Re: [Netconf] usage of HTTP in restconf-notif-07

[Martin Bjorklund <[e-mail]>]

"Reshad Rahman (rrahman)" <[e-mail]> wrote:
> Hi,
> 
> PSI.
> 
> On 2018-09-17, 1:45 PM, "Netconf on behalf of Martin Bjorklund"
> <[e-mail] on behalf of [e-mail]> wrote:
> 
>     Hi,
>     
>     I think the -07 version is a step in the right direction for this
>     draft.  But I have a comment on the usage of HTTP/2.
>     
>     I am not an expert at all in HTTP/2, but I wonder if the way this
>     draft uses it is correct.  The draft is very short on details, but
>     essentially says that the client POSTs to the "uri" that the server
>     returns (probably w/o a body?), and then that the server sends
>     individual notifications in DATA frames.  Is this really legal?  RFC
>     7540, section 8 says:
>     
>        HTTP/2 is intended to be as compatible as possible with current uses
>        of HTTP.  This means that, from the application perspective, the
>        features of the protocol are largely unchanged.  To achieve this, all
>        request and response semantics are preserved, although the syntax of
>        conveying those semantics has changed.
>     
>     It seems to me that the restconf-notif draft violates this paragraph.
> 
> <RR> Ack, HTTP semantics have to be followed, there's no reason to do
> otherwise. I'll check to see what details/clarifications can be added.
>     
>     In fact, it seems that what the draft tries to do is more or less
>     exactly the same as SSE, except w/o the details, e.g., it doesn't
>     specify the content-type.
>     
>     It also seems to me (after some googling) that it is perfectly fine to
>     use standard SSE with HTTP/2, and that's what people are using to
>     deliver server-generated events/notifs to clients with HTTP/2.
>     
>     So, this draft should probably not mention HTTP/2 at all, but instead
>     just specify the semantics of the "uri" resource and how a client can
>     POST to it to get SSE going.  The draft should the refer to section
>     6.4 of RFC 8040 for how notifications are sent from this resource.
> 
> <RR> My understanding is that HTTP2 is mentioned in the draft so that
> we can use HTTP2 streams. The point you're making is that if this is a
> RESTCONF transport draft then we should just use what's in RFC8040,
> I'm ok with that but would like to hear from the other authors since I
> might be missing some history.

Right.  I think that if HTTP/2 is used then a client can start any
stream it wants; we don't have to specify anything about this in this
draft.  For example, if a client doesn't want to start a new stream,
that should also be ok.


/martin