RE: Notification

[Alex Rousskov <rousskov@xxxxxxxxxxxxxxxxxxxxxxx>]

On Tue, 8 Apr 2003, Abbie Barbir wrote:

> Yes, this should be the case. In this case, is Notification
> application Protocol dependent? Or is it done out of band, (this
> also addresses next paragraph too).

Does not matter at this point. Application dependency is a secondary
problem, IMO. First, we need to decide whether we should support
notification (on a protocol level) at all.

> Here are the IAB requirements:
>   (3.1) Notification: The overall OPES framework needs to assist
>    content providers in detecting and responding to client-centric
>    actions by OPES intermediaries that are deemed inappropriate by the
>    content provider.
>
>    (3.2) Notification: The overall OPES framework should assist end
>    users in detecting the behavior of OPES intermediaries, potentially
>    allowing them to identify imperfect or compromised intermediaries.

I believe tracing satisfies 3.2. The only problem is with 3.1 because
most client-centric actions happen _after_ the application message left
the content provider(s) and, thus, notifications cannot be piggy-backed
to application messages and have to travel in the opposite direction of
traces. Let's concentrate on satisfying 3.1 as the subject of this
thread.

The 3.1 requirement is quite vague and it is not clear how normative
are the comments that accompany/justify it. My vote is to interpret
"assist" above as "assistance on non-protocol level". That is, we
provide always-on tracing and claim that traces are sufficient to
satisfy 3.1 above as long as both ends cooperate. We can also assert
that if the ends do not cooperate, then no protocol-level solution
will work either. Specifically, we suggest that content providers that
suspect or experience difficulties do the following:

	1. Check whether requests they receive pass through
	  OPES intermediaries. Presence of OPES tracing info
	  will determine that. This check is only possible for
	  request/response protocols. For other protocols (e.g.,
	  broadcast or push), the provider would have to assume
	  that OPES intermediaries are involved until proven
	  otherwise.

	2. If OPES intermediaries are suspected,
	  request OPES traces from potentially affected user(s).
	  The trace will be a part of the application message
	  received by the user software. If users cooperate,
	  the provider(s) have all the information they need.
	  If users do not cooperate, the provider(s) cannot
	  do much about it (they might be able to deny service
	  to uncooperative users in some cases).

	3. Some traces may indicate that more information
	  is available by accessing certain resources on the
	  specified OPES intermediary or elsewhere. Content
	  providers may query for more information in that
	  case.

	4. If everything else fails, providers can enforce
	   no-adaptation policy using appropriate OPES
	   bypass mechanisms and/or end-to-end mechanisms.

Alex.