Re: [core] RFC 7252 - Forward Proxies

[Achim Kraus <[e-mail]>]

Hi Klaus,

thanks again for the clarifications!

best regards
Achim

Am 11.01.20 um 14:03 schrieb Klaus Hartke:
> 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
>