the protocol of the forward proxy
    |destination-host| = the IP address of the forward proxy
    |destination-port| = the port number of the forward proxy
  else
    do not include a Proxy-Scheme option
    |transfer-protocol| = the protocol indicated by |scheme|
    |destination-host| = |host| resolved to an IP address
    |destination-port| = |port|
  endif

  if |host| equals |destination-host| then
    do not include a Uri-Host option
  else
    include a Uri-Host option with value |host|
  endif

  if |port| equals |destination-port| then
    do not include a Uri-Port option
  else
    include a Uri-Port option with value |port|
  endif

(Necessary data conversions omitted for brevity.)

>  > It's the port number of the request URI (or, if the port number in
> the request URI is omitted, the default port number for the scheme of
> the request URI). It's not the port number of the forward proxy.
>
> My question was rather, if it's the default port of the proxy scheme
> (maybe http), or the requests coap-uri-scheme.

It's the default port number for the scheme of the request URI.


Klaus