Re: [netconf] Magnus Westerlund's No Objection on draft-ietf-netconf-restconf-notif-13: (with COMMENT)

["Reshad Rahman (rrahman)" <[e-mail]>]

Hi,

On 2019-05-23, 4:00 AM, "Magnus Westerlund" <[e-mail]> wrote:

    Hi,
    
    
    >
    >     >
    >     >        o  take any existing subscription "dependency", as specified by 
    > the
    >     >           "dependency" leaf node in
    >     >           [I-D.draft-ietf-netconf-subscribed-notifications], and use 
    > the
    >     >           HTTP2 stream for the parent subscription as the HTTP2 stream
    >     >           dependency, [RFC7540] section 5.3.1, of the dependent
    >     >           subscription.
    >     >
    >     >     What is not obivous to me is that just because that a subscription 
    > exists
    > at
    >     >     the publisher that it is going over the same HTTP/2 connection and 
    > thus
    > there
    >     >     might be nothing for the dependency to point at that is relevant 
    > for the
    >     >     mechanism described in RFC 7540. I didn't even find a 
    > recommendation
    > that the
    >     >     receiver (subscriber) should actually re-use the HTTP/2 connection 
    > for
    > all
    >     >     communication with the same publisher.
    >     >  <RR> Good point, this is not spelled out.  We will add text for the
    > subscriber's reuse of the HTTP2 session:
    >     > for dynamic subscriptions to a specific publisher, all subscriber URI 
    > GET
    > requests MUST use a common HTTP2 session for a particular DSCP value.
    >
    >     Is that really a MUST? I would understand a RECOMMENDED to enable the
    >     dependency and weighting within the subscription using the same DSCP.
    >     However, what are the reasons to mandate it, and I don't believe it is
    >     enforceable as the publisher can't determine that a receiver is the same
    >     instance as another receiver, at least not if I assume that the
    >     receivers are instances running in a virtualized environment.
    > <RR2> You are correct. What about:
    > for dynamic subscriptions to a specific publisher, it is recommended that 
    > all
    > subscriber URI GET requests use a common HTTP2 session for a particular
    > DSCP value.
    
    If you are rewriting the old sentence that had a MUST because different DSCP 
    needs different TCP connections as only a single DSCP can be applied per TCP 
    connection, I think you need to have these two issues separated. One for 
    stating the recommendation about reusing HTTP/2 sessions for multiple 
    subscriptions using the same DSCP value. A second one stating the requirement 
    that you need to use different HTTP/2 sessions for each DSCP value in use.
The text above was indeed for reusing HTTP2 sessions on the client/subscriber. I'll add text for the last part above too (different DSCP values can't share HTTP2 session).

Regards,
Reshad.

    
    Cheers
    
    Magnus Westerlund